[PATCH v5 00/16] Device / Driver PCI / Platform Rust abstractions

[PATCH v5 00/16] Device / Driver PCI / Platform Rust abstractions

[Danilo Krummrich]

This patch series implements the necessary Rust abstractions to implement
device drivers in Rust.

This includes some basic generalizations for driver registration, handling of ID
tables, MMIO operations and device resource handling.

Those generalizations are used to implement device driver support for two
busses, the PCI and platform bus (with OF IDs) in order to provide some evidence
that the generalizations work as intended.

The patch series also includes two patches adding two driver samples, one PCI
driver and one platform driver.

The PCI bits are motivated by the Nova driver project [1], but are used by at
least one more OOT driver (rnvme [2]).

The platform bits, besides adding some more evidence to the base abstractions,
are required by a few more OOT drivers aiming at going upstream, i.e. rvkms [3],
cpufreq-dt [4], asahi [5] and the i2c work from Fabien [6].

The patches of this series can also be [7], [8] and [9].

Changes in v5:
==============
- Opaque:
  - add `Opaque::pin_init`

- Revocable:
  - use const generic instead of bool in `revoke_internal`
  - don't open code things with `Opaque::try_ffi_init`, use
    `Opaque::pin_init` instead

- Driver:
  - fix `DriverOps` -> `RegistrationOps` in commit message
  - fix signature of `register` and `unregister` to take an
    `Opaque<T::RegType>` instead of a mutable reference
  - implement generic `driver::Adapter`

- ID table:
  - fix `module_device_table!` macro, according to commit 054a9cd395a7
   (modpost: rename alias symbol for MODULE_DEVICE_TABLE())

- PCI:
  - remove `pci::DeviceId` argument from probe()
  - provide `vendor_id` and `device_id` accessor functions
  - use `addr_of_mut!` for the device in probe()

- OF:
  - move OF `IdTable` type alias from platform.rs to of.rs

- Platform:
  - use `addr_of_mut!` for the device in probe()
  - move generic OF code to `driver::Adapter`

- MISC:
  - rebase onto latest rust-next (-rc2)

Changes in v4:
==============
- Revocable
  - convert `Revocable::data` to `Opaque`
  - introduce `revoke_nosync`, which does not wait for an RCU grace period
  - fix minor typo

- Device ID
  - fix ID table export name to always be unique
  - remove `#![allow(stable_features)]`
  - move `#![allow(const_refs_to_cell)]` to the "stable in 1.83" list

- I/O
  - split `Io<SIZE>` in `IoRaw<SIZE>` and `Io<SIZE>`
  - add rust helper for ioremap() and iounmap() (needed by doctests)

- Devres
  - optimze `drop` by using `revoke_nosync` (we're guaranteed there are no more
    concurrent users, hence no need to wait for a full grace period)

- OF
  - rename "Open Firmware" -> "Device Tree / Open Firmware" (Rob)
  - remove unused C header reference
  - add TODO comment to loop in `DeviceId::new`
  - remove `DeviceId::compatible`; was only used in sample code
  - add missing `#[repr(transparent)]`
  - use #[cfg(CONFIG_OF)] for the relevant functions

- PCI
  - let Rust helper for pci_resource_len() return resource_size_t

- PCI Sample
  - remove unnecessary `from_le`

- Platform
  - fix example compatible string
  - add example for `platform::Driver`
  - rename `ID_TABLE` to `OF_ID_TABLE`
  - don't allow public use of `of_match_table`; convert to `of_id_info` to
    retrieve the `of::DeviceId` to gather the corresponding `IdInfo`
  - remove wrong example reference in the documentation of `platform::Driver`
  - remove `as_dev`, as we already implement `AsRef` for `platform::Device`

- Platform Sample
  - fix compatible string; add corresponding entry to drivers/of/unittest-data/tests-platform.dtsi
  - remove usage of `of_match_table`

- MISC
  - fix a few spelling mistakes
  - rebase onto rust-next (v6.13-rc1)

Changes in v3:
==============
- add commits for `Opaque::try_ffi_init` and `InPlaceModule`
- rename `DriverOps` to `RegistrationOps`
- rework device ID abstractions to get rid of almost all macro magic (thanks to
  Gary Guo for working this out!)
  - this is possible due to recently stabilized language features
- add modpost alias generation for device ID tables
  - unfortunately, this is the part that still requires some macro magic in the
    device ID abstractions
- PCI
  - represent the driver private data with the driver specific `Driver` instance
    and bind it's lifetime to the time of the driver being bound to a device
    - this allows us to handle class / subsystem registrations in a cleaner way
  - get rid of `Driver::remove`
    - Rust drivers should bind cleanup code to the `Drop` implementation of the
      corresponding structure instead and put it into their driver structure for
      automatic cleanup
  - add a sample PCI driver
- add abstractions for `struct of_device_id`
- add abstractions for the platform bus, including a sample driver
- update the MAINTAINERS file accordingly
  - currently this turns out a bit messy, but it should become better once the
    build system supports a treewide distribution of the kernel crate
  - I didn't add myself as maintainer, but (if requested) I'm willing to do so
    and help with maintenance

Changes in v2:
==============
- statically initialize driver structures (Greg)
- move base device ID abstractions to a separate source file (Greg)
- remove `DeviceRemoval` trait in favor of using a `Devres` callback to
  unregister drivers
- remove `device::Data`, we don't need this abstraction anymore now that we
  `Devres` to revoke resources and registrations
- pass the module name to `Module::init` and `InPlaceModule::init` in a separate
  patch
- rework of `Io` including compile time boundary checks (Miguel, Wedson)
- adjust PCI abstractions accordingly and implement a `module_pci_driver!` macro
- rework `pci::Bar` to support a const SIZE
- increase the total amount of Documentation, rephrase some safety comments and
  commit messages for less ambiguity
- fix compilation issues with some documentation examples

[1] https://gitlab.freedesktop.org/drm/nova/-/tree/nova-next
[2] https://github.com/metaspace/linux/tree/rnvme
[3] https://lore.kernel.org/all/20240930233257.1189730-1-lyude@redhat.com/
[4] https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git/log/?h=rust/cpufreq-dt
[5] https://github.com/AsahiLinux/linux
[6] https://github.com/Fabo/linux/tree/fparent/rust-i2c
[7] https://github.com/Rust-for-Linux/linux/tree/staging/rust-device
[8] https://github.com/Rust-for-Linux/linux/tree/staging/rust-pci
[9] https://github.com/Rust-for-Linux/linux/tree/staging/dev

Danilo Krummrich (14):
  rust: pass module name to `Module::init`
  rust: implement generic driver registration
  rust: implement `IdArray`, `IdTable` and `RawDeviceId`
  rust: types: add `Opaque::pin_init`
  rust: add `io::{Io, IoRaw}` base types
  rust: add devres abstraction
  rust: pci: add basic PCI device / driver abstractions
  rust: pci: implement I/O mappable `pci::Bar`
  samples: rust: add Rust PCI sample driver
  rust: of: add `of::DeviceId` abstraction
  rust: driver: implement `Adapter`
  rust: platform: add basic platform device / driver abstractions
  samples: rust: add Rust platform sample driver
  MAINTAINERS: add Danilo to DRIVER CORE

Wedson Almeida Filho (2):
  rust: add rcu abstraction
  rust: add `Revocable` type

 MAINTAINERS                                  |   9 +
 drivers/block/rnull.rs                       |   2 +-
 drivers/of/unittest-data/tests-platform.dtsi |   5 +
 rust/bindings/bindings_helper.h              |   3 +
 rust/helpers/device.c                        |  10 +
 rust/helpers/helpers.c                       |   5 +
 rust/helpers/io.c                            | 101 +++++
 rust/helpers/pci.c                           |  18 +
 rust/helpers/platform.c                      |  13 +
 rust/helpers/rcu.c                           |  13 +
 rust/kernel/device_id.rs                     | 165 +++++++
 rust/kernel/devres.rs                        | 179 ++++++++
 rust/kernel/driver.rs                        | 173 ++++++++
 rust/kernel/io.rs                            | 260 +++++++++++
 rust/kernel/lib.rs                           |  28 +-
 rust/kernel/net/phy.rs                       |   2 +-
 rust/kernel/of.rs                            |  60 +++
 rust/kernel/pci.rs                           | 438 +++++++++++++++++++
 rust/kernel/platform.rs                      | 193 ++++++++
 rust/kernel/revocable.rs                     | 223 ++++++++++
 rust/kernel/sync.rs                          |   1 +
 rust/kernel/sync/lock/global.rs              |   6 +-
 rust/kernel/sync/rcu.rs                      |  47 ++
 rust/kernel/types.rs                         |  11 +
 rust/macros/lib.rs                           |   6 +-
 rust/macros/module.rs                        |   7 +-
 samples/rust/Kconfig                         |  21 +
 samples/rust/Makefile                        |   2 +
 samples/rust/rust_driver_pci.rs              | 110 +++++
 samples/rust/rust_driver_platform.rs         |  49 +++
 samples/rust/rust_minimal.rs                 |   2 +-
 samples/rust/rust_print_main.rs              |   2 +-
 32 files changed, 2150 insertions(+), 14 deletions(-)
 create mode 100644 rust/helpers/device.c
 create mode 100644 rust/helpers/io.c
 create mode 100644 rust/helpers/pci.c
 create mode 100644 rust/helpers/platform.c
 create mode 100644 rust/helpers/rcu.c
 create mode 100644 rust/kernel/device_id.rs
 create mode 100644 rust/kernel/devres.rs
 create mode 100644 rust/kernel/driver.rs
 create mode 100644 rust/kernel/io.rs
 create mode 100644 rust/kernel/of.rs
 create mode 100644 rust/kernel/pci.rs
 create mode 100644 rust/kernel/platform.rs
 create mode 100644 rust/kernel/revocable.rs
 create mode 100644 rust/kernel/sync/rcu.rs
 create mode 100644 samples/rust/rust_driver_pci.rs
 create mode 100644 samples/rust/rust_driver_platform.rs


base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
-- 
2.47.0

[PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

In a subsequent patch we introduce the `Registration` abstraction used
to register driver structures. Some subsystems require the module name on
driver registration (e.g. PCI in __pci_register_driver()), hence pass
the module name to `Module::init`.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 drivers/block/rnull.rs          |  2 +-
 rust/kernel/lib.rs              | 14 ++++++++++----
 rust/kernel/net/phy.rs          |  2 +-
 rust/kernel/sync/lock/global.rs |  6 ++++--
 rust/macros/lib.rs              |  6 ++++--
 rust/macros/module.rs           |  7 +++++--
 samples/rust/rust_minimal.rs    |  2 +-
 samples/rust/rust_print_main.rs |  2 +-
 8 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/block/rnull.rs b/drivers/block/rnull.rs
index 9cca05dcf772..8e859dda70c3 100644
--- a/drivers/block/rnull.rs
+++ b/drivers/block/rnull.rs
@@ -37,7 +37,7 @@ struct NullBlkModule {
 }
 
 impl kernel::Module for NullBlkModule {
-    fn init(_module: &'static ThisModule) -> Result<Self> {
+    fn init(_name: &'static CStr, _module: &'static ThisModule) -> Result<Self> {
         pr_info!("Rust null_blk loaded\n");
         let tagset = Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
 
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e1065a7551a3..686db6aa3323 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -90,7 +90,7 @@ pub trait Module: Sized + Sync + Send {
     /// should do.
     ///
     /// Equivalent to the `module_init` macro in the C API.
-    fn init(module: &'static ThisModule) -> error::Result<Self>;
+    fn init(name: &'static str::CStr, module: &'static ThisModule) -> error::Result<Self>;
 }
 
 /// A module that is pinned and initialised in-place.
@@ -98,13 +98,19 @@ pub trait InPlaceModule: Sync + Send {
     /// Creates an initialiser for the module.
     ///
     /// It is called when the module is loaded.
-    fn init(module: &'static ThisModule) -> impl init::PinInit<Self, error::Error>;
+    fn init(
+        name: &'static str::CStr,
+        module: &'static ThisModule,
+    ) -> impl init::PinInit<Self, error::Error>;
 }
 
 impl<T: Module> InPlaceModule for T {
-    fn init(module: &'static ThisModule) -> impl init::PinInit<Self, error::Error> {
+    fn init(
+        name: &'static str::CStr,
+        module: &'static ThisModule,
+    ) -> impl init::PinInit<Self, error::Error> {
         let initer = move |slot: *mut Self| {
-            let m = <Self as Module>::init(module)?;
+            let m = <Self as Module>::init(name, module)?;
 
             // SAFETY: `slot` is valid for write per the contract with `pin_init_from_closure`.
             unsafe { slot.write(m) };
diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index b89c681d97c0..0f41df2e6b96 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -903,7 +903,7 @@ struct Module {
                 [$($crate::net::phy::create_phy_driver::<$driver>()),+];
 
             impl $crate::Module for Module {
-                fn init(module: &'static ThisModule) -> Result<Self> {
+                fn init(_name: &'static CStr, module: &'static ThisModule) -> Result<Self> {
                     // SAFETY: The anonymous constant guarantees that nobody else can access
                     // the `DRIVERS` static. The array is used only in the C side.
                     let drivers = unsafe { &mut DRIVERS };
diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
index 480ee724e3cc..feff4638e20b 100644
--- a/rust/kernel/sync/lock/global.rs
+++ b/rust/kernel/sync/lock/global.rs
@@ -187,6 +187,7 @@ pub fn get_mut(&mut self) -> &mut T {
 /// ```
 /// # mod ex {
 /// # use kernel::prelude::*;
+/// # use kernel::str;
 /// kernel::sync::global_lock! {
 ///     // SAFETY: Initialized in module initializer before first use.
 ///     unsafe(uninit) static MY_COUNTER: Mutex<u32> = 0;
@@ -199,7 +200,7 @@ pub fn get_mut(&mut self) -> &mut T {
 /// }
 ///
 /// impl kernel::Module for MyModule {
-///     fn init(_module: &'static ThisModule) -> Result<Self> {
+///     fn init(_name: &'static str::CStr, _module: &'static ThisModule) -> Result<Self> {
 ///         // SAFETY: Called exactly once.
 ///         unsafe { MY_COUNTER.init() };
 ///
@@ -216,6 +217,7 @@ pub fn get_mut(&mut self) -> &mut T {
 /// # mod ex {
 /// # use kernel::prelude::*;
 /// use kernel::sync::{GlobalGuard, GlobalLockedBy};
+/// # use kernel::str;
 ///
 /// kernel::sync::global_lock! {
 ///     // SAFETY: Initialized in module initializer before first use.
@@ -239,7 +241,7 @@ pub fn get_mut(&mut self) -> &mut T {
 /// }
 ///
 /// impl kernel::Module for MyModule {
-///     fn init(_module: &'static ThisModule) -> Result<Self> {
+///     fn init(_name: &'static str::CStr, _module: &'static ThisModule) -> Result<Self> {
 ///         // SAFETY: Called exactly once.
 ///         unsafe { MY_MUTEX.init() };
 ///
diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
index 4ab94e44adfe..d669f9cd1726 100644
--- a/rust/macros/lib.rs
+++ b/rust/macros/lib.rs
@@ -32,6 +32,7 @@
 ///
 /// ```
 /// use kernel::prelude::*;
+/// use kernel::str;
 ///
 /// module!{
 ///     type: MyModule,
@@ -45,7 +46,7 @@
 /// struct MyModule(i32);
 ///
 /// impl kernel::Module for MyModule {
-///     fn init(_module: &'static ThisModule) -> Result<Self> {
+///     fn init(_name: &'static str::CStr, _module: &'static ThisModule) -> Result<Self> {
 ///         let foo: i32 = 42;
 ///         pr_info!("I contain:  {}\n", foo);
 ///         Ok(Self(foo))
@@ -65,6 +66,7 @@
 ///
 /// ```
 /// use kernel::prelude::*;
+/// use kernel::str;
 ///
 /// module!{
 ///     type: MyDeviceDriverModule,
@@ -78,7 +80,7 @@
 /// struct MyDeviceDriverModule;
 ///
 /// impl kernel::Module for MyDeviceDriverModule {
-///     fn init(_module: &'static ThisModule) -> Result<Self> {
+///     fn init(_name: &'static str::CStr, _module: &'static ThisModule) -> Result<Self> {
 ///         Ok(Self)
 ///     }
 /// }
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 2587f41b0d39..1f14ef55341a 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -333,8 +333,11 @@ mod __module_init {{
                     ///
                     /// This function must only be called once.
                     unsafe fn __init() -> kernel::ffi::c_int {{
-                        let initer =
-                            <{type_} as kernel::InPlaceModule>::init(&super::super::THIS_MODULE);
+                        let initer = <{type_} as kernel::InPlaceModule>::init(
+                            kernel::c_str!(\"{name}\"),
+                            &super::super::THIS_MODULE
+                        );
+
                         // SAFETY: No data race, since `__MOD` can only be accessed by this module
                         // and there only `__init` and `__exit` access it. These functions are only
                         // called once and `__exit` cannot be called before or during `__init`.
diff --git a/samples/rust/rust_minimal.rs b/samples/rust/rust_minimal.rs
index 4aaf117bf8e3..1577dc34e563 100644
--- a/samples/rust/rust_minimal.rs
+++ b/samples/rust/rust_minimal.rs
@@ -17,7 +17,7 @@ struct RustMinimal {
 }
 
 impl kernel::Module for RustMinimal {
-    fn init(_module: &'static ThisModule) -> Result<Self> {
+    fn init(_name: &'static CStr, _module: &'static ThisModule) -> Result<Self> {
         pr_info!("Rust minimal sample (init)\n");
         pr_info!("Am I built-in? {}\n", !cfg!(MODULE));
 
diff --git a/samples/rust/rust_print_main.rs b/samples/rust/rust_print_main.rs
index aed90a6feecf..0853d767439b 100644
--- a/samples/rust/rust_print_main.rs
+++ b/samples/rust/rust_print_main.rs
@@ -41,7 +41,7 @@ fn arc_print() -> Result {
 }
 
 impl kernel::Module for RustPrint {
-    fn init(_module: &'static ThisModule) -> Result<Self> {
+    fn init(_name: &'static CStr, _module: &'static ThisModule) -> Result<Self> {
         pr_info!("Rust printing macros sample (init)\n");
 
         pr_emerg!("Emergency message (level 0) without args\n");
-- 
2.47.0

[PATCH v5 02/16] rust: implement generic driver registration

[Danilo Krummrich]

Implement the generic `Registration` type and the `RegistrationOps`
trait.

The `Registration` structure is the common type that represents a driver
registration and is typically bound to the lifetime of a module. However,
it doesn't implement actual calls to the kernel's driver core to register
drivers itself.

Instead the `RegistrationOps` trait is provided to subsystems, which have
to implement `RegistrationOps::register` and
`RegistrationOps::unregister`. Subsystems have to provide an
implementation for both of those methods where the subsystem specific
variants to register / unregister a driver have to implemented.

For instance, the PCI subsystem would call __pci_register_driver() from
`RegistrationOps::register` and pci_unregister_driver() from
`DrvierOps::unregister`.

Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS           |   1 +
 rust/kernel/driver.rs | 116 ++++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs    |   1 +
 3 files changed, 118 insertions(+)
 create mode 100644 rust/kernel/driver.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 17daa9ee9384..93fa6ec737c0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7033,6 +7033,7 @@ F:	include/linux/kobj*
 F:	include/linux/property.h
 F:	lib/kobj*
 F:	rust/kernel/device.rs
+F:	rust/kernel/driver.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
 M:	Nishanth Menon <nm@ti.com>
diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
new file mode 100644
index 000000000000..ab0bb46fe2cc
--- /dev/null
+++ b/rust/kernel/driver.rs
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic support for drivers of different buses (e.g., PCI, Platform, Amba, etc.).
+//!
+//! Each bus / subsystem is expected to implement [`RegistrationOps`], which allows drivers to
+//! register using the [`Registration`] class.
+
+use crate::error::{Error, Result};
+use crate::{init::PinInit, str::CStr, try_pin_init, types::Opaque, ThisModule};
+use core::pin::Pin;
+use macros::{pin_data, pinned_drop};
+
+/// The [`RegistrationOps`] trait serves as generic interface for subsystems (e.g., PCI, Platform,
+/// Amba, etc.) to provide the corresponding subsystem specific implementation to register /
+/// unregister a driver of the particular type (`RegType`).
+///
+/// For instance, the PCI subsystem would set `RegType` to `bindings::pci_driver` and call
+/// `bindings::__pci_register_driver` from `RegistrationOps::register` and
+/// `bindings::pci_unregister_driver` from `RegistrationOps::unregister`.
+pub trait RegistrationOps {
+    /// The type that holds information about the registration. This is typically a struct defined
+    /// by the C portion of the kernel.
+    type RegType: Default;
+
+    /// Registers a driver.
+    ///
+    /// On success, `reg` must remain pinned and valid until the matching call to
+    /// [`RegistrationOps::unregister`].
+    fn register(
+        reg: &Opaque<Self::RegType>,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result;
+
+    /// Unregisters a driver previously registered with [`RegistrationOps::register`].
+    fn unregister(reg: &Opaque<Self::RegType>);
+}
+
+/// A [`Registration`] is a generic type that represents the registration of some driver type (e.g.
+/// `bindings::pci_driver`). Therefore a [`Registration`] must be initialized with a type that
+/// implements the [`RegistrationOps`] trait, such that the generic `T::register` and
+/// `T::unregister` calls result in the subsystem specific registration calls.
+///
+///Once the `Registration` structure is dropped, the driver is unregistered.
+#[pin_data(PinnedDrop)]
+pub struct Registration<T: RegistrationOps> {
+    #[pin]
+    reg: Opaque<T::RegType>,
+}
+
+// SAFETY: `Registration` has no fields or methods accessible via `&Registration`, so it is safe to
+// share references to it with multiple threads as nothing can be done.
+unsafe impl<T: RegistrationOps> Sync for Registration<T> {}
+
+// SAFETY: Both registration and unregistration are implemented in C and safe to be performed from
+// any thread, so `Registration` is `Send`.
+unsafe impl<T: RegistrationOps> Send for Registration<T> {}
+
+impl<T: RegistrationOps> Registration<T> {
+    /// Creates a new instance of the registration object.
+    pub fn new(name: &'static CStr, module: &'static ThisModule) -> impl PinInit<Self, Error> {
+        try_pin_init!(Self {
+            reg <- Opaque::try_ffi_init(|ptr: *mut T::RegType| {
+                // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write.
+                unsafe { ptr.write(T::RegType::default()) };
+
+                // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write, and it has
+                // just been initialised above, so it's also valid for read.
+                let drv = unsafe { &*(ptr as *const Opaque<T::RegType>) };
+
+                T::register(drv, name, module)
+            }),
+        })
+    }
+}
+
+#[pinned_drop]
+impl<T: RegistrationOps> PinnedDrop for Registration<T> {
+    fn drop(self: Pin<&mut Self>) {
+        T::unregister(&self.reg);
+    }
+}
+
+/// A kernel module that only registers the given driver on init.
+///
+/// This is a helper struct to make it easier to define single-functionality modules, in this case,
+/// modules that offer a single driver.
+#[pin_data]
+pub struct Module<T: RegistrationOps> {
+    #[pin]
+    _driver: Registration<T>,
+}
+
+impl<T: RegistrationOps + Sync + Send> crate::InPlaceModule for Module<T> {
+    fn init(name: &'static CStr, module: &'static ThisModule) -> impl PinInit<Self, Error> {
+        try_pin_init!(Self {
+            _driver <- Registration::<T>::new(name, module),
+        })
+    }
+}
+
+/// Declares a kernel module that exposes a single driver.
+///
+/// It is meant to be used as a helper by other subsystems so they can more easily expose their own
+/// macros.
+#[macro_export]
+macro_rules! module_driver {
+    (<$gen_type:ident>, $driver_ops:ty, { type: $type:ty, $($f:tt)* }) => {
+        type Ops<$gen_type> = $driver_ops;
+        type ModuleType = $crate::driver::Module<Ops<$type>>;
+        $crate::prelude::module! {
+            type: ModuleType,
+            $($f)*
+        }
+    }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 686db6aa3323..0a719396256f 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -35,6 +35,7 @@
 mod build_assert;
 pub mod cred;
 pub mod device;
+pub mod driver;
 pub mod error;
 #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]
 pub mod firmware;
-- 
2.47.0

[PATCH v5 03/16] rust: implement `IdArray`, `IdTable` and `RawDeviceId`

[Danilo Krummrich]

Most subsystems use some kind of ID to match devices and drivers. Hence,
we have to provide Rust drivers an abstraction to register an ID table
for the driver to match.

Generally, those IDs are subsystem specific and hence need to be
implemented by the corresponding subsystem. However, the `IdArray`,
`IdTable` and `RawDeviceId` types provide a generalized implementation
that makes the life of subsystems easier to do so.

Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Fabien Parent <fabien.parent@linaro.org>
Signed-off-by: Fabien Parent <fabien.parent@linaro.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS              |   1 +
 rust/kernel/device_id.rs | 165 +++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs       |   6 ++
 3 files changed, 172 insertions(+)
 create mode 100644 rust/kernel/device_id.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 93fa6ec737c0..1c12722bbe9a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7033,6 +7033,7 @@ F:	include/linux/kobj*
 F:	include/linux/property.h
 F:	lib/kobj*
 F:	rust/kernel/device.rs
+F:	rust/kernel/device_id.rs
 F:	rust/kernel/driver.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
new file mode 100644
index 000000000000..e5859217a579
--- /dev/null
+++ b/rust/kernel/device_id.rs
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic implementation of device IDs.
+//!
+//! Each bus / subsystem that matches device and driver through a bus / subsystem specific ID is
+//! expected to implement [`RawDeviceId`].
+
+use core::mem::MaybeUninit;
+
+/// Marker trait to indicate a Rust device ID type represents a corresponding C device ID type.
+///
+/// This is meant to be implemented by buses/subsystems so that they can use [`IdTable`] to
+/// guarantee (at compile-time) zero-termination of device id tables provided by drivers.
+///
+/// # Safety
+///
+/// Implementers must ensure that:
+///   - `Self` is layout-compatible with [`RawDeviceId::RawType`]; i.e. it's safe to transmute to
+///     `RawDeviceId`.
+///
+///     This requirement is needed so `IdArray::new` can convert `Self` to `RawType` when building
+///     the ID table.
+///
+///     Ideally, this should be achieved using a const function that does conversion instead of
+///     transmute; however, const trait functions relies on `const_trait_impl` unstable feature,
+///     which is broken/gone in Rust 1.73.
+///
+///   - `DRIVER_DATA_OFFSET` is the offset of context/data field of the device ID (usually named
+///     `driver_data`) of the device ID, the field is suitable sized to write a `usize` value.
+///
+///     Similar to the previous requirement, the data should ideally be added during `Self` to
+///     `RawType` conversion, but there's currently no way to do it when using traits in const.
+pub unsafe trait RawDeviceId {
+    /// The raw type that holds the device id.
+    ///
+    /// Id tables created from [`Self`] are going to hold this type in its zero-terminated array.
+    type RawType: Copy;
+
+    /// The offset to the context/data field.
+    const DRIVER_DATA_OFFSET: usize;
+
+    /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceId`] trait.
+    fn index(&self) -> usize;
+}
+
+/// A zero-terminated device id array.
+#[repr(C)]
+pub struct RawIdArray<T: RawDeviceId, const N: usize> {
+    ids: [T::RawType; N],
+    sentinel: MaybeUninit<T::RawType>,
+}
+
+impl<T: RawDeviceId, const N: usize> RawIdArray<T, N> {
+    #[doc(hidden)]
+    pub const fn size(&self) -> usize {
+        core::mem::size_of::<Self>()
+    }
+}
+
+/// A zero-terminated device id array, followed by context data.
+#[repr(C)]
+pub struct IdArray<T: RawDeviceId, U, const N: usize> {
+    raw_ids: RawIdArray<T, N>,
+    id_infos: [U; N],
+}
+
+impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {
+    /// Creates a new instance of the array.
+    ///
+    /// The contents are derived from the given identifiers and context information.
+    pub const fn new(ids: [(T, U); N]) -> Self {
+        let mut raw_ids = [const { MaybeUninit::<T::RawType>::uninit() }; N];
+        let mut infos = [const { MaybeUninit::uninit() }; N];
+
+        let mut i = 0usize;
+        while i < N {
+            // SAFETY: by the safety requirement of `RawDeviceId`, we're guaranteed that `T` is
+            // layout-wise compatible with `RawType`.
+            raw_ids[i] = unsafe { core::mem::transmute_copy(&ids[i].0) };
+            // SAFETY: by the safety requirement of `RawDeviceId`, this would be effectively
+            // `raw_ids[i].driver_data = i;`.
+            unsafe {
+                raw_ids[i]
+                    .as_mut_ptr()
+                    .byte_offset(T::DRIVER_DATA_OFFSET as _)
+                    .cast::<usize>()
+                    .write(i);
+            }
+
+            // SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but
+            // later forget `ids`.
+            infos[i] = MaybeUninit::new(unsafe { core::ptr::read(&ids[i].1) });
+            i += 1;
+        }
+
+        core::mem::forget(ids);
+
+        Self {
+            raw_ids: RawIdArray {
+                // SAFETY: this is effectively `array_assume_init`, which is unstable, so we use
+                // `transmute_copy` instead. We have initialized all elements of `raw_ids` so this
+                // `array_assume_init` is safe.
+                ids: unsafe { core::mem::transmute_copy(&raw_ids) },
+                sentinel: MaybeUninit::zeroed(),
+            },
+            // SAFETY: We have initialized all elements of `infos` so this `array_assume_init` is
+            // safe.
+            id_infos: unsafe { core::mem::transmute_copy(&infos) },
+        }
+    }
+
+    /// Reference to the contained [`RawIdArray`].
+    pub const fn raw_ids(&self) -> &RawIdArray<T, N> {
+        &self.raw_ids
+    }
+}
+
+/// A device id table.
+///
+/// This trait is only implemented by `IdArray`.
+///
+/// The purpose of this trait is to allow `&'static dyn IdArray<T, U>` to be in context when `N` in
+/// `IdArray` doesn't matter.
+pub trait IdTable<T: RawDeviceId, U> {
+    /// Obtain the pointer to the ID table.
+    fn as_ptr(&self) -> *const T::RawType;
+
+    /// Obtain the pointer to the bus specific device ID from an index.
+    fn id(&self, index: usize) -> &T::RawType;
+
+    /// Obtain the pointer to the driver-specific information from an index.
+    fn info(&self, index: usize) -> &U;
+}
+
+impl<T: RawDeviceId, U, const N: usize> IdTable<T, U> for IdArray<T, U, N> {
+    fn as_ptr(&self) -> *const T::RawType {
+        // This cannot be `self.ids.as_ptr()`, as the return pointer must have correct provenance
+        // to access the sentinel.
+        (self as *const Self).cast()
+    }
+
+    fn id(&self, index: usize) -> &T::RawType {
+        &self.raw_ids.ids[index]
+    }
+
+    fn info(&self, index: usize) -> &U {
+        &self.id_infos[index]
+    }
+}
+
+/// Create device table alias for modpost.
+#[macro_export]
+macro_rules! module_device_table {
+    ($table_type: literal, $module_table_name:ident, $table_name:ident) => {
+        #[rustfmt::skip]
+        #[export_name =
+            concat!("__mod_device_table__", $table_type,
+                    "__", module_path!(),
+                    "_", line!(),
+                    "_", stringify!($table_name))
+        ]
+        static $module_table_name: [core::mem::MaybeUninit<u8>; $table_name.raw_ids().size()] =
+            unsafe { core::mem::transmute_copy($table_name.raw_ids()) };
+    };
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 0a719396256f..b5da7c520eb8 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -18,6 +18,11 @@
 #![feature(inline_const)]
 #![feature(lint_reasons)]
 #![feature(unsize)]
+// Stable in Rust 1.83
+#![feature(const_maybe_uninit_as_mut_ptr)]
+#![feature(const_mut_refs)]
+#![feature(const_ptr_write)]
+#![feature(const_refs_to_cell)]
 
 // Ensure conditional compilation based on the kernel configuration works;
 // otherwise we may silently break things like initcall handling.
@@ -35,6 +40,7 @@
 mod build_assert;
 pub mod cred;
 pub mod device;
+pub mod device_id;
 pub mod driver;
 pub mod error;
 #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]
-- 
2.47.0

[PATCH v5 04/16] rust: add rcu abstraction

[Danilo Krummrich]

From: Wedson Almeida Filho <wedsonaf@gmail.com>

Add a simple abstraction to guard critical code sections with an rcu
read lock.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/helpers/helpers.c  |  1 +
 rust/helpers/rcu.c      | 13 ++++++++++++
 rust/kernel/sync.rs     |  1 +
 rust/kernel/sync/rcu.rs | 47 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 62 insertions(+)
 create mode 100644 rust/helpers/rcu.c
 create mode 100644 rust/kernel/sync/rcu.rs

diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index dcf827a61b52..060750af6524 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -20,6 +20,7 @@
 #include "page.c"
 #include "pid_namespace.c"
 #include "rbtree.c"
+#include "rcu.c"
 #include "refcount.c"
 #include "security.c"
 #include "signal.c"
diff --git a/rust/helpers/rcu.c b/rust/helpers/rcu.c
new file mode 100644
index 000000000000..f1cec6583513
--- /dev/null
+++ b/rust/helpers/rcu.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/rcupdate.h>
+
+void rust_helper_rcu_read_lock(void)
+{
+	rcu_read_lock();
+}
+
+void rust_helper_rcu_read_unlock(void)
+{
+	rcu_read_unlock();
+}
diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 1eab7ebf25fd..0654008198b2 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -12,6 +12,7 @@
 pub mod lock;
 mod locked_by;
 pub mod poll;
+pub mod rcu;
 
 pub use arc::{Arc, ArcBorrow, UniqueArc};
 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs
new file mode 100644
index 000000000000..3beef70d5f34
--- /dev/null
+++ b/rust/kernel/sync/rcu.rs
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! RCU support.
+//!
+//! C header: [`include/linux/rcupdate.h`](srctree/include/linux/rcupdate.h)
+
+use crate::{bindings, types::NotThreadSafe};
+
+/// Evidence that the RCU read side lock is held on the current thread/CPU.
+///
+/// The type is explicitly not `Send` because this property is per-thread/CPU.
+///
+/// # Invariants
+///
+/// The RCU read side lock is actually held while instances of this guard exist.
+pub struct Guard(NotThreadSafe);
+
+impl Guard {
+    /// Acquires the RCU read side lock and returns a guard.
+    pub fn new() -> Self {
+        // SAFETY: An FFI call with no additional requirements.
+        unsafe { bindings::rcu_read_lock() };
+        // INVARIANT: The RCU read side lock was just acquired above.
+        Self(NotThreadSafe)
+    }
+
+    /// Explicitly releases the RCU read side lock.
+    pub fn unlock(self) {}
+}
+
+impl Default for Guard {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Drop for Guard {
+    fn drop(&mut self) {
+        // SAFETY: By the type invariants, the rcu read side is locked, so it is ok to unlock it.
+        unsafe { bindings::rcu_read_unlock() };
+    }
+}
+
+/// Acquires the RCU read side lock.
+pub fn read_lock() -> Guard {
+    Guard::new()
+}
-- 
2.47.0

[PATCH v5 05/16] rust: types: add `Opaque::pin_init`

[Danilo Krummrich]

Analogous to `Opaque::new` add `Opaque::pin_init`, which instead of a
value `T` takes a `PinInit<T>` and returns a `PinInit<Opaque<T>>`.

Suggested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/types.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index ec6457bb3084..3aea6af9a0bc 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -281,6 +281,17 @@ pub const fn uninit() -> Self {
         }
     }
 
+    /// Create an opaque pin-initializer from the given pin-initializer.
+    pub fn pin_init(slot: impl PinInit<T>) -> impl PinInit<Self> {
+        Self::ffi_init(|ptr: *mut T| {
+            // SAFETY:
+            //   - `ptr` is a valid pointer to uninitialized memory,
+            //   - `slot` is not accessed on error; the call is infallible,
+            //   - `slot` is pinned in memory.
+            let _ = unsafe { init::PinInit::<T>::__pinned_init(slot, ptr) };
+        })
+    }
+
     /// Creates a pin-initializer from the given initializer closure.
     ///
     /// The returned initializer calls the given closure with the pointer to the inner `T` of this
-- 
2.47.0

[PATCH v5 06/16] rust: add `Revocable` type

[Danilo Krummrich]

From: Wedson Almeida Filho <wedsonaf@gmail.com>

Revocable allows access to objects to be safely revoked at run time.

This is useful, for example, for resources allocated during device probe;
when the device is removed, the driver should stop accessing the device
resources even if another state is kept in memory due to existing
references (i.e., device context data is ref-counted and has a non-zero
refcount after removal of the device).

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/lib.rs       |   1 +
 rust/kernel/revocable.rs | 223 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 224 insertions(+)
 create mode 100644 rust/kernel/revocable.rs

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index b5da7c520eb8..200c5f99a805 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -60,6 +60,7 @@
 pub mod prelude;
 pub mod print;
 pub mod rbtree;
+pub mod revocable;
 pub mod security;
 pub mod seq_file;
 pub mod sizes;
diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
new file mode 100644
index 000000000000..e464d59eb6b5
--- /dev/null
+++ b/rust/kernel/revocable.rs
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Revocable objects.
+//!
+//! The [`Revocable`] type wraps other types and allows access to them to be revoked. The existence
+//! of a [`RevocableGuard`] ensures that objects remain valid.
+
+use crate::{bindings, prelude::*, sync::rcu, types::Opaque};
+use core::{
+    marker::PhantomData,
+    ops::Deref,
+    ptr::drop_in_place,
+    sync::atomic::{AtomicBool, Ordering},
+};
+
+/// An object that can become inaccessible at runtime.
+///
+/// Once access is revoked and all concurrent users complete (i.e., all existing instances of
+/// [`RevocableGuard`] are dropped), the wrapped object is also dropped.
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::revocable::Revocable;
+///
+/// struct Example {
+///     a: u32,
+///     b: u32,
+/// }
+///
+/// fn add_two(v: &Revocable<Example>) -> Option<u32> {
+///     let guard = v.try_access()?;
+///     Some(guard.a + guard.b)
+/// }
+///
+/// let v = KBox::pin_init(Revocable::new(Example { a: 10, b: 20 }), GFP_KERNEL).unwrap();
+/// assert_eq!(add_two(&v), Some(30));
+/// v.revoke();
+/// assert_eq!(add_two(&v), None);
+/// ```
+///
+/// Sample example as above, but explicitly using the rcu read side lock.
+///
+/// ```
+/// # use kernel::revocable::Revocable;
+/// use kernel::sync::rcu;
+///
+/// struct Example {
+///     a: u32,
+///     b: u32,
+/// }
+///
+/// fn add_two(v: &Revocable<Example>) -> Option<u32> {
+///     let guard = rcu::read_lock();
+///     let e = v.try_access_with_guard(&guard)?;
+///     Some(e.a + e.b)
+/// }
+///
+/// let v = KBox::pin_init(Revocable::new(Example { a: 10, b: 20 }), GFP_KERNEL).unwrap();
+/// assert_eq!(add_two(&v), Some(30));
+/// v.revoke();
+/// assert_eq!(add_two(&v), None);
+/// ```
+#[pin_data(PinnedDrop)]
+pub struct Revocable<T> {
+    is_available: AtomicBool,
+    #[pin]
+    data: Opaque<T>,
+}
+
+// SAFETY: `Revocable` is `Send` if the wrapped object is also `Send`. This is because while the
+// functionality exposed by `Revocable` can be accessed from any thread/CPU, it is possible that
+// this isn't supported by the wrapped object.
+unsafe impl<T: Send> Send for Revocable<T> {}
+
+// SAFETY: `Revocable` is `Sync` if the wrapped object is both `Send` and `Sync`. We require `Send`
+// from the wrapped object as well because  of `Revocable::revoke`, which can trigger the `Drop`
+// implementation of the wrapped object from an arbitrary thread.
+unsafe impl<T: Sync + Send> Sync for Revocable<T> {}
+
+impl<T> Revocable<T> {
+    /// Creates a new revocable instance of the given data.
+    pub fn new(data: impl PinInit<T>) -> impl PinInit<Self> {
+        pin_init!(Self {
+            is_available: AtomicBool::new(true),
+            data <- Opaque::pin_init(data),
+        })
+    }
+
+    /// Tries to access the revocable wrapped object.
+    ///
+    /// Returns `None` if the object has been revoked and is therefore no longer accessible.
+    ///
+    /// Returns a guard that gives access to the object otherwise; the object is guaranteed to
+    /// remain accessible while the guard is alive. In such cases, callers are not allowed to sleep
+    /// because another CPU may be waiting to complete the revocation of this object.
+    pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {
+        let guard = rcu::read_lock();
+        if self.is_available.load(Ordering::Relaxed) {
+            // Since `self.is_available` is true, data is initialised and has to remain valid
+            // because the RCU read side lock prevents it from being dropped.
+            Some(RevocableGuard::new(self.data.get(), guard))
+        } else {
+            None
+        }
+    }
+
+    /// Tries to access the revocable wrapped object.
+    ///
+    /// Returns `None` if the object has been revoked and is therefore no longer accessible.
+    ///
+    /// Returns a shared reference to the object otherwise; the object is guaranteed to
+    /// remain accessible while the rcu read side guard is alive. In such cases, callers are not
+    /// allowed to sleep because another CPU may be waiting to complete the revocation of this
+    /// object.
+    pub fn try_access_with_guard<'a>(&'a self, _guard: &'a rcu::Guard) -> Option<&'a T> {
+        if self.is_available.load(Ordering::Relaxed) {
+            // SAFETY: Since `self.is_available` is true, data is initialised and has to remain
+            // valid because the RCU read side lock prevents it from being dropped.
+            Some(unsafe { &*self.data.get() })
+        } else {
+            None
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Callers must ensure that there are no more concurrent users of the revocable object.
+    unsafe fn revoke_internal<const SYNC: bool>(&self) {
+        if self
+            .is_available
+            .compare_exchange(true, false, Ordering::Relaxed, Ordering::Relaxed)
+            .is_ok()
+        {
+            if SYNC {
+                // SAFETY: Just an FFI call, there are no further requirements.
+                unsafe { bindings::synchronize_rcu() };
+            }
+
+            // SAFETY: We know `self.data` is valid because only one CPU can succeed the
+            // `compare_exchange` above that takes `is_available` from `true` to `false`.
+            unsafe { drop_in_place(self.data.get()) };
+        }
+    }
+
+    /// Revokes access to and drops the wrapped object.
+    ///
+    /// Access to the object is revoked immediately to new callers of [`Revocable::try_access`],
+    /// expecting that there are no concurrent users of the object.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that there are no more concurrent users of the revocable object.
+    pub unsafe fn revoke_nosync(&self) {
+        // SAFETY: By the safety requirement of this function, the caller ensures that nobody is
+        // accessing the data anymore and hence we don't have to wait for the grace period to
+        // finish.
+        unsafe { self.revoke_internal::<false>() }
+    }
+
+    /// Revokes access to and drops the wrapped object.
+    ///
+    /// Access to the object is revoked immediately to new callers of [`Revocable::try_access`].
+    ///
+    /// If there are concurrent users of the object (i.e., ones that called
+    /// [`Revocable::try_access`] beforehand and still haven't dropped the returned guard), this
+    /// function waits for the concurrent access to complete before dropping the wrapped object.
+    pub fn revoke(&self) {
+        // SAFETY: By passing `true` we ask `revoke_internal` to wait for the grace period to
+        // finish.
+        unsafe { self.revoke_internal::<true>() }
+    }
+}
+
+#[pinned_drop]
+impl<T> PinnedDrop for Revocable<T> {
+    fn drop(self: Pin<&mut Self>) {
+        // Drop only if the data hasn't been revoked yet (in which case it has already been
+        // dropped).
+        // SAFETY: We are not moving out of `p`, only dropping in place
+        let p = unsafe { self.get_unchecked_mut() };
+        if *p.is_available.get_mut() {
+            // SAFETY: We know `self.data` is valid because no other CPU has changed
+            // `is_available` to `false` yet, and no other CPU can do it anymore because this CPU
+            // holds the only reference (mutable) to `self` now.
+            unsafe { drop_in_place(p.data.get()) };
+        }
+    }
+}
+
+/// A guard that allows access to a revocable object and keeps it alive.
+///
+/// CPUs may not sleep while holding on to [`RevocableGuard`] because it's in atomic context
+/// holding the RCU read-side lock.
+///
+/// # Invariants
+///
+/// The RCU read-side lock is held while the guard is alive.
+pub struct RevocableGuard<'a, T> {
+    data_ref: *const T,
+    _rcu_guard: rcu::Guard,
+    _p: PhantomData<&'a ()>,
+}
+
+impl<T> RevocableGuard<'_, T> {
+    fn new(data_ref: *const T, rcu_guard: rcu::Guard) -> Self {
+        Self {
+            data_ref,
+            _rcu_guard: rcu_guard,
+            _p: PhantomData,
+        }
+    }
+}
+
+impl<T> Deref for RevocableGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: By the type invariants, we hold the rcu read-side lock, so the object is
+        // guaranteed to remain valid.
+        unsafe { &*self.data_ref }
+    }
+}
-- 
2.47.0

[PATCH v5 07/16] rust: add `io::{Io, IoRaw}` base types

[Danilo Krummrich]

I/O memory is typically either mapped through direct calls to ioremap()
or subsystem / bus specific ones such as pci_iomap().

Even though subsystem / bus specific functions to map I/O memory are
based on ioremap() / iounmap() it is not desirable to re-implement them
in Rust.

Instead, implement a base type for I/O mapped memory, which generically
provides the corresponding accessors, such as `Io::readb` or
`Io:try_readb`.

`Io` supports an optional const generic, such that a driver can indicate
the minimal expected and required size of the mapping at compile time.
Correspondingly, calls to the 'non-try' accessors, support compile time
checks of the I/O memory offset to read / write, while the 'try'
accessors, provide boundary checks on runtime.

`IoRaw` is meant to be embedded into a structure (e.g. pci::Bar or
io::IoMem) which creates the actual I/O memory mapping and initializes
`IoRaw` accordingly.

To ensure that I/O mapped memory can't out-live the device it may be
bound to, subsystems must embed the corresponding I/O memory type (e.g.
pci::Bar) into a `Devres` container, such that it gets revoked once the
device is unbound.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/helpers/helpers.c |   1 +
 rust/helpers/io.c      | 101 ++++++++++++++++
 rust/kernel/io.rs      | 260 +++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs     |   1 +
 4 files changed, 363 insertions(+)
 create mode 100644 rust/helpers/io.c
 create mode 100644 rust/kernel/io.rs

diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 060750af6524..63f9b1da179f 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -14,6 +14,7 @@
 #include "cred.c"
 #include "err.c"
 #include "fs.c"
+#include "io.c"
 #include "jump_label.c"
 #include "kunit.c"
 #include "mutex.c"
diff --git a/rust/helpers/io.c b/rust/helpers/io.c
new file mode 100644
index 000000000000..1dde6374c0e2
--- /dev/null
+++ b/rust/helpers/io.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io.h>
+
+void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
+{
+	return ioremap(offset, size);
+}
+
+void rust_helper_iounmap(volatile void __iomem *addr)
+{
+	return iounmap(addr);
+}
+
+u8 rust_helper_readb(const volatile void __iomem *addr)
+{
+	return readb(addr);
+}
+
+u16 rust_helper_readw(const volatile void __iomem *addr)
+{
+	return readw(addr);
+}
+
+u32 rust_helper_readl(const volatile void __iomem *addr)
+{
+	return readl(addr);
+}
+
+#ifdef CONFIG_64BIT
+u64 rust_helper_readq(const volatile void __iomem *addr)
+{
+	return readq(addr);
+}
+#endif
+
+void rust_helper_writeb(u8 value, volatile void __iomem *addr)
+{
+	writeb(value, addr);
+}
+
+void rust_helper_writew(u16 value, volatile void __iomem *addr)
+{
+	writew(value, addr);
+}
+
+void rust_helper_writel(u32 value, volatile void __iomem *addr)
+{
+	writel(value, addr);
+}
+
+#ifdef CONFIG_64BIT
+void rust_helper_writeq(u64 value, volatile void __iomem *addr)
+{
+	writeq(value, addr);
+}
+#endif
+
+u8 rust_helper_readb_relaxed(const volatile void __iomem *addr)
+{
+	return readb_relaxed(addr);
+}
+
+u16 rust_helper_readw_relaxed(const volatile void __iomem *addr)
+{
+	return readw_relaxed(addr);
+}
+
+u32 rust_helper_readl_relaxed(const volatile void __iomem *addr)
+{
+	return readl_relaxed(addr);
+}
+
+#ifdef CONFIG_64BIT
+u64 rust_helper_readq_relaxed(const volatile void __iomem *addr)
+{
+	return readq_relaxed(addr);
+}
+#endif
+
+void rust_helper_writeb_relaxed(u8 value, volatile void __iomem *addr)
+{
+	writeb_relaxed(value, addr);
+}
+
+void rust_helper_writew_relaxed(u16 value, volatile void __iomem *addr)
+{
+	writew_relaxed(value, addr);
+}
+
+void rust_helper_writel_relaxed(u32 value, volatile void __iomem *addr)
+{
+	writel_relaxed(value, addr);
+}
+
+#ifdef CONFIG_64BIT
+void rust_helper_writeq_relaxed(u64 value, volatile void __iomem *addr)
+{
+	writeq_relaxed(value, addr);
+}
+#endif
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
new file mode 100644
index 000000000000..7ec3341bb411
--- /dev/null
+++ b/rust/kernel/io.rs
@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Memory-mapped IO.
+//!
+//! C header: [`include/asm-generic/io.h`](srctree/include/asm-generic/io.h)
+
+use crate::error::{code::EINVAL, Result};
+use crate::{bindings, build_assert};
+
+/// Raw representation of an MMIO region.
+///
+/// By itself, the existence of an instance of this structure does not provide any guarantees that
+/// the represented MMIO region does exist or is properly mapped.
+///
+/// Instead, the bus specific MMIO implementation must convert this raw representation into an `Io`
+/// instance providing the actual memory accessors. Only by the conversion into an `Io` structure
+/// any guarantees are given.
+pub struct IoRaw<const SIZE: usize = 0> {
+    addr: usize,
+    maxsize: usize,
+}
+
+impl<const SIZE: usize> IoRaw<SIZE> {
+    /// Returns a new `IoRaw` instance on success, an error otherwise.
+    pub fn new(addr: usize, maxsize: usize) -> Result<Self> {
+        if maxsize < SIZE {
+            return Err(EINVAL);
+        }
+
+        Ok(Self { addr, maxsize })
+    }
+
+    /// Returns the base address of the MMIO region.
+    #[inline]
+    pub fn addr(&self) -> usize {
+        self.addr
+    }
+
+    /// Returns the maximum size of the MMIO region.
+    #[inline]
+    pub fn maxsize(&self) -> usize {
+        self.maxsize
+    }
+}
+
+/// IO-mapped memory, starting at the base address @addr and spanning @maxlen bytes.
+///
+/// The creator (usually a subsystem / bus such as PCI) is responsible for creating the
+/// mapping, performing an additional region request etc.
+///
+/// # Invariant
+///
+/// `addr` is the start and `maxsize` the length of valid I/O mapped memory region of size
+/// `maxsize`.
+///
+/// # Examples
+///
+/// ```no_run
+/// # use kernel::{bindings, io::{Io, IoRaw}};
+/// # use core::ops::Deref;
+///
+/// // See also [`pci::Bar`] for a real example.
+/// struct IoMem<const SIZE: usize>(IoRaw<SIZE>);
+///
+/// impl<const SIZE: usize> IoMem<SIZE> {
+///     /// # Safety
+///     ///
+///     /// [`paddr`, `paddr` + `SIZE`) must be a valid MMIO region that is mappable into the CPUs
+///     /// virtual address space.
+///     unsafe fn new(paddr: usize) -> Result<Self>{
+///         // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is
+///         // valid for `ioremap`.
+///         let addr = unsafe { bindings::ioremap(paddr as _, SIZE.try_into().unwrap()) };
+///         if addr.is_null() {
+///             return Err(ENOMEM);
+///         }
+///
+///         Ok(IoMem(IoRaw::new(addr as _, SIZE)?))
+///     }
+/// }
+///
+/// impl<const SIZE: usize> Drop for IoMem<SIZE> {
+///     fn drop(&mut self) {
+///         // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.
+///         unsafe { bindings::iounmap(self.0.addr() as _); };
+///     }
+/// }
+///
+/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
+///    type Target = Io<SIZE>;
+///
+///    fn deref(&self) -> &Self::Target {
+///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
+///         unsafe { Io::from_raw(&self.0) }
+///    }
+/// }
+///
+///# fn no_run() -> Result<(), Error> {
+/// // SAFETY: Invalid usage for example purposes.
+/// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD)? };
+/// iomem.writel(0x42, 0x0);
+/// assert!(iomem.try_writel(0x42, 0x0).is_ok());
+/// assert!(iomem.try_writel(0x42, 0x4).is_err());
+/// # Ok(())
+/// # }
+/// ```
+#[repr(transparent)]
+pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
+
+macro_rules! define_read {
+    ($(#[$attr:meta])* $name:ident, $try_name:ident, $type_name:ty) => {
+        /// Read IO data from a given offset known at compile time.
+        ///
+        /// Bound checks are performed on compile time, hence if the offset is not known at compile
+        /// time, the build will fail.
+        $(#[$attr])*
+        #[inline]
+        pub fn $name(&self, offset: usize) -> $type_name {
+            let addr = self.io_addr_assert::<$type_name>(offset);
+
+            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+            unsafe { bindings::$name(addr as _) }
+        }
+
+        /// Read IO data from a given offset.
+        ///
+        /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
+        /// out of bounds.
+        $(#[$attr])*
+        pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
+            let addr = self.io_addr::<$type_name>(offset)?;
+
+            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+            Ok(unsafe { bindings::$name(addr as _) })
+        }
+    };
+}
+
+macro_rules! define_write {
+    ($(#[$attr:meta])* $name:ident, $try_name:ident, $type_name:ty) => {
+        /// Write IO data from a given offset known at compile time.
+        ///
+        /// Bound checks are performed on compile time, hence if the offset is not known at compile
+        /// time, the build will fail.
+        $(#[$attr])*
+        #[inline]
+        pub fn $name(&self, value: $type_name, offset: usize) {
+            let addr = self.io_addr_assert::<$type_name>(offset);
+
+            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+            unsafe { bindings::$name(value, addr as _, ) }
+        }
+
+        /// Write IO data from a given offset.
+        ///
+        /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
+        /// out of bounds.
+        $(#[$attr])*
+        pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
+            let addr = self.io_addr::<$type_name>(offset)?;
+
+            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+            unsafe { bindings::$name(value, addr as _) }
+            Ok(())
+        }
+    };
+}
+
+impl<const SIZE: usize> Io<SIZE> {
+    /// Converts an `IoRaw` into an `Io` instance, providing the accessors to the MMIO mapping.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
+    /// `maxsize`.
+    pub unsafe fn from_raw(raw: &IoRaw<SIZE>) -> &Self {
+        // SAFETY: `Io` is a transparent wrapper around `IoRaw`.
+        unsafe { &*core::ptr::from_ref(raw).cast() }
+    }
+
+    /// Returns the base address of this mapping.
+    #[inline]
+    pub fn addr(&self) -> usize {
+        self.0.addr()
+    }
+
+    /// Returns the maximum size of this mapping.
+    #[inline]
+    pub fn maxsize(&self) -> usize {
+        self.0.maxsize()
+    }
+
+    #[inline]
+    const fn offset_valid<U>(offset: usize, size: usize) -> bool {
+        let type_size = core::mem::size_of::<U>();
+        if let Some(end) = offset.checked_add(type_size) {
+            end <= size && offset % type_size == 0
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    fn io_addr<U>(&self, offset: usize) -> Result<usize> {
+        if !Self::offset_valid::<U>(offset, self.maxsize()) {
+            return Err(EINVAL);
+        }
+
+        // Probably no need to check, since the safety requirements of `Self::new` guarantee that
+        // this can't overflow.
+        self.addr().checked_add(offset).ok_or(EINVAL)
+    }
+
+    #[inline]
+    fn io_addr_assert<U>(&self, offset: usize) -> usize {
+        build_assert!(Self::offset_valid::<U>(offset, SIZE));
+
+        self.addr() + offset
+    }
+
+    define_read!(readb, try_readb, u8);
+    define_read!(readw, try_readw, u16);
+    define_read!(readl, try_readl, u32);
+    define_read!(
+        #[cfg(CONFIG_64BIT)]
+        readq,
+        try_readq,
+        u64
+    );
+
+    define_read!(readb_relaxed, try_readb_relaxed, u8);
+    define_read!(readw_relaxed, try_readw_relaxed, u16);
+    define_read!(readl_relaxed, try_readl_relaxed, u32);
+    define_read!(
+        #[cfg(CONFIG_64BIT)]
+        readq_relaxed,
+        try_readq_relaxed,
+        u64
+    );
+
+    define_write!(writeb, try_writeb, u8);
+    define_write!(writew, try_writew, u16);
+    define_write!(writel, try_writel, u32);
+    define_write!(
+        #[cfg(CONFIG_64BIT)]
+        writeq,
+        try_writeq,
+        u64
+    );
+
+    define_write!(writeb_relaxed, try_writeb_relaxed, u8);
+    define_write!(writew_relaxed, try_writew_relaxed, u16);
+    define_write!(writel_relaxed, try_writel_relaxed, u32);
+    define_write!(
+        #[cfg(CONFIG_64BIT)]
+        writeq_relaxed,
+        try_writeq_relaxed,
+        u64
+    );
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 200c5f99a805..d1f30b1a05fb 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -79,6 +79,7 @@
 
 #[doc(hidden)]
 pub use bindings;
+pub mod io;
 pub use macros;
 pub use uapi;
 
-- 
2.47.0

[PATCH v5 08/16] rust: add devres abstraction

[Danilo Krummrich]

Add a Rust abstraction for the kernel's devres (device resource
management) implementation.

The Devres type acts as a container to manage the lifetime and
accessibility of device bound resources. Therefore it registers a
devres callback and revokes access to the resource on invocation.

Users of the Devres abstraction can simply free the corresponding
resources in their Drop implementation, which is invoked when either the
Devres instance goes out of scope or the devres callback leads to the
resource being revoked, which implies a call to drop_in_place().

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS            |   1 +
 rust/helpers/device.c  |  10 +++
 rust/helpers/helpers.c |   1 +
 rust/kernel/devres.rs  | 179 +++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs     |   1 +
 5 files changed, 192 insertions(+)
 create mode 100644 rust/helpers/device.c
 create mode 100644 rust/kernel/devres.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 1c12722bbe9a..3658d3eb921c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7034,6 +7034,7 @@ F:	include/linux/property.h
 F:	lib/kobj*
 F:	rust/kernel/device.rs
 F:	rust/kernel/device_id.rs
+F:	rust/kernel/devres.rs
 F:	rust/kernel/driver.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
diff --git a/rust/helpers/device.c b/rust/helpers/device.c
new file mode 100644
index 000000000000..b2135c6686b0
--- /dev/null
+++ b/rust/helpers/device.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/device.h>
+
+int rust_helper_devm_add_action(struct device *dev,
+				void (*action)(void *),
+				void *data)
+{
+	return devm_add_action(dev, action, data);
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 63f9b1da179f..a3b52aa021de 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -12,6 +12,7 @@
 #include "build_assert.c"
 #include "build_bug.c"
 #include "cred.c"
+#include "device.c"
 #include "err.c"
 #include "fs.c"
 #include "io.c"
diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
new file mode 100644
index 000000000000..57ddb49fde1d
--- /dev/null
+++ b/rust/kernel/devres.rs
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Devres abstraction
+//!
+//! [`Devres`] represents an abstraction for the kernel devres (device resource management)
+//! implementation.
+
+use crate::{
+    alloc::Flags,
+    bindings,
+    device::Device,
+    error::{Error, Result},
+    prelude::*,
+    revocable::Revocable,
+    sync::Arc,
+};
+
+use core::ffi::c_void;
+use core::ops::Deref;
+
+#[pin_data]
+struct DevresInner<T> {
+    #[pin]
+    data: Revocable<T>,
+}
+
+/// This abstraction is meant to be used by subsystems to containerize [`Device`] bound resources to
+/// manage their lifetime.
+///
+/// [`Device`] bound resources should be freed when either the resource goes out of scope or the
+/// [`Device`] is unbound respectively, depending on what happens first.
+///
+/// To achieve that [`Devres`] registers a devres callback on creation, which is called once the
+/// [`Device`] is unbound, revoking access to the encapsulated resource (see also [`Revocable`]).
+///
+/// After the [`Devres`] has been unbound it is not possible to access the encapsulated resource
+/// anymore.
+///
+/// [`Devres`] users should make sure to simply free the corresponding backing resource in `T`'s
+/// [`Drop`] implementation.
+///
+/// # Example
+///
+/// ```no_run
+/// # use kernel::{bindings, c_str, device::Device, devres::Devres, io::{Io, IoRaw}};
+/// # use core::ops::Deref;
+///
+/// // See also [`pci::Bar`] for a real example.
+/// struct IoMem<const SIZE: usize>(IoRaw<SIZE>);
+///
+/// impl<const SIZE: usize> IoMem<SIZE> {
+///     /// # Safety
+///     ///
+///     /// [`paddr`, `paddr` + `SIZE`) must be a valid MMIO region that is mappable into the CPUs
+///     /// virtual address space.
+///     unsafe fn new(paddr: usize) -> Result<Self>{
+///         // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is
+///         // valid for `ioremap`.
+///         let addr = unsafe { bindings::ioremap(paddr as _, SIZE.try_into().unwrap()) };
+///         if addr.is_null() {
+///             return Err(ENOMEM);
+///         }
+///
+///         Ok(IoMem(IoRaw::new(addr as _, SIZE)?))
+///     }
+/// }
+///
+/// impl<const SIZE: usize> Drop for IoMem<SIZE> {
+///     fn drop(&mut self) {
+///         // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.
+///         unsafe { bindings::iounmap(self.0.addr() as _); };
+///     }
+/// }
+///
+/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
+///    type Target = Io<SIZE>;
+///
+///    fn deref(&self) -> &Self::Target {
+///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
+///         unsafe { Io::from_raw(&self.0) }
+///    }
+/// }
+/// # fn no_run() -> Result<(), Error> {
+/// # // SAFETY: Invalid usage; just for the example to get an `ARef<Device>` instance.
+/// # let dev = unsafe { Device::get_device(core::ptr::null_mut()) };
+///
+/// // SAFETY: Invalid usage for example purposes.
+/// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD)? };
+/// let devres = Devres::new(&dev, iomem, GFP_KERNEL)?;
+///
+/// let res = devres.try_access().ok_or(ENXIO)?;
+/// res.writel(0x42, 0x0);
+/// # Ok(())
+/// # }
+/// ```
+pub struct Devres<T>(Arc<DevresInner<T>>);
+
+impl<T> DevresInner<T> {
+    fn new(dev: &Device, data: T, flags: Flags) -> Result<Arc<DevresInner<T>>> {
+        let inner = Arc::pin_init(
+            pin_init!( DevresInner {
+                data <- Revocable::new(data),
+            }),
+            flags,
+        )?;
+
+        // Convert `Arc<DevresInner>` into a raw pointer and make devres own this reference until
+        // `Self::devres_callback` is called.
+        let data = inner.clone().into_raw();
+
+        // SAFETY: `devm_add_action` guarantees to call `Self::devres_callback` once `dev` is
+        // detached.
+        let ret = unsafe {
+            bindings::devm_add_action(dev.as_raw(), Some(Self::devres_callback), data as _)
+        };
+
+        if ret != 0 {
+            // SAFETY: We just created another reference to `inner` in order to pass it to
+            // `bindings::devm_add_action`. If `bindings::devm_add_action` fails, we have to drop
+            // this reference accordingly.
+            let _ = unsafe { Arc::from_raw(data) };
+            return Err(Error::from_errno(ret));
+        }
+
+        Ok(inner)
+    }
+
+    #[allow(clippy::missing_safety_doc)]
+    unsafe extern "C" fn devres_callback(ptr: *mut c_void) {
+        let ptr = ptr as *mut DevresInner<T>;
+        // Devres owned this memory; now that we received the callback, drop the `Arc` and hence the
+        // reference.
+        // SAFETY: Safe, since we leaked an `Arc` reference to devm_add_action() in
+        //         `DevresInner::new`.
+        let inner = unsafe { Arc::from_raw(ptr) };
+
+        inner.data.revoke();
+    }
+}
+
+impl<T> Devres<T> {
+    /// Creates a new [`Devres`] instance of the given `data`. The `data` encapsulated within the
+    /// returned `Devres` instance' `data` will be revoked once the device is detached.
+    pub fn new(dev: &Device, data: T, flags: Flags) -> Result<Self> {
+        let inner = DevresInner::new(dev, data, flags)?;
+
+        Ok(Devres(inner))
+    }
+
+    /// Same as [`Devres::new`], but does not return a `Devres` instance. Instead the given `data`
+    /// is owned by devres and will be revoked / dropped, once the device is detached.
+    pub fn new_foreign_owned(dev: &Device, data: T, flags: Flags) -> Result {
+        let _ = DevresInner::new(dev, data, flags)?;
+
+        Ok(())
+    }
+}
+
+impl<T> Deref for Devres<T> {
+    type Target = Revocable<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0.data
+    }
+}
+
+impl<T> Drop for Devres<T> {
+    fn drop(&mut self) {
+        // Revoke the data, such that it gets dropped already and the actual resource is freed.
+        //
+        // `DevresInner` has to stay alive until the devres callback has been called. This is
+        // necessary since we don't know when `Devres` is dropped and calling
+        // `devm_remove_action()` instead could race with `devres_release_all()`.
+        //
+        // SAFETY: When `drop` runs, it's guaranteed that nobody is accessing the revocable data
+        // anymore, hence it is safe not to wait for the grace period to finish.
+        unsafe { self.revoke_nosync() };
+    }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index d1f30b1a05fb..4b94e6072c63 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -41,6 +41,7 @@
 pub mod cred;
 pub mod device;
 pub mod device_id;
+pub mod devres;
 pub mod driver;
 pub mod error;
 #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]
-- 
2.47.0

[PATCH v5 09/16] rust: pci: add basic PCI device / driver abstractions

[Danilo Krummrich]

Implement the basic PCI abstractions required to write a basic PCI
driver. This includes the following data structures:

The `pci::Driver` trait represents the interface to the driver and
provides `pci::Driver::probe` for the driver to implement.

The `pci::Device` abstraction represents a `struct pci_dev` and provides
abstractions for common functions, such as `pci::Device::set_master`.

In order to provide the PCI specific parts to a generic
`driver::Registration` the `driver::RegistrationOps` trait is implemented
by `pci::Adapter`.

`pci::DeviceId` implements PCI device IDs based on the generic
`device_id::RawDevceId` abstraction.

Co-developed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS                     |   1 +
 rust/bindings/bindings_helper.h |   1 +
 rust/helpers/helpers.c          |   1 +
 rust/helpers/pci.c              |  18 ++
 rust/kernel/lib.rs              |   2 +
 rust/kernel/pci.rs              | 298 ++++++++++++++++++++++++++++++++
 6 files changed, 321 insertions(+)
 create mode 100644 rust/helpers/pci.c
 create mode 100644 rust/kernel/pci.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 3658d3eb921c..c20469f46801 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18102,6 +18102,7 @@ F:	include/asm-generic/pci*
 F:	include/linux/of_pci.h
 F:	include/linux/pci*
 F:	include/uapi/linux/pci*
+F:	rust/kernel/pci.rs
 
 PCIE BANDWIDTH CONTROLLER
 M:	Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 5c4dfe22f41a..6d7a68e2ecb7 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -20,6 +20,7 @@
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
 #include <linux/miscdevice.h>
+#include <linux/pci.h>
 #include <linux/phy.h>
 #include <linux/pid_namespace.h>
 #include <linux/poll.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index a3b52aa021de..3fda33cd42d4 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -20,6 +20,7 @@
 #include "kunit.c"
 #include "mutex.c"
 #include "page.c"
+#include "pci.c"
 #include "pid_namespace.c"
 #include "rbtree.c"
 #include "rcu.c"
diff --git a/rust/helpers/pci.c b/rust/helpers/pci.c
new file mode 100644
index 000000000000..8ba22f911459
--- /dev/null
+++ b/rust/helpers/pci.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/pci.h>
+
+void rust_helper_pci_set_drvdata(struct pci_dev *pdev, void *data)
+{
+	pci_set_drvdata(pdev, data);
+}
+
+void *rust_helper_pci_get_drvdata(struct pci_dev *pdev)
+{
+	return pci_get_drvdata(pdev);
+}
+
+resource_size_t rust_helper_pci_resource_len(struct pci_dev *pdev, int bar)
+{
+	return pci_resource_len(pdev, bar);
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 4b94e6072c63..07770add5ee2 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -82,6 +82,8 @@
 pub use bindings;
 pub mod io;
 pub use macros;
+#[cfg(all(CONFIG_PCI, CONFIG_PCI_MSI))]
+pub mod pci;
 pub use uapi;
 
 #[doc(hidden)]
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
new file mode 100644
index 000000000000..238eed06f388
--- /dev/null
+++ b/rust/kernel/pci.rs
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstractions for the PCI bus.
+//!
+//! C header: [`include/linux/pci.h`](srctree/include/linux/pci.h)
+
+use crate::{
+    bindings, container_of, device,
+    device_id::RawDeviceId,
+    driver,
+    error::{to_result, Result},
+    str::CStr,
+    types::{ARef, ForeignOwnable, Opaque},
+    ThisModule,
+};
+use core::{ops::Deref, ptr::addr_of_mut};
+use kernel::prelude::*;
+
+/// An adapter for the registration of PCI drivers.
+pub struct Adapter<T: Driver>(T);
+
+impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
+    type RegType = bindings::pci_driver;
+
+    fn register(
+        pdrv: &Opaque<Self::RegType>,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result {
+        // SAFETY: It's safe to set the fields of `struct pci_driver` on initialization.
+        unsafe {
+            (*pdrv.get()).name = name.as_char_ptr();
+            (*pdrv.get()).probe = Some(Self::probe_callback);
+            (*pdrv.get()).remove = Some(Self::remove_callback);
+            (*pdrv.get()).id_table = T::ID_TABLE.as_ptr();
+        }
+
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        to_result(unsafe {
+            bindings::__pci_register_driver(pdrv.get(), module.0, name.as_char_ptr())
+        })
+    }
+
+    fn unregister(pdrv: &Opaque<Self::RegType>) {
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        unsafe { bindings::pci_unregister_driver(pdrv.get()) }
+    }
+}
+
+impl<T: Driver + 'static> Adapter<T> {
+    extern "C" fn probe_callback(
+        pdev: *mut bindings::pci_dev,
+        id: *const bindings::pci_device_id,
+    ) -> core::ffi::c_int {
+        // SAFETY: The PCI bus only ever calls the probe callback with a valid pointer to a
+        // `struct pci_dev`.
+        let dev = unsafe { device::Device::get_device(addr_of_mut!((*pdev).dev)) };
+        // SAFETY: `dev` is guaranteed to be embedded in a valid `struct pci_dev` by the call
+        // above.
+        let mut pdev = unsafe { Device::from_dev(dev) };
+
+        // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct pci_device_id` and
+        // does not add additional invariants, so it's safe to transmute.
+        let id = unsafe { &*id.cast::<DeviceId>() };
+        let info = T::ID_TABLE.info(id.index());
+
+        match T::probe(&mut pdev, info) {
+            Ok(data) => {
+                // Let the `struct pci_dev` own a reference of the driver's private data.
+                // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
+                // `struct pci_dev`.
+                unsafe { bindings::pci_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
+            }
+            Err(err) => return Error::to_errno(err),
+        }
+
+        0
+    }
+
+    extern "C" fn remove_callback(pdev: *mut bindings::pci_dev) {
+        // SAFETY: The PCI bus only ever calls the remove callback with a valid pointer to a
+        // `struct pci_dev`.
+        let ptr = unsafe { bindings::pci_get_drvdata(pdev) };
+
+        // SAFETY: `remove_callback` is only ever called after a successful call to
+        // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
+        // `KBox<T>` pointer created through `KBox::into_foreign`.
+        let _ = unsafe { KBox::<T>::from_foreign(ptr) };
+    }
+}
+
+/// Declares a kernel module that exposes a single PCI driver.
+///
+/// # Example
+///
+///```ignore
+/// kernel::module_pci_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     author: "Author name",
+///     description: "Description",
+///     license: "GPL v2",
+/// }
+///```
+#[macro_export]
+macro_rules! module_pci_driver {
+($($f:tt)*) => {
+    $crate::module_driver!(<T>, $crate::pci::Adapter<T>, { $($f)* });
+};
+}
+
+/// Abstraction for bindings::pci_device_id.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::pci_device_id);
+
+impl DeviceId {
+    const PCI_ANY_ID: u32 = !0;
+
+    /// PCI_DEVICE macro.
+    pub const fn new(vendor: u32, device: u32) -> Self {
+        Self(bindings::pci_device_id {
+            vendor,
+            device,
+            subvendor: DeviceId::PCI_ANY_ID,
+            subdevice: DeviceId::PCI_ANY_ID,
+            class: 0,
+            class_mask: 0,
+            driver_data: 0,
+            override_only: 0,
+        })
+    }
+
+    /// PCI_DEVICE_CLASS macro.
+    pub const fn with_class(class: u32, class_mask: u32) -> Self {
+        Self(bindings::pci_device_id {
+            vendor: DeviceId::PCI_ANY_ID,
+            device: DeviceId::PCI_ANY_ID,
+            subvendor: DeviceId::PCI_ANY_ID,
+            subdevice: DeviceId::PCI_ANY_ID,
+            class,
+            class_mask,
+            driver_data: 0,
+            override_only: 0,
+        })
+    }
+}
+
+// Allow drivers R/O access to the fields of `pci_device_id`; should we prefer accessor functions
+// to void exposing C structure fields?
+impl Deref for DeviceId {
+    type Target = bindings::pci_device_id;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+// SAFETY:
+// * `DeviceId` is a `#[repr(transparent)` wrapper of `pci_device_id` and does not add
+//   additional invariants, so it's safe to transmute to `RawType`.
+// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::pci_device_id;
+
+    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::pci_device_id, driver_data);
+
+    fn index(&self) -> usize {
+        self.driver_data as _
+    }
+}
+
+/// IdTable type for PCI
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// Create a PCI `IdTable` with its alias for modpost.
+#[macro_export]
+macro_rules! pci_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::pci::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("pci", $module_table_name, $table_name);
+    };
+}
+
+/// The PCI driver trait.
+///
+/// # Example
+///
+///```
+/// # use kernel::{bindings, pci};
+///
+/// struct MyDriver;
+///
+/// kernel::pci_device_table!(
+///     PCI_TABLE,
+///     MODULE_PCI_TABLE,
+///     <MyDriver as pci::Driver>::IdInfo,
+///     [
+///         (pci::DeviceId::new(bindings::PCI_VENDOR_ID_REDHAT, bindings::PCI_ANY_ID as u32), ())
+///     ]
+/// );
+///
+/// impl pci::Driver for MyDriver {
+///     type IdInfo = ();
+///     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
+///
+///     fn probe(
+///         _pdev: &mut pci::Device,
+///         _id_info: &Self::IdInfo,
+///     ) -> Result<Pin<KBox<Self>>> {
+///         Err(ENODEV)
+///     }
+/// }
+///```
+/// Drivers must implement this trait in order to get a PCI driver registered. Please refer to the
+/// `Adapter` documentation for an example.
+pub trait Driver {
+    /// The type holding information about each device id supported by the driver.
+    ///
+    /// TODO: Use associated_type_defaults once stabilized:
+    ///
+    /// type IdInfo: 'static = ();
+    type IdInfo: 'static;
+
+    /// The table of device ids supported by the driver.
+    const ID_TABLE: IdTable<Self::IdInfo>;
+
+    /// PCI driver probe.
+    ///
+    /// Called when a new platform device is added or discovered.
+    /// Implementers should attempt to initialize the device here.
+    fn probe(dev: &mut Device, id_info: &Self::IdInfo) -> Result<Pin<KBox<Self>>>;
+}
+
+/// The PCI device representation.
+///
+/// A PCI device is based on an always reference counted `device:Device` instance. Cloning a PCI
+/// device, hence, also increments the base device' reference count.
+#[derive(Clone)]
+pub struct Device(ARef<device::Device>);
+
+impl Device {
+    /// Create a PCI Device instance from an existing `device::Device`.
+    ///
+    /// # Safety
+    ///
+    /// `dev` must be an `ARef<device::Device>` whose underlying `bindings::device` is a member of
+    /// a `bindings::pci_dev`.
+    pub unsafe fn from_dev(dev: ARef<device::Device>) -> Self {
+        Self(dev)
+    }
+
+    fn as_raw(&self) -> *mut bindings::pci_dev {
+        // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`
+        // embedded in `struct pci_dev`.
+        unsafe { container_of!(self.0.as_raw(), bindings::pci_dev, dev) as _ }
+    }
+
+    /// Returns the PCI vendor ID.
+    pub fn vendor_id(&self) -> u16 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
+        unsafe { (*self.as_raw()).vendor }
+    }
+
+    /// Returns the PCI device ID.
+    pub fn device_id(&self) -> u16 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
+        unsafe { (*self.as_raw()).device }
+    }
+
+    /// Enable memory resources for this device.
+    pub fn enable_device_mem(&self) -> Result {
+        // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
+        let ret = unsafe { bindings::pci_enable_device_mem(self.as_raw()) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Enable bus-mastering for this device.
+    pub fn set_master(&self) {
+        // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
+        unsafe { bindings::pci_set_master(self.as_raw()) };
+    }
+}
+
+impl AsRef<device::Device> for Device {
+    fn as_ref(&self) -> &device::Device {
+        &self.0
+    }
+}
-- 
2.47.0

[PATCH v5 10/16] rust: pci: implement I/O mappable `pci::Bar`

[Danilo Krummrich]

Implement `pci::Bar`, `pci::Device::iomap_region` and
`pci::Device::iomap_region_sized` to allow for I/O mappings of PCI BARs.

To ensure that a `pci::Bar`, and hence the I/O memory mapping, can't
out-live the PCI device, the `pci::Bar` type is always embedded into a
`Devres` container, such that the `pci::Bar` is revoked once the device
is unbound and hence the I/O mapped memory is unmapped.

A `pci::Bar` can be requested with (`pci::Device::iomap_region_sized`) or
without (`pci::Device::iomap_region`) a const generic representing the
minimal requested size of the I/O mapped memory region. In case of the
latter only runtime checked I/O reads / writes are possible.

Co-developed-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/pci.rs | 140 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 238eed06f388..a91f90585a1f 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -5,10 +5,14 @@
 //! C header: [`include/linux/pci.h`](srctree/include/linux/pci.h)
 
 use crate::{
+    alloc::flags::*,
     bindings, container_of, device,
     device_id::RawDeviceId,
+    devres::Devres,
     driver,
     error::{to_result, Result},
+    io::Io,
+    io::IoRaw,
     str::CStr,
     types::{ARef, ForeignOwnable, Opaque},
     ThisModule,
@@ -241,9 +245,115 @@ pub trait Driver {
 ///
 /// A PCI device is based on an always reference counted `device:Device` instance. Cloning a PCI
 /// device, hence, also increments the base device' reference count.
+///
+/// # Invariants
+///
+/// `Device` hold a valid reference of `ARef<device::Device>` whose underlying `struct device` is a
+/// member of a `struct pci_dev`.
 #[derive(Clone)]
 pub struct Device(ARef<device::Device>);
 
+/// A PCI BAR to perform I/O-Operations on.
+///
+/// # Invariants
+///
+/// `Bar` always holds an `IoRaw` inststance that holds a valid pointer to the start of the I/O
+/// memory mapped PCI bar and its size.
+pub struct Bar<const SIZE: usize = 0> {
+    pdev: Device,
+    io: IoRaw<SIZE>,
+    num: i32,
+}
+
+impl<const SIZE: usize> Bar<SIZE> {
+    fn new(pdev: Device, num: u32, name: &CStr) -> Result<Self> {
+        let len = pdev.resource_len(num)?;
+        if len == 0 {
+            return Err(ENOMEM);
+        }
+
+        // Convert to `i32`, since that's what all the C bindings use.
+        let num = i32::try_from(num)?;
+
+        // SAFETY:
+        // `pdev` is valid by the invariants of `Device`.
+        // `num` is checked for validity by a previous call to `Device::resource_len`.
+        // `name` is always valid.
+        let ret = unsafe { bindings::pci_request_region(pdev.as_raw(), num, name.as_char_ptr()) };
+        if ret != 0 {
+            return Err(EBUSY);
+        }
+
+        // SAFETY:
+        // `pdev` is valid by the invariants of `Device`.
+        // `num` is checked for validity by a previous call to `Device::resource_len`.
+        // `name` is always valid.
+        let ioptr: usize = unsafe { bindings::pci_iomap(pdev.as_raw(), num, 0) } as usize;
+        if ioptr == 0 {
+            // SAFETY:
+            // `pdev` valid by the invariants of `Device`.
+            // `num` is checked for validity by a previous call to `Device::resource_len`.
+            unsafe { bindings::pci_release_region(pdev.as_raw(), num) };
+            return Err(ENOMEM);
+        }
+
+        let io = match IoRaw::new(ioptr, len as usize) {
+            Ok(io) => io,
+            Err(err) => {
+                // SAFETY:
+                // `pdev` is valid by the invariants of `Device`.
+                // `ioptr` is guaranteed to be the start of a valid I/O mapped memory region.
+                // `num` is checked for validity by a previous call to `Device::resource_len`.
+                unsafe { Self::do_release(&pdev, ioptr, num) };
+                return Err(err);
+            }
+        };
+
+        Ok(Bar { pdev, io, num })
+    }
+
+    /// # Safety
+    ///
+    /// `ioptr` must be a valid pointer to the memory mapped PCI bar number `num`.
+    unsafe fn do_release(pdev: &Device, ioptr: usize, num: i32) {
+        // SAFETY:
+        // `pdev` is valid by the invariants of `Device`.
+        // `ioptr` is valid by the safety requirements.
+        // `num` is valid by the safety requirements.
+        unsafe {
+            bindings::pci_iounmap(pdev.as_raw(), ioptr as _);
+            bindings::pci_release_region(pdev.as_raw(), num);
+        }
+    }
+
+    fn release(&self) {
+        // SAFETY: The safety requirements are guaranteed by the type invariant of `self.pdev`.
+        unsafe { Self::do_release(&self.pdev, self.io.addr(), self.num) };
+    }
+}
+
+impl Bar {
+    fn index_is_valid(index: u32) -> bool {
+        // A `struct pci_dev` owns an array of resources with at most `PCI_NUM_RESOURCES` entries.
+        index < bindings::PCI_NUM_RESOURCES
+    }
+}
+
+impl<const SIZE: usize> Drop for Bar<SIZE> {
+    fn drop(&mut self) {
+        self.release();
+    }
+}
+
+impl<const SIZE: usize> Deref for Bar<SIZE> {
+    type Target = Io<SIZE>;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: By the type invariant of `Self`, the MMIO range in `self.io` is properly mapped.
+        unsafe { Io::from_raw(&self.io) }
+    }
+}
+
 impl Device {
     /// Create a PCI Device instance from an existing `device::Device`.
     ///
@@ -289,6 +399,36 @@ pub fn set_master(&self) {
         // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
         unsafe { bindings::pci_set_master(self.as_raw()) };
     }
+
+    /// Returns the size of the given PCI bar resource.
+    pub fn resource_len(&self, bar: u32) -> Result<bindings::resource_size_t> {
+        if !Bar::index_is_valid(bar) {
+            return Err(EINVAL);
+        }
+
+        // SAFETY:
+        // - `bar` is a valid bar number, as guaranteed by the above call to `Bar::index_is_valid`,
+        // - by its type invariant `self.as_raw` is always a valid pointer to a `struct pci_dev`.
+        Ok(unsafe { bindings::pci_resource_len(self.as_raw(), bar.try_into()?) })
+    }
+
+    /// Mapps an entire PCI-BAR after performing a region-request on it. I/O operation bound checks
+    /// can be performed on compile time for offsets (plus the requested type size) < SIZE.
+    pub fn iomap_region_sized<const SIZE: usize>(
+        &self,
+        bar: u32,
+        name: &CStr,
+    ) -> Result<Devres<Bar<SIZE>>> {
+        let bar = Bar::<SIZE>::new(self.clone(), bar, name)?;
+        let devres = Devres::new(self.as_ref(), bar, GFP_KERNEL)?;
+
+        Ok(devres)
+    }
+
+    /// Mapps an entire PCI-BAR after performing a region-request on it.
+    pub fn iomap_region(&self, bar: u32, name: &CStr) -> Result<Devres<Bar>> {
+        self.iomap_region_sized::<0>(bar, name)
+    }
 }
 
 impl AsRef<device::Device> for Device {
-- 
2.47.0

[PATCH v5 11/16] samples: rust: add Rust PCI sample driver

[Danilo Krummrich]

This commit adds a sample Rust PCI driver for QEMU's "pci-testdev"
device. To enable this device QEMU has to be called with
`-device pci-testdev`.

The same driver shows how to use the PCI device / driver abstractions,
as well as how to request and map PCI BARs, including a short sequence of
MMIO operations.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS                     |   1 +
 samples/rust/Kconfig            |  11 ++++
 samples/rust/Makefile           |   1 +
 samples/rust/rust_driver_pci.rs | 110 ++++++++++++++++++++++++++++++++
 4 files changed, 123 insertions(+)
 create mode 100644 samples/rust/rust_driver_pci.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index c20469f46801..50995e0e4252 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18103,6 +18103,7 @@ F:	include/linux/of_pci.h
 F:	include/linux/pci*
 F:	include/uapi/linux/pci*
 F:	rust/kernel/pci.rs
+F:	samples/rust/rust_driver_pci.rs
 
 PCIE BANDWIDTH CONTROLLER
 M:	Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index b0f74a81c8f9..6d468193cdd8 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -30,6 +30,17 @@ config SAMPLE_RUST_PRINT
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_DRIVER_PCI
+	tristate "PCI Driver"
+	depends on PCI
+	help
+	  This option builds the Rust PCI driver sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called driver_pci.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_HOSTPROGS
 	bool "Host programs"
 	help
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index c1a5c1655395..2f5b6bdb2fa5 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -3,6 +3,7 @@ ccflags-y += -I$(src)				# needed for trace events
 
 obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
 obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
+obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI)		+= rust_driver_pci.o
 
 rust_print-y := rust_print_main.o rust_print_events.o
 
diff --git a/samples/rust/rust_driver_pci.rs b/samples/rust/rust_driver_pci.rs
new file mode 100644
index 000000000000..94710b245834
--- /dev/null
+++ b/samples/rust/rust_driver_pci.rs
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust PCI driver sample (based on QEMU's `pci-testdev`).
+//!
+//! To make this driver probe, QEMU must be run with `-device pci-testdev`.
+
+use kernel::{bindings, c_str, devres::Devres, pci, prelude::*};
+
+struct Regs;
+
+impl Regs {
+    const TEST: usize = 0x0;
+    const OFFSET: usize = 0x4;
+    const DATA: usize = 0x8;
+    const COUNT: usize = 0xC;
+    const END: usize = 0x10;
+}
+
+type Bar0 = pci::Bar<{ Regs::END }>;
+
+#[derive(Debug)]
+struct TestIndex(u8);
+
+impl TestIndex {
+    const NO_EVENTFD: Self = Self(0);
+}
+
+struct SampleDriver {
+    pdev: pci::Device,
+    bar: Devres<Bar0>,
+}
+
+kernel::pci_device_table!(
+    PCI_TABLE,
+    MODULE_PCI_TABLE,
+    <SampleDriver as pci::Driver>::IdInfo,
+    [(
+        pci::DeviceId::new(bindings::PCI_VENDOR_ID_REDHAT, 0x5),
+        TestIndex::NO_EVENTFD
+    )]
+);
+
+impl SampleDriver {
+    fn testdev(index: &TestIndex, bar: &Bar0) -> Result<u32> {
+        // Select the test.
+        bar.writeb(index.0, Regs::TEST);
+
+        let offset = u32::from_le(bar.readl(Regs::OFFSET)) as usize;
+        let data = bar.readb(Regs::DATA);
+
+        // Write `data` to `offset` to increase `count` by one.
+        //
+        // Note that we need `try_writeb`, since `offset` can't be checked at compile-time.
+        bar.try_writeb(data, offset)?;
+
+        Ok(bar.readl(Regs::COUNT))
+    }
+}
+
+impl pci::Driver for SampleDriver {
+    type IdInfo = TestIndex;
+
+    const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
+
+    fn probe(pdev: &mut pci::Device, info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
+        dev_dbg!(
+            pdev.as_ref(),
+            "Probe Rust PCI driver sample (PCI ID: 0x{:x}, 0x{:x}).\n",
+            pdev.vendor_id(),
+            pdev.device_id()
+        );
+
+        pdev.enable_device_mem()?;
+        pdev.set_master();
+
+        let bar = pdev.iomap_region_sized::<{ Regs::END }>(0, c_str!("rust_driver_pci"))?;
+
+        let drvdata = KBox::new(
+            Self {
+                pdev: pdev.clone(),
+                bar,
+            },
+            GFP_KERNEL,
+        )?;
+
+        let bar = drvdata.bar.try_access().ok_or(ENXIO)?;
+
+        dev_info!(
+            pdev.as_ref(),
+            "pci-testdev data-match count: {}\n",
+            Self::testdev(info, &bar)?
+        );
+
+        Ok(drvdata.into())
+    }
+}
+
+impl Drop for SampleDriver {
+    fn drop(&mut self) {
+        dev_dbg!(self.pdev.as_ref(), "Remove Rust PCI driver sample.\n");
+    }
+}
+
+kernel::module_pci_driver! {
+    type: SampleDriver,
+    name: "rust_driver_pci",
+    author: "Danilo Krummrich",
+    description: "Rust PCI driver",
+    license: "GPL v2",
+}
-- 
2.47.0

[PATCH v5 12/16] rust: of: add `of::DeviceId` abstraction

[Danilo Krummrich]

`of::DeviceId` is an abstraction around `struct of_device_id`.

This is used by subsequent patches, in particular the platform bus
abstractions, to create OF device ID tables.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS        |  1 +
 rust/kernel/lib.rs |  1 +
 rust/kernel/of.rs  | 60 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 rust/kernel/of.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 50995e0e4252..7371ab484139 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17502,6 +17502,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git
 F:	Documentation/ABI/testing/sysfs-firmware-ofw
 F:	drivers/of/
 F:	include/linux/of*.h
+F:	rust/kernel/of.rs
 F:	scripts/dtc/
 F:	tools/testing/selftests/dt/
 K:	of_overlay_notifier_
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 07770add5ee2..7a0e4c82ad0c 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -56,6 +56,7 @@
 pub mod miscdevice;
 #[cfg(CONFIG_NET)]
 pub mod net;
+pub mod of;
 pub mod page;
 pub mod pid_namespace;
 pub mod prelude;
diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
new file mode 100644
index 000000000000..04f2d8ef29cb
--- /dev/null
+++ b/rust/kernel/of.rs
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Device Tree / Open Firmware abstractions.
+
+use crate::{bindings, device_id::RawDeviceId, prelude::*};
+
+/// IdTable type for OF drivers.
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// An open firmware device id.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::of_device_id);
+
+// SAFETY:
+// * `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and does not add
+//   additional invariants, so it's safe to transmute to `RawType`.
+// * `DRIVER_DATA_OFFSET` is the offset to the `data` field.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::of_device_id;
+
+    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::of_device_id, data);
+
+    fn index(&self) -> usize {
+        self.0.data as _
+    }
+}
+
+impl DeviceId {
+    /// Create a new device id from an OF 'compatible' string.
+    pub const fn new(compatible: &'static CStr) -> Self {
+        let src = compatible.as_bytes_with_nul();
+        // Replace with `bindings::of_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut of: bindings::of_device_id = unsafe { core::mem::zeroed() };
+
+        // TODO: Use `clone_from_slice` once the corresponding types do match.
+        let mut i = 0;
+        while i < src.len() {
+            of.compatible[i] = src[i] as _;
+            i += 1;
+        }
+
+        Self(of)
+    }
+}
+
+/// Create an OF `IdTable` with an "alias" for modpost.
+#[macro_export]
+macro_rules! of_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::of::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("of", $module_table_name, $table_name);
+    };
+}
-- 
2.47.0

[PATCH v5 13/16] rust: driver: implement `Adapter`

[Danilo Krummrich]

In order to not duplicate code in bus specific implementations (e.g.
platform), implement a generic `driver::Adapter` to represent the
connection of matched drivers and devices.

Bus specific `Adapter` implementations can simply implement this trait
to inherit generic functionality, such as matching OF or ACPI device IDs
and ID table entries.

Suggested-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/driver.rs | 59 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index ab0bb46fe2cc..d169899a5da1 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -6,7 +6,9 @@
 //! register using the [`Registration`] class.
 
 use crate::error::{Error, Result};
-use crate::{init::PinInit, str::CStr, try_pin_init, types::Opaque, ThisModule};
+use crate::{
+    device, device_id, init::PinInit, of, str::CStr, try_pin_init, types::Opaque, ThisModule,
+};
 use core::pin::Pin;
 use macros::{pin_data, pinned_drop};
 
@@ -114,3 +116,58 @@ macro_rules! module_driver {
         }
     }
 }
+
+/// The bus independent adapter to match a drivers and a devices.
+///
+/// This trait should be implemented by the bus specific adapter, which represents the connection
+/// of a device and a driver.
+///
+/// It provides bus independent functions for device / driver interactions.
+pub trait Adapter {
+    /// The type holding driver private data about each device id supported by the driver.
+    type IdInfo: 'static;
+
+    /// The [`of::IdTable`] of the corresponding driver.
+    fn of_id_table() -> of::IdTable<Self::IdInfo>;
+
+    /// Returns the driver's private data from the matching entry in the [`of::IdTable`], if any.
+    ///
+    /// If this returns `None`, it means there is no match with an entry in the [`of::IdTable`].
+    #[cfg(CONFIG_OF)]
+    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        let table = Self::of_id_table();
+
+        // SAFETY:
+        // - `table` has static lifetime, hence it's valid for read,
+        // - `dev` is guaranteed to be valid while it's alive, and so is `pdev.as_ref().as_raw()`.
+        let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
+
+        if raw_id.is_null() {
+            None
+        } else {
+            // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and
+            // does not add additional invariants, so it's safe to transmute.
+            let id = unsafe { &*raw_id.cast::<of::DeviceId>() };
+
+            Some(table.info(<of::DeviceId as device_id::RawDeviceId>::index(id)))
+        }
+    }
+
+    #[cfg(not(CONFIG_OF))]
+    fn of_id_info(_dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        None
+    }
+
+    /// Returns the driver's private data from the matching entry of any of the ID tables, if any.
+    ///
+    /// If this returns `None`, it means that there is no match in any of the ID tables directly
+    /// associated with a [`device::Device`].
+    fn id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        let id = Self::of_id_info(dev);
+        if id.is_some() {
+            return id;
+        }
+
+        None
+    }
+}
-- 
2.47.0

[PATCH v5 14/16] rust: platform: add basic platform device / driver abstractions

[Danilo Krummrich]

Implement the basic platform bus abstractions required to write a basic
platform driver. This includes the following data structures:

The `platform::Driver` trait represents the interface to the driver and
provides `platform::Driver::probe` for the driver to implement.

The `platform::Device` abstraction represents a `struct platform_device`.

In order to provide the platform bus specific parts to a generic
`driver::Registration` the `driver::RegistrationOps` trait is implemented
by `platform::Adapter`.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS                     |   1 +
 rust/bindings/bindings_helper.h |   2 +
 rust/helpers/helpers.c          |   1 +
 rust/helpers/platform.c         |  13 +++
 rust/kernel/lib.rs              |   1 +
 rust/kernel/platform.rs         | 193 ++++++++++++++++++++++++++++++++
 6 files changed, 211 insertions(+)
 create mode 100644 rust/helpers/platform.c
 create mode 100644 rust/kernel/platform.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 7371ab484139..a4253abb114b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7036,6 +7036,7 @@ F:	rust/kernel/device.rs
 F:	rust/kernel/device_id.rs
 F:	rust/kernel/devres.rs
 F:	rust/kernel/driver.rs
+F:	rust/kernel/platform.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
 M:	Nishanth Menon <nm@ti.com>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 6d7a68e2ecb7..e9fdceb568b8 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -20,9 +20,11 @@
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
 #include <linux/miscdevice.h>
+#include <linux/of_device.h>
 #include <linux/pci.h>
 #include <linux/phy.h>
 #include <linux/pid_namespace.h>
+#include <linux/platform_device.h>
 #include <linux/poll.h>
 #include <linux/refcount.h>
 #include <linux/sched.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 3fda33cd42d4..0640b7e115be 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -20,6 +20,7 @@
 #include "kunit.c"
 #include "mutex.c"
 #include "page.c"
+#include "platform.c"
 #include "pci.c"
 #include "pid_namespace.c"
 #include "rbtree.c"
diff --git a/rust/helpers/platform.c b/rust/helpers/platform.c
new file mode 100644
index 000000000000..ab9b9f317301
--- /dev/null
+++ b/rust/helpers/platform.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/platform_device.h>
+
+void *rust_helper_platform_get_drvdata(const struct platform_device *pdev)
+{
+	return platform_get_drvdata(pdev);
+}
+
+void rust_helper_platform_set_drvdata(struct platform_device *pdev, void *data)
+{
+	platform_set_drvdata(pdev, data);
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 7a0e4c82ad0c..cc8f48aa162b 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -59,6 +59,7 @@
 pub mod of;
 pub mod page;
 pub mod pid_namespace;
+pub mod platform;
 pub mod prelude;
 pub mod print;
 pub mod rbtree;
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
new file mode 100644
index 000000000000..a9b7e5259117
--- /dev/null
+++ b/rust/kernel/platform.rs
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Abstractions for the platform bus.
+//!
+//! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h)
+
+use crate::{
+    bindings, container_of, device, driver,
+    error::{to_result, Result},
+    of,
+    prelude::*,
+    str::CStr,
+    types::{ARef, ForeignOwnable, Opaque},
+    ThisModule,
+};
+
+use core::ptr::addr_of_mut;
+
+/// An adapter for the registration of platform drivers.
+pub struct Adapter<T: Driver>(T);
+
+impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
+    type RegType = bindings::platform_driver;
+
+    fn register(
+        pdrv: &Opaque<Self::RegType>,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result {
+        // SAFETY: It's safe to set the fields of `struct platform_driver` on initialization.
+        unsafe {
+            (*pdrv.get()).driver.name = name.as_char_ptr();
+            (*pdrv.get()).probe = Some(Self::probe_callback);
+            (*pdrv.get()).remove = Some(Self::remove_callback);
+            (*pdrv.get()).driver.of_match_table = T::OF_ID_TABLE.as_ptr();
+        }
+
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        to_result(unsafe { bindings::__platform_driver_register(pdrv.get(), module.0) })
+    }
+
+    fn unregister(pdrv: &Opaque<Self::RegType>) {
+        // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
+        unsafe { bindings::platform_driver_unregister(pdrv.get()) };
+    }
+}
+
+impl<T: Driver + 'static> Adapter<T> {
+    extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> core::ffi::c_int {
+        // SAFETY: The platform bus only ever calls the probe callback with a valid `pdev`.
+        let dev = unsafe { device::Device::get_device(addr_of_mut!((*pdev).dev)) };
+        // SAFETY: `dev` is guaranteed to be embedded in a valid `struct platform_device` by the
+        // call above.
+        let mut pdev = unsafe { Device::from_dev(dev) };
+
+        let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
+        match T::probe(&mut pdev, info) {
+            Ok(data) => {
+                // Let the `struct platform_device` own a reference of the driver's private data.
+                // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
+                // `struct platform_device`.
+                unsafe { bindings::platform_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
+            }
+            Err(err) => return Error::to_errno(err),
+        }
+
+        0
+    }
+
+    extern "C" fn remove_callback(pdev: *mut bindings::platform_device) {
+        // SAFETY: `pdev` is a valid pointer to a `struct platform_device`.
+        let ptr = unsafe { bindings::platform_get_drvdata(pdev) };
+
+        // SAFETY: `remove_callback` is only ever called after a successful call to
+        // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
+        // `KBox<T>` pointer created through `KBox::into_foreign`.
+        let _ = unsafe { KBox::<T>::from_foreign(ptr) };
+    }
+}
+
+impl<T: Driver + 'static> driver::Adapter for Adapter<T> {
+    type IdInfo = T::IdInfo;
+
+    fn of_id_table() -> of::IdTable<Self::IdInfo> {
+        T::OF_ID_TABLE
+    }
+}
+
+/// Declares a kernel module that exposes a single platform driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// kernel::module_platform_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     author: "Author name",
+///     description: "Description",
+///     license: "GPL v2",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_platform_driver {
+    ($($f:tt)*) => {
+        $crate::module_driver!(<T>, $crate::platform::Adapter<T>, { $($f)* });
+    };
+}
+
+/// The platform driver trait.
+///
+/// Drivers must implement this trait in order to get a platform driver registered.
+///
+/// # Example
+///
+///```
+/// # use kernel::{bindings, c_str, of, platform};
+///
+/// struct MyDriver;
+///
+/// kernel::of_device_table!(
+///     OF_TABLE,
+///     MODULE_OF_TABLE,
+///     <MyDriver as platform::Driver>::IdInfo,
+///     [
+///         (of::DeviceId::new(c_str!("test,device")), ())
+///     ]
+/// );
+///
+/// impl platform::Driver for MyDriver {
+///     type IdInfo = ();
+///     const OF_ID_TABLE: of::IdTable<Self::IdInfo> = &OF_TABLE;
+///
+///     fn probe(
+///         _pdev: &mut platform::Device,
+///         _id_info: Option<&Self::IdInfo>,
+///     ) -> Result<Pin<KBox<Self>>> {
+///         Err(ENODEV)
+///     }
+/// }
+///```
+pub trait Driver {
+    /// The type holding driver private data about each device id supported by the driver.
+    ///
+    /// TODO: Use associated_type_defaults once stabilized:
+    ///
+    /// type IdInfo: 'static = ();
+    type IdInfo: 'static;
+
+    /// The table of OF device ids supported by the driver.
+    const OF_ID_TABLE: of::IdTable<Self::IdInfo>;
+
+    /// Platform driver probe.
+    ///
+    /// Called when a new platform device is added or discovered.
+    /// Implementers should attempt to initialize the device here.
+    fn probe(dev: &mut Device, id_info: Option<&Self::IdInfo>) -> Result<Pin<KBox<Self>>>;
+}
+
+/// The platform device representation.
+///
+/// A platform device is based on an always reference counted `device:Device` instance. Cloning a
+/// platform device, hence, also increments the base device' reference count.
+///
+/// # Invariants
+///
+/// `Device` holds a valid reference of `ARef<device::Device>` whose underlying `struct device` is a
+/// member of a `struct platform_device`.
+#[derive(Clone)]
+pub struct Device(ARef<device::Device>);
+
+impl Device {
+    /// Convert a raw kernel device into a `Device`
+    ///
+    /// # Safety
+    ///
+    /// `dev` must be an `Aref<device::Device>` whose underlying `bindings::device` is a member of a
+    /// `bindings::platform_device`.
+    unsafe fn from_dev(dev: ARef<device::Device>) -> Self {
+        Self(dev)
+    }
+
+    fn as_raw(&self) -> *mut bindings::platform_device {
+        // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`
+        // embedded in `struct platform_device`.
+        unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) }.cast_mut()
+    }
+}
+
+impl AsRef<device::Device> for Device {
+    fn as_ref(&self) -> &device::Device {
+        &self.0
+    }
+}
-- 
2.47.0

[PATCH v5 15/16] samples: rust: add Rust platform sample driver

[Danilo Krummrich]

Add a sample Rust platform driver illustrating the usage of the platform
bus abstractions.

This driver probes through either a match of device / driver name or a
match within the OF ID table.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS                                  |  1 +
 drivers/of/unittest-data/tests-platform.dtsi |  5 ++
 samples/rust/Kconfig                         | 10 ++++
 samples/rust/Makefile                        |  1 +
 samples/rust/rust_driver_platform.rs         | 49 ++++++++++++++++++++
 5 files changed, 66 insertions(+)
 create mode 100644 samples/rust/rust_driver_platform.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index a4253abb114b..47b1a82dfdd0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7037,6 +7037,7 @@ F:	rust/kernel/device_id.rs
 F:	rust/kernel/devres.rs
 F:	rust/kernel/driver.rs
 F:	rust/kernel/platform.rs
+F:	samples/rust/rust_driver_platform.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
 M:	Nishanth Menon <nm@ti.com>
diff --git a/drivers/of/unittest-data/tests-platform.dtsi b/drivers/of/unittest-data/tests-platform.dtsi
index fa39611071b3..2caaf1c10ee6 100644
--- a/drivers/of/unittest-data/tests-platform.dtsi
+++ b/drivers/of/unittest-data/tests-platform.dtsi
@@ -33,6 +33,11 @@ dev@100 {
 					reg = <0x100>;
 				};
 			};
+
+			test-device@2 {
+				compatible = "test,rust-device";
+				reg = <0x2>;
+			};
 		};
 	};
 };
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 6d468193cdd8..70126b750426 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -41,6 +41,16 @@ config SAMPLE_RUST_DRIVER_PCI
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_DRIVER_PLATFORM
+	tristate "Platform Driver"
+	help
+	  This option builds the Rust Platform driver sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_driver_platform.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_HOSTPROGS
 	bool "Host programs"
 	help
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 2f5b6bdb2fa5..761d13fff018 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -4,6 +4,7 @@ ccflags-y += -I$(src)				# needed for trace events
 obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
 obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI)		+= rust_driver_pci.o
+obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM)	+= rust_driver_platform.o
 
 rust_print-y := rust_print_main.o rust_print_events.o
 
diff --git a/samples/rust/rust_driver_platform.rs b/samples/rust/rust_driver_platform.rs
new file mode 100644
index 000000000000..6ad59aa26eca
--- /dev/null
+++ b/samples/rust/rust_driver_platform.rs
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust Platform driver sample.
+
+use kernel::{c_str, of, platform, prelude::*};
+
+struct SampleDriver {
+    pdev: platform::Device,
+}
+
+struct Info(u32);
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <SampleDriver as platform::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("test,rust-device")), Info(42))]
+);
+
+impl platform::Driver for SampleDriver {
+    type IdInfo = Info;
+    const OF_ID_TABLE: of::IdTable<Self::IdInfo> = &OF_TABLE;
+
+    fn probe(pdev: &mut platform::Device, info: Option<&Self::IdInfo>) -> Result<Pin<KBox<Self>>> {
+        dev_dbg!(pdev.as_ref(), "Probe Rust Platform driver sample.\n");
+
+        if let Some(info) = info {
+            dev_info!(pdev.as_ref(), "Probed with info: '{}'.\n", info.0);
+        }
+
+        let drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;
+
+        Ok(drvdata.into())
+    }
+}
+
+impl Drop for SampleDriver {
+    fn drop(&mut self) {
+        dev_dbg!(self.pdev.as_ref(), "Remove Rust Platform driver sample.\n");
+    }
+}
+
+kernel::module_platform_driver! {
+    type: SampleDriver,
+    name: "rust_driver_platform",
+    author: "Danilo Krummrich",
+    description: "Rust Platform driver",
+    license: "GPL v2",
+}
-- 
2.47.0

[PATCH v5 16/16] MAINTAINERS: add Danilo to DRIVER CORE

[Danilo Krummrich]

Let's keep an eye on the Rust abstractions; add myself as reviewer to
DRIVER CORE.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 47b1a82dfdd0..ca3546f9f3b5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7021,6 +7021,7 @@ F:	include/linux/component.h
 DRIVER CORE, KOBJECTS, DEBUGFS AND SYSFS
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 R:	"Rafael J. Wysocki" <rafael@kernel.org>
+R:	Danilo Krummrich <dakr@kernel.org>
 S:	Supported
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
 F:	Documentation/core-api/kobject.rst
-- 
2.47.0

Re: [PATCH v5 05/16] rust: types: add `Opaque::pin_init`

[Alice Ryhl]

On Tue, Dec 10, 2024 at 11:50 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> Analogous to `Opaque::new` add `Opaque::pin_init`, which instead of a
> value `T` takes a `PinInit<T>` and returns a `PinInit<Opaque<T>>`.
>
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> In a subsequent patch we introduce the `Registration` abstraction used
> to register driver structures. Some subsystems require the module name on
> driver registration (e.g. PCI in __pci_register_driver()), hence pass
> the module name to `Module::init`.

Nit, we don't need the NAME of the PCI driver (well, we do like it, but
that's not the real thing), we want the pointer to the module structure
in the register_driver call.

Does this provide for that?  I'm thinking it does, but it's not the
"name" that is the issue here.

thanks,

greg k-h

Re: [PATCH v5 06/16] rust: add `Revocable` type

[Benoît du Garreau]

On Tue, 10 Dec 2024 23:46:33 +0100 Danilo Krummrich <dakr@kernel.org> wrote:

> From: Wedson Almeida Filho <wedsonaf@gmail.com>
>
> Revocable allows access to objects to be safely revoked at run time.
>
> This is useful, for example, for resources allocated during device probe;
> when the device is removed, the driver should stop accessing the device
> resources even if another state is kept in memory due to existing
> references (i.e., device context data is ref-counted and has a non-zero
> refcount after removal of the device).
>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Co-developed-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/lib.rs       |   1 +
>  rust/kernel/revocable.rs | 223 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 224 insertions(+)
>  create mode 100644 rust/kernel/revocable.rs
>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index b5da7c520eb8..200c5f99a805 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -60,6 +60,7 @@
>  pub mod prelude;
>  pub mod print;
>  pub mod rbtree;
> +pub mod revocable;
>  pub mod security;
>  pub mod seq_file;
>  pub mod sizes;
> diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
> new file mode 100644
> index 000000000000..e464d59eb6b5
> --- /dev/null
> +++ b/rust/kernel/revocable.rs
> @@ -0,0 +1,223 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Revocable objects.
> +//!
> +//! The [`Revocable`] type wraps other types and allows access to them to be revoked. The existence
> +//! of a [`RevocableGuard`] ensures that objects remain valid.
> +
> +use crate::{bindings, prelude::*, sync::rcu, types::Opaque};
> +use core::{
> +    marker::PhantomData,
> +    ops::Deref,
> +    ptr::drop_in_place,
> +    sync::atomic::{AtomicBool, Ordering},
> +};
> +
> +/// An object that can become inaccessible at runtime.
> +///
> +/// Once access is revoked and all concurrent users complete (i.e., all existing instances of
> +/// [`RevocableGuard`] are dropped), the wrapped object is also dropped.
> +///
> +/// # Examples
> +///
> +/// ```
> +/// # use kernel::revocable::Revocable;
> +///
> +/// struct Example {
> +///     a: u32,
> +///     b: u32,
> +/// }
> +///
> +/// fn add_two(v: &Revocable<Example>) -> Option<u32> {
> +///     let guard = v.try_access()?;
> +///     Some(guard.a + guard.b)
> +/// }
> +///
> +/// let v = KBox::pin_init(Revocable::new(Example { a: 10, b: 20 }), GFP_KERNEL).unwrap();
> +/// assert_eq!(add_two(&v), Some(30));
> +/// v.revoke();
> +/// assert_eq!(add_two(&v), None);
> +/// ```
> +///
> +/// Sample example as above, but explicitly using the rcu read side lock.
> +///
> +/// ```
> +/// # use kernel::revocable::Revocable;
> +/// use kernel::sync::rcu;
> +///
> +/// struct Example {
> +///     a: u32,
> +///     b: u32,
> +/// }
> +///
> +/// fn add_two(v: &Revocable<Example>) -> Option<u32> {
> +///     let guard = rcu::read_lock();
> +///     let e = v.try_access_with_guard(&guard)?;
> +///     Some(e.a + e.b)
> +/// }
> +///
> +/// let v = KBox::pin_init(Revocable::new(Example { a: 10, b: 20 }), GFP_KERNEL).unwrap();
> +/// assert_eq!(add_two(&v), Some(30));
> +/// v.revoke();
> +/// assert_eq!(add_two(&v), None);
> +/// ```
> +#[pin_data(PinnedDrop)]
> +pub struct Revocable<T> {
> +    is_available: AtomicBool,
> +    #[pin]
> +    data: Opaque<T>,
> +}
> +
> +// SAFETY: `Revocable` is `Send` if the wrapped object is also `Send`. This is because while the
> +// functionality exposed by `Revocable` can be accessed from any thread/CPU, it is possible that
> +// this isn't supported by the wrapped object.
> +unsafe impl<T: Send> Send for Revocable<T> {}
> +
> +// SAFETY: `Revocable` is `Sync` if the wrapped object is both `Send` and `Sync`. We require `Send`
> +// from the wrapped object as well because  of `Revocable::revoke`, which can trigger the `Drop`
> +// implementation of the wrapped object from an arbitrary thread.
> +unsafe impl<T: Sync + Send> Sync for Revocable<T> {}
> +
> +impl<T> Revocable<T> {
> +    /// Creates a new revocable instance of the given data.
> +    pub fn new(data: impl PinInit<T>) -> impl PinInit<Self> {
> +        pin_init!(Self {
> +            is_available: AtomicBool::new(true),
> +            data <- Opaque::pin_init(data),
> +        })
> +    }
> +
> +    /// Tries to access the revocable wrapped object.
> +    ///
> +    /// Returns `None` if the object has been revoked and is therefore no longer accessible.
> +    ///
> +    /// Returns a guard that gives access to the object otherwise; the object is guaranteed to
> +    /// remain accessible while the guard is alive. In such cases, callers are not allowed to sleep
> +    /// because another CPU may be waiting to complete the revocation of this object.
> +    pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {
> +        let guard = rcu::read_lock();
> +        if self.is_available.load(Ordering::Relaxed) {
> +            // Since `self.is_available` is true, data is initialised and has to remain valid
> +            // because the RCU read side lock prevents it from being dropped.
> +            Some(RevocableGuard::new(self.data.get(), guard))
> +        } else {
> +            None
> +        }
> +    }
> +
> +    /// Tries to access the revocable wrapped object.
> +    ///
> +    /// Returns `None` if the object has been revoked and is therefore no longer accessible.
> +    ///
> +    /// Returns a shared reference to the object otherwise; the object is guaranteed to
> +    /// remain accessible while the rcu read side guard is alive. In such cases, callers are not
> +    /// allowed to sleep because another CPU may be waiting to complete the revocation of this
> +    /// object.
> +    pub fn try_access_with_guard<'a>(&'a self, _guard: &'a rcu::Guard) -> Option<&'a T> {
> +        if self.is_available.load(Ordering::Relaxed) {
> +            // SAFETY: Since `self.is_available` is true, data is initialised and has to remain
> +            // valid because the RCU read side lock prevents it from being dropped.
> +            Some(unsafe { &*self.data.get() })
> +        } else {
> +            None
> +        }
> +    }
> +
> +    /// # Safety
> +    ///
> +    /// Callers must ensure that there are no more concurrent users of the revocable object.
> +    unsafe fn revoke_internal<const SYNC: bool>(&self) {
> +        if self
> +            .is_available
> +            .compare_exchange(true, false, Ordering::Relaxed, Ordering::Relaxed)
> +            .is_ok()

This can be simplified to `if self.is_available.swap(false, Ordering::Relaxed) {`

> +        {
> +            if SYNC {
> +                // SAFETY: Just an FFI call, there are no further requirements.
> +                unsafe { bindings::synchronize_rcu() };
> +            }
> +
> +            // SAFETY: We know `self.data` is valid because only one CPU can succeed the
> +            // `compare_exchange` above that takes `is_available` from `true` to `false`.
> +            unsafe { drop_in_place(self.data.get()) };
> +        }
> +    }
> +
> +    /// Revokes access to and drops the wrapped object.
> +    ///
> +    /// Access to the object is revoked immediately to new callers of [`Revocable::try_access`],
> +    /// expecting that there are no concurrent users of the object.
> +    ///
> +    /// # Safety
> +    ///
> +    /// Callers must ensure that there are no more concurrent users of the revocable object.
> +    pub unsafe fn revoke_nosync(&self) {
> +        // SAFETY: By the safety requirement of this function, the caller ensures that nobody is
> +        // accessing the data anymore and hence we don't have to wait for the grace period to
> +        // finish.
> +        unsafe { self.revoke_internal::<false>() }
> +    }
> +
> +    /// Revokes access to and drops the wrapped object.
> +    ///
> +    /// Access to the object is revoked immediately to new callers of [`Revocable::try_access`].
> +    ///
> +    /// If there are concurrent users of the object (i.e., ones that called
> +    /// [`Revocable::try_access`] beforehand and still haven't dropped the returned guard), this
> +    /// function waits for the concurrent access to complete before dropping the wrapped object.
> +    pub fn revoke(&self) {
> +        // SAFETY: By passing `true` we ask `revoke_internal` to wait for the grace period to
> +        // finish.
> +        unsafe { self.revoke_internal::<true>() }
> +    }
> +}
> +
> +#[pinned_drop]
> +impl<T> PinnedDrop for Revocable<T> {
> +    fn drop(self: Pin<&mut Self>) {
> +        // Drop only if the data hasn't been revoked yet (in which case it has already been
> +        // dropped).
> +        // SAFETY: We are not moving out of `p`, only dropping in place
> +        let p = unsafe { self.get_unchecked_mut() };
> +        if *p.is_available.get_mut() {
> +            // SAFETY: We know `self.data` is valid because no other CPU has changed
> +            // `is_available` to `false` yet, and no other CPU can do it anymore because this CPU
> +            // holds the only reference (mutable) to `self` now.
> +            unsafe { drop_in_place(p.data.get()) };
> +        }
> +    }
> +}
> +
> +/// A guard that allows access to a revocable object and keeps it alive.
> +///
> +/// CPUs may not sleep while holding on to [`RevocableGuard`] because it's in atomic context
> +/// holding the RCU read-side lock.
> +///
> +/// # Invariants
> +///
> +/// The RCU read-side lock is held while the guard is alive.
> +pub struct RevocableGuard<'a, T> {
> +    data_ref: *const T,
> +    _rcu_guard: rcu::Guard,
> +    _p: PhantomData<&'a ()>,
> +}

Shouldn't this type hold a `&'a T` directly instead of a raw pointer ?

> +
> +impl<T> RevocableGuard<'_, T> {
> +    fn new(data_ref: *const T, rcu_guard: rcu::Guard) -> Self {
> +        Self {
> +            data_ref,
> +            _rcu_guard: rcu_guard,
> +            _p: PhantomData,
> +        }
> +    }
> +}
> +
> +impl<T> Deref for RevocableGuard<'_, T> {
> +    type Target = T;
> +
> +    fn deref(&self) -> &Self::Target {
> +        // SAFETY: By the type invariants, we hold the rcu read-side lock, so the object is
> +        // guaranteed to remain valid.
> +        unsafe { &*self.data_ref }
> +    }
> +}
> --
> 2.47.0

Benoît du Garreau

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > In a subsequent patch we introduce the `Registration` abstraction used
> > to register driver structures. Some subsystems require the module name on
> > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > the module name to `Module::init`.
> 
> Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> that's not the real thing), we want the pointer to the module structure
> in the register_driver call.
> 
> Does this provide for that?  I'm thinking it does, but it's not the
> "name" that is the issue here.

Wait, no, you really do want the name, don't you.  You refer to
"module.0" to get the module structure pointer (if I'm reading the code
right), but as you have that pointer already, why can't you just use
module->name there as well as you have a pointer to a valid module
structure that has the name already embedded in it.

still confused,

greg k-h

Re: [PATCH v5 06/16] rust: add `Revocable` type

[Alice Ryhl]

On Wed, Dec 11, 2024 at 11:48 AM Benoît du Garreau <benoit@dugarreau.fr> wrote:
>
> On Tue, 10 Dec 2024 23:46:33 +0100 Danilo Krummrich <dakr@kernel.org> wrote:
> > +/// A guard that allows access to a revocable object and keeps it alive.
> > +///
> > +/// CPUs may not sleep while holding on to [`RevocableGuard`] because it's in atomic context
> > +/// holding the RCU read-side lock.
> > +///
> > +/// # Invariants
> > +///
> > +/// The RCU read-side lock is held while the guard is alive.
> > +pub struct RevocableGuard<'a, T> {
> > +    data_ref: *const T,
> > +    _rcu_guard: rcu::Guard,
> > +    _p: PhantomData<&'a ()>,
> > +}
>
> Shouldn't this type hold a `&'a T` directly instead of a raw pointer ?

No, because the value might get destroyed before the end of the
lifetime 'a. It's not legal to use references for containers that
might free or otherwise invalidate the referent in their destructor.

That said, the PhantomData field should probably be `&'a T`. It
doesn't actually change anything, but it carries the right intent.

Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > In a subsequent patch we introduce the `Registration` abstraction used
> > > to register driver structures. Some subsystems require the module name on
> > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > the module name to `Module::init`.
> > 
> > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > that's not the real thing), we want the pointer to the module structure
> > in the register_driver call.
> > 
> > Does this provide for that?  I'm thinking it does, but it's not the
> > "name" that is the issue here.
> 
> Wait, no, you really do want the name, don't you.  You refer to
> "module.0" to get the module structure pointer (if I'm reading the code
> right), but as you have that pointer already, why can't you just use
> module->name there as well as you have a pointer to a valid module
> structure that has the name already embedded in it.

In digging further, it's used by the pci code to call into lower layers,
but why it's using a different string other than the module name string
is beyond me.  Looks like this goes way back before git was around, and
odds are it's my fault for something I wrote a long time ago.

I'll see if I can just change the driver core to not need a name at all,
and pull it from the module which would make all of this go away in the
end.  Odds are something will break but who knows...

thanks,

greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > to register driver structures. Some subsystems require the module name on
> > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > the module name to `Module::init`.
> > > 
> > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > that's not the real thing), we want the pointer to the module structure
> > > in the register_driver call.
> > > 
> > > Does this provide for that?  I'm thinking it does, but it's not the
> > > "name" that is the issue here.
> > 
> > Wait, no, you really do want the name, don't you.  You refer to
> > "module.0" to get the module structure pointer (if I'm reading the code
> > right), but as you have that pointer already, why can't you just use
> > module->name there as well as you have a pointer to a valid module
> > structure that has the name already embedded in it.
> 
> In digging further, it's used by the pci code to call into lower layers,
> but why it's using a different string other than the module name string
> is beyond me.  Looks like this goes way back before git was around, and
> odds are it's my fault for something I wrote a long time ago.
> 
> I'll see if I can just change the driver core to not need a name at all,
> and pull it from the module which would make all of this go away in the
> end.  Odds are something will break but who knows...

Nope, things break, the "name" is there to handle built-in modules (as
the module pointer will be NULL.)

So what you really want is not the module->name (as I don't think that
will be set), but you want KBUILD_MODNAME which the build system sets.
You shouldn't need to pass the name through all of the subsystems here,
just rely on the build system instead.

Or does the Rust side not have KBUILD_MODNAME?

thanks,

greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Miguel Ojeda]

On Wed, Dec 11, 2024 at 12:05 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> Or does the Rust side not have KBUILD_MODNAME?

We can definitely give access to it at compile-time with e.g. `env!`:

    pr_info!("{}\n", env!("KBUILD_MODNAME"));

Cheers,
Miguel

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > to register driver structures. Some subsystems require the module name on
> > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > the module name to `Module::init`.
> > > > 
> > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > that's not the real thing), we want the pointer to the module structure
> > > > in the register_driver call.
> > > > 
> > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > "name" that is the issue here.
> > > 
> > > Wait, no, you really do want the name, don't you.  You refer to
> > > "module.0" to get the module structure pointer (if I'm reading the code
> > > right), but as you have that pointer already, why can't you just use
> > > module->name there as well as you have a pointer to a valid module
> > > structure that has the name already embedded in it.
> > 
> > In digging further, it's used by the pci code to call into lower layers,
> > but why it's using a different string other than the module name string
> > is beyond me.  Looks like this goes way back before git was around, and
> > odds are it's my fault for something I wrote a long time ago.
> > 
> > I'll see if I can just change the driver core to not need a name at all,
> > and pull it from the module which would make all of this go away in the
> > end.  Odds are something will break but who knows...
> 
> Nope, things break, the "name" is there to handle built-in modules (as
> the module pointer will be NULL.)
> 
> So what you really want is not the module->name (as I don't think that
> will be set), but you want KBUILD_MODNAME which the build system sets.

That's correct, and the reason why I pass through this name argument.

Sorry I wasn't able to reply earlier to save you some time.

> You shouldn't need to pass the name through all of the subsystems here,
> just rely on the build system instead.
> 
> Or does the Rust side not have KBUILD_MODNAME?

AFAIK, it doesn't (or didn't have at the time I wrote the patch).

@Miguel: Can we access KBUILD_MODNAME conveniently?

> 
> thanks,
> 
> greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > the module name to `Module::init`.
> > > > > 
> > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > that's not the real thing), we want the pointer to the module structure
> > > > > in the register_driver call.
> > > > > 
> > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > "name" that is the issue here.
> > > > 
> > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > right), but as you have that pointer already, why can't you just use
> > > > module->name there as well as you have a pointer to a valid module
> > > > structure that has the name already embedded in it.
> > > 
> > > In digging further, it's used by the pci code to call into lower layers,
> > > but why it's using a different string other than the module name string
> > > is beyond me.  Looks like this goes way back before git was around, and
> > > odds are it's my fault for something I wrote a long time ago.
> > > 
> > > I'll see if I can just change the driver core to not need a name at all,
> > > and pull it from the module which would make all of this go away in the
> > > end.  Odds are something will break but who knows...
> > 
> > Nope, things break, the "name" is there to handle built-in modules (as
> > the module pointer will be NULL.)
> > 
> > So what you really want is not the module->name (as I don't think that
> > will be set), but you want KBUILD_MODNAME which the build system sets.
> 
> That's correct, and the reason why I pass through this name argument.
> 
> Sorry I wasn't able to reply earlier to save you some time.
> 
> > You shouldn't need to pass the name through all of the subsystems here,
> > just rely on the build system instead.
> > 
> > Or does the Rust side not have KBUILD_MODNAME?
> 
> AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> 
> @Miguel: Can we access KBUILD_MODNAME conveniently?

Actually, I now remember there was another reason why I pass it through in
`Module::init`.

Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
won't get the KBUILD_MODNAME from the module that is using the bus abstraction.

> 
> > 
> > thanks,
> > 
> > greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Alice Ryhl]

On Wed, Dec 11, 2024 at 12:41 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Wed, Dec 11, 2024 at 12:05 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > Or does the Rust side not have KBUILD_MODNAME?
>
> We can definitely give access to it at compile-time with e.g. `env!`:
>
>     pr_info!("{}\n", env!("KBUILD_MODNAME"));

I guess the challenge is that we need that to get evaluated in the
driver, rather than inside the rust/kernel/ crate. Perhaps we could
have the module! macro emit something that attaches the name to the
module type, or something like that.

Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > the module name to `Module::init`.
> > > > > > 
> > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > in the register_driver call.
> > > > > > 
> > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > "name" that is the issue here.
> > > > > 
> > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > right), but as you have that pointer already, why can't you just use
> > > > > module->name there as well as you have a pointer to a valid module
> > > > > structure that has the name already embedded in it.
> > > > 
> > > > In digging further, it's used by the pci code to call into lower layers,
> > > > but why it's using a different string other than the module name string
> > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > odds are it's my fault for something I wrote a long time ago.
> > > > 
> > > > I'll see if I can just change the driver core to not need a name at all,
> > > > and pull it from the module which would make all of this go away in the
> > > > end.  Odds are something will break but who knows...
> > > 
> > > Nope, things break, the "name" is there to handle built-in modules (as
> > > the module pointer will be NULL.)
> > > 
> > > So what you really want is not the module->name (as I don't think that
> > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > 
> > That's correct, and the reason why I pass through this name argument.
> > 
> > Sorry I wasn't able to reply earlier to save you some time.
> > 
> > > You shouldn't need to pass the name through all of the subsystems here,
> > > just rely on the build system instead.
> > > 
> > > Or does the Rust side not have KBUILD_MODNAME?
> > 
> > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > 
> > @Miguel: Can we access KBUILD_MODNAME conveniently?
> 
> Actually, I now remember there was another reason why I pass it through in
> `Module::init`.
> 
> Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> won't get the KBUILD_MODNAME from the module that is using the bus abstraction.

Rust can't do that in a macro somehow that all pci rust drivers can pull
from?

thanks,

greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > the module name to `Module::init`.
> > > > > > > 
> > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > in the register_driver call.
> > > > > > > 
> > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > "name" that is the issue here.
> > > > > > 
> > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > structure that has the name already embedded in it.
> > > > > 
> > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > but why it's using a different string other than the module name string
> > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > 
> > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > and pull it from the module which would make all of this go away in the
> > > > > end.  Odds are something will break but who knows...
> > > > 
> > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > the module pointer will be NULL.)
> > > > 
> > > > So what you really want is not the module->name (as I don't think that
> > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > 
> > > That's correct, and the reason why I pass through this name argument.
> > > 
> > > Sorry I wasn't able to reply earlier to save you some time.
> > > 
> > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > just rely on the build system instead.
> > > > 
> > > > Or does the Rust side not have KBUILD_MODNAME?
> > > 
> > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > 
> > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > 
> > Actually, I now remember there was another reason why I pass it through in
> > `Module::init`.
> > 
> > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> 
> Rust can't do that in a macro somehow that all pci rust drivers can pull
> from?

The problem is that register / unregister is encapsulated within methods of the
abstraction types. So the C macro trick (while generally possible) isn't
applicable.

I think we could avoid having an additional `name` parameter in `Module::init`,
but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
passing it into the bus abstraction.

However, similar to what Alice suggested in another thread, we could include
this step in the `module_*_driver!` macros.

Modules that don't use this convenience macro would need to do it by hand
though. But that's probably not that big a deal.

> 
> thanks,
> 
> greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Alice Ryhl]

On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > the module name to `Module::init`.
> > > > > > > >
> > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > in the register_driver call.
> > > > > > > >
> > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > "name" that is the issue here.
> > > > > > >
> > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > structure that has the name already embedded in it.
> > > > > >
> > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > but why it's using a different string other than the module name string
> > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > >
> > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > and pull it from the module which would make all of this go away in the
> > > > > > end.  Odds are something will break but who knows...
> > > > >
> > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > the module pointer will be NULL.)
> > > > >
> > > > > So what you really want is not the module->name (as I don't think that
> > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > >
> > > > That's correct, and the reason why I pass through this name argument.
> > > >
> > > > Sorry I wasn't able to reply earlier to save you some time.
> > > >
> > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > just rely on the build system instead.
> > > > >
> > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > >
> > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > >
> > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > >
> > > Actually, I now remember there was another reason why I pass it through in
> > > `Module::init`.
> > >
> > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> >
> > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > from?
>
> The problem is that register / unregister is encapsulated within methods of the
> abstraction types. So the C macro trick (while generally possible) isn't
> applicable.
>
> I think we could avoid having an additional `name` parameter in `Module::init`,
> but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> passing it into the bus abstraction.
>
> However, similar to what Alice suggested in another thread, we could include
> this step in the `module_*_driver!` macros.
>
> Modules that don't use this convenience macro would need to do it by hand
> though. But that's probably not that big a deal.

I think we can do it in the core `module!` macro that everyone has to use.

Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 02:31:07PM +0100, Danilo Krummrich wrote:
> On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > the module name to `Module::init`.
> > > > > > > > 
> > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > in the register_driver call.
> > > > > > > > 
> > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > "name" that is the issue here.
> > > > > > > 
> > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > structure that has the name already embedded in it.
> > > > > > 
> > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > but why it's using a different string other than the module name string
> > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > 
> > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > and pull it from the module which would make all of this go away in the
> > > > > > end.  Odds are something will break but who knows...
> > > > > 
> > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > the module pointer will be NULL.)
> > > > > 
> > > > > So what you really want is not the module->name (as I don't think that
> > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > 
> > > > That's correct, and the reason why I pass through this name argument.
> > > > 
> > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > 
> > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > just rely on the build system instead.
> > > > > 
> > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > 
> > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > 
> > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > 
> > > Actually, I now remember there was another reason why I pass it through in
> > > `Module::init`.
> > > 
> > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > 
> > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > from?
> 
> The problem is that register / unregister is encapsulated within methods of the
> abstraction types. So the C macro trick (while generally possible) isn't
> applicable.

Really?  You can't have something in a required "register()" type function?
Something for when the driver "instance" is created as part of
pci::Driver?  You do that today in your sample driver for the id table:
	const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;

Something else called DRIVER_NAME that you could then set:
	const DRIVER_NAME: env!(KBUILD_MODNAME);

Also, I think you will want this for when a single module registers
multiple drivers which I think can happen at times, so you could
manually override the DRIVER_NAME field.

And if DRIVER_NAME doesn't get set, well, you just don't get the module
symlink in sysfs, just like what happens today if you don't provide that
field (but for PCI drivers, the .h file does it automatically for you.)

Anyway, this is a driver issue, NOT a module issue, so having to "plumb"
the module name all the way down through this really isn't the best
abstraction to do here from what I can tell.

thanks,

greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 02:45:14PM +0100, Greg KH wrote:
> On Wed, Dec 11, 2024 at 02:31:07PM +0100, Danilo Krummrich wrote:
> > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > 
> > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > in the register_driver call.
> > > > > > > > > 
> > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > "name" that is the issue here.
> > > > > > > > 
> > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > structure that has the name already embedded in it.
> > > > > > > 
> > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > but why it's using a different string other than the module name string
> > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > 
> > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > end.  Odds are something will break but who knows...
> > > > > > 
> > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > the module pointer will be NULL.)
> > > > > > 
> > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > 
> > > > > That's correct, and the reason why I pass through this name argument.
> > > > > 
> > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > 
> > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > just rely on the build system instead.
> > > > > > 
> > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > 
> > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > 
> > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > 
> > > > Actually, I now remember there was another reason why I pass it through in
> > > > `Module::init`.
> > > > 
> > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > 
> > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > from?
> > 
> > The problem is that register / unregister is encapsulated within methods of the
> > abstraction types. So the C macro trick (while generally possible) isn't
> > applicable.
> 
> Really?  You can't have something in a required "register()" type function?
> Something for when the driver "instance" is created as part of
> pci::Driver?  You do that today in your sample driver for the id table:
> 	const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
> 
> Something else called DRIVER_NAME that you could then set:
> 	const DRIVER_NAME: env!(KBUILD_MODNAME);

Sure, that's possible. But that means that the driver has to set it explicitly
-- even when e.g. module_pci_driver! is used.

In C you don't have that, because there it's implicit within the
pci_register_driver() macro. (Regardless of whether it's a single module for a
single driver or multiple drivers per module.)

Anyways, like I mentioned, given that we have `env!(KBUILD_MODNAME)` (which we
still need to add), there are other options to make it work similarly, e.g. add
a parameter to `pci::Adapter` and bake this into `module_pci_driver!`.

For this particular option, it would mean that for modules registering multiple
drivers a corresponding name would need to be passed explicitly.

> 
> Also, I think you will want this for when a single module registers
> multiple drivers which I think can happen at times, so you could
> manually override the DRIVER_NAME field.

My proposal above would provide this option, but do we care? In C no one ever
changes the name. There is zero users of __pci_register_driver(), everyone uses
pci_register_driver() where the name is just KBUILD_MODNAME. Same for
__platform_driver_register().

> 
> And if DRIVER_NAME doesn't get set, well, you just don't get the module
> symlink in sysfs, just like what happens today if you don't provide that
> field (but for PCI drivers, the .h file does it automatically for you.)
> 
> Anyway, this is a driver issue, NOT a module issue, so having to "plumb"
> the module name all the way down through this really isn't the best
> abstraction to do here from what I can tell.
> 
> thanks,
> 
> greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > the module name to `Module::init`.
> > > > > > > > >
> > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > in the register_driver call.
> > > > > > > > >
> > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > "name" that is the issue here.
> > > > > > > >
> > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > structure that has the name already embedded in it.
> > > > > > >
> > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > but why it's using a different string other than the module name string
> > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > >
> > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > end.  Odds are something will break but who knows...
> > > > > >
> > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > the module pointer will be NULL.)
> > > > > >
> > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > >
> > > > > That's correct, and the reason why I pass through this name argument.
> > > > >
> > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > >
> > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > just rely on the build system instead.
> > > > > >
> > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > >
> > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > >
> > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > >
> > > > Actually, I now remember there was another reason why I pass it through in
> > > > `Module::init`.
> > > >
> > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > >
> > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > from?
> >
> > The problem is that register / unregister is encapsulated within methods of the
> > abstraction types. So the C macro trick (while generally possible) isn't
> > applicable.
> >
> > I think we could avoid having an additional `name` parameter in `Module::init`,
> > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > passing it into the bus abstraction.
> >
> > However, similar to what Alice suggested in another thread, we could include
> > this step in the `module_*_driver!` macros.
> >
> > Modules that don't use this convenience macro would need to do it by hand
> > though. But that's probably not that big a deal.
> 
> I think we can do it in the core `module!` macro that everyone has to use.

How? The `module!` macro does not know about the registration instances within
the module structure.

> 
> Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Greg KH]

On Wed, Dec 11, 2024 at 03:21:53PM +0100, Danilo Krummrich wrote:
> > Really?  You can't have something in a required "register()" type function?
> > Something for when the driver "instance" is created as part of
> > pci::Driver?  You do that today in your sample driver for the id table:
> > 	const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
> > 
> > Something else called DRIVER_NAME that you could then set:
> > 	const DRIVER_NAME: env!(KBUILD_MODNAME);
> 
> Sure, that's possible. But that means that the driver has to set it explicitly
> -- even when e.g. module_pci_driver! is used.
> 
> In C you don't have that, because there it's implicit within the
> pci_register_driver() macro. (Regardless of whether it's a single module for a
> single driver or multiple drivers per module.)
> 
> Anyways, like I mentioned, given that we have `env!(KBUILD_MODNAME)` (which we
> still need to add), there are other options to make it work similarly, e.g. add
> a parameter to `pci::Adapter` and bake this into `module_pci_driver!`.

Ok, I'm all for that, just don't modify the module rust functions for it :)

> For this particular option, it would mean that for modules registering multiple
> drivers a corresponding name would need to be passed explicitly.

True.

> > Also, I think you will want this for when a single module registers
> > multiple drivers which I think can happen at times, so you could
> > manually override the DRIVER_NAME field.
> 
> My proposal above would provide this option, but do we care? In C no one ever
> changes the name. There is zero users of __pci_register_driver(), everyone uses
> pci_register_driver() where the name is just KBUILD_MODNAME. Same for
> __platform_driver_register().

You are right.  But I see other drivers messing with that field, oh no,
wait, that's just the EDAC layer doing really odd things (a known issue
as that layer does very many odd things.)

So nevermind, multiple drivers per module isn't going to be an issue, if
you all can move it to a macro (best yet, like what Alice pointed out),
that would be fine with me.

thanks,

greg k-h

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Alice Ryhl]

On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > >
> > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > >
> > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > in the register_driver call.
> > > > > > > > > >
> > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > "name" that is the issue here.
> > > > > > > > >
> > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > structure that has the name already embedded in it.
> > > > > > > >
> > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > >
> > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > end.  Odds are something will break but who knows...
> > > > > > >
> > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > the module pointer will be NULL.)
> > > > > > >
> > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > >
> > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > >
> > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > >
> > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > just rely on the build system instead.
> > > > > > >
> > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > >
> > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > >
> > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > >
> > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > `Module::init`.
> > > > >
> > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > >
> > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > from?
> > >
> > > The problem is that register / unregister is encapsulated within methods of the
> > > abstraction types. So the C macro trick (while generally possible) isn't
> > > applicable.
> > >
> > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > passing it into the bus abstraction.
> > >
> > > However, similar to what Alice suggested in another thread, we could include
> > > this step in the `module_*_driver!` macros.
> > >
> > > Modules that don't use this convenience macro would need to do it by hand
> > > though. But that's probably not that big a deal.
> >
> > I think we can do it in the core `module!` macro that everyone has to use.
>
> How? The `module!` macro does not know about the registration instances within
> the module structure.

You could have the module! macro emit something along these lines:

impl ModuleName for {type_} {
    const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
}

Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.

Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > >
> > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > >
> > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > in the register_driver call.
> > > > > > > > > > >
> > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > >
> > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > >
> > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > >
> > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > >
> > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > the module pointer will be NULL.)
> > > > > > > >
> > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > >
> > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > >
> > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > >
> > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > just rely on the build system instead.
> > > > > > > >
> > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > >
> > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > >
> > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > >
> > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > `Module::init`.
> > > > > >
> > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > >
> > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > from?
> > > >
> > > > The problem is that register / unregister is encapsulated within methods of the
> > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > applicable.
> > > >
> > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > passing it into the bus abstraction.
> > > >
> > > > However, similar to what Alice suggested in another thread, we could include
> > > > this step in the `module_*_driver!` macros.
> > > >
> > > > Modules that don't use this convenience macro would need to do it by hand
> > > > though. But that's probably not that big a deal.
> > >
> > > I think we can do it in the core `module!` macro that everyone has to use.
> >
> > How? The `module!` macro does not know about the registration instances within
> > the module structure.
> 
> You could have the module! macro emit something along these lines:
> 
> impl ModuleName for {type_} {
>     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> }
> 
> Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.

Where {type_} would need to be the driver's `Driver` structure?

We'd then need to define the bus adapter as:

`pub struct Adapter<T: Driver + ModuleName>(T)`

But the question stands I guess, how would the module macro know {type_}?

> 
> Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Alice Ryhl]

On Wed, Dec 11, 2024 at 3:52 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> > On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > >
> > > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > >
> > > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > > >
> > > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > > in the register_driver call.
> > > > > > > > > > > >
> > > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > > >
> > > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > > >
> > > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > > >
> > > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > > >
> > > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > > the module pointer will be NULL.)
> > > > > > > > >
> > > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > > >
> > > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > > >
> > > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > > >
> > > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > > just rely on the build system instead.
> > > > > > > > >
> > > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > > >
> > > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > > >
> > > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > > >
> > > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > > `Module::init`.
> > > > > > >
> > > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > > >
> > > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > > from?
> > > > >
> > > > > The problem is that register / unregister is encapsulated within methods of the
> > > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > > applicable.
> > > > >
> > > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > > passing it into the bus abstraction.
> > > > >
> > > > > However, similar to what Alice suggested in another thread, we could include
> > > > > this step in the `module_*_driver!` macros.
> > > > >
> > > > > Modules that don't use this convenience macro would need to do it by hand
> > > > > though. But that's probably not that big a deal.
> > > >
> > > > I think we can do it in the core `module!` macro that everyone has to use.
> > >
> > > How? The `module!` macro does not know about the registration instances within
> > > the module structure.
> >
> > You could have the module! macro emit something along these lines:
> >
> > impl ModuleName for {type_} {
> >     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> > }
> >
> > Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.
>
> Where {type_} would need to be the driver's `Driver` structure?
>
> We'd then need to define the bus adapter as:
>
> `pub struct Adapter<T: Driver + ModuleName>(T)`
>
> But the question stands I guess, how would the module macro know {type_}?

If you look at the macro implementation in rust/macros/module.rs you
will find many uses of {type_} throughout the expansion. It's whatever
is passed to the macro using the `type:` argument.


Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 03:55:47PM +0100, Alice Ryhl wrote:
> On Wed, Dec 11, 2024 at 3:52 PM Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> > > On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > >
> > > > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > >
> > > > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > > > in the register_driver call.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > > > >
> > > > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > > > >
> > > > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > > > >
> > > > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > > > >
> > > > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > > > the module pointer will be NULL.)
> > > > > > > > > >
> > > > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > > > >
> > > > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > > > >
> > > > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > > > >
> > > > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > > > just rely on the build system instead.
> > > > > > > > > >
> > > > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > > > >
> > > > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > > > >
> > > > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > > > >
> > > > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > > > `Module::init`.
> > > > > > > >
> > > > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > > > >
> > > > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > > > from?
> > > > > >
> > > > > > The problem is that register / unregister is encapsulated within methods of the
> > > > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > > > applicable.
> > > > > >
> > > > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > > > passing it into the bus abstraction.
> > > > > >
> > > > > > However, similar to what Alice suggested in another thread, we could include
> > > > > > this step in the `module_*_driver!` macros.
> > > > > >
> > > > > > Modules that don't use this convenience macro would need to do it by hand
> > > > > > though. But that's probably not that big a deal.
> > > > >
> > > > > I think we can do it in the core `module!` macro that everyone has to use.
> > > >
> > > > How? The `module!` macro does not know about the registration instances within
> > > > the module structure.
> > >
> > > You could have the module! macro emit something along these lines:
> > >
> > > impl ModuleName for {type_} {
> > >     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> > > }
> > >
> > > Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.
> >
> > Where {type_} would need to be the driver's `Driver` structure?
> >
> > We'd then need to define the bus adapter as:
> >
> > `pub struct Adapter<T: Driver + ModuleName>(T)`
> >
> > But the question stands I guess, how would the module macro know {type_}?
> 
> If you look at the macro implementation in rust/macros/module.rs you
> will find many uses of {type_} throughout the expansion. It's whatever
> is passed to the macro using the `type:` argument.

Oh, I see. So, this means that module / driver author would still need to create
the "connection" by listing the correspong driver types in the module! macro,
right?

If so, I think it'd be better to do it in the `module_*_driver!` macro and let
people implement the trait by hand for modules with multiple drivers (which
should be pretty rare).

The reason is that I think that otherwise we're probably encoding too much
semantics into the `module!` macro that isn't obvious and people need to
understand.

> 
> 
> Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Alice Ryhl]

On Wed, Dec 11, 2024 at 4:03 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> On Wed, Dec 11, 2024 at 03:55:47PM +0100, Alice Ryhl wrote:
> > On Wed, Dec 11, 2024 at 3:52 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > >
> > > On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> > > > On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > >
> > > > > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > > > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > > >
> > > > > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > > > > in the register_driver call.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > > > > >
> > > > > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > > > > >
> > > > > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > > > > >
> > > > > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > > > > the module pointer will be NULL.)
> > > > > > > > > > >
> > > > > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > > > > >
> > > > > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > > > > >
> > > > > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > > > > >
> > > > > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > > > > just rely on the build system instead.
> > > > > > > > > > >
> > > > > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > > > > >
> > > > > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > > > > >
> > > > > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > > > > >
> > > > > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > > > > `Module::init`.
> > > > > > > > >
> > > > > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > > > > >
> > > > > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > > > > from?
> > > > > > >
> > > > > > > The problem is that register / unregister is encapsulated within methods of the
> > > > > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > > > > applicable.
> > > > > > >
> > > > > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > > > > passing it into the bus abstraction.
> > > > > > >
> > > > > > > However, similar to what Alice suggested in another thread, we could include
> > > > > > > this step in the `module_*_driver!` macros.
> > > > > > >
> > > > > > > Modules that don't use this convenience macro would need to do it by hand
> > > > > > > though. But that's probably not that big a deal.
> > > > > >
> > > > > > I think we can do it in the core `module!` macro that everyone has to use.
> > > > >
> > > > > How? The `module!` macro does not know about the registration instances within
> > > > > the module structure.
> > > >
> > > > You could have the module! macro emit something along these lines:
> > > >
> > > > impl ModuleName for {type_} {
> > > >     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> > > > }
> > > >
> > > > Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.
> > >
> > > Where {type_} would need to be the driver's `Driver` structure?
> > >
> > > We'd then need to define the bus adapter as:
> > >
> > > `pub struct Adapter<T: Driver + ModuleName>(T)`
> > >
> > > But the question stands I guess, how would the module macro know {type_}?
> >
> > If you look at the macro implementation in rust/macros/module.rs you
> > will find many uses of {type_} throughout the expansion. It's whatever
> > is passed to the macro using the `type:` argument.
>
> Oh, I see. So, this means that module / driver author would still need to create
> the "connection" by listing the correspong driver types in the module! macro,
> right?

I'm not sure what you mean. I'm *not* suggesting any changes to the
interface of module! or module_*_driver!.

> If so, I think it'd be better to do it in the `module_*_driver!` macro and let
> people implement the trait by hand for modules with multiple drivers (which
> should be pretty rare).
>
> The reason is that I think that otherwise we're probably encoding too much
> semantics into the `module!` macro that isn't obvious and people need to
> understand.
>
> >
> >
> > Alice

Re: [PATCH v5 14/16] rust: platform: add basic platform device / driver abstractions

[Rob Herring]

On Tue, Dec 10, 2024 at 11:46:41PM +0100, Danilo Krummrich wrote:
> Implement the basic platform bus abstractions required to write a basic
> platform driver. This includes the following data structures:
> 
> The `platform::Driver` trait represents the interface to the driver and
> provides `platform::Driver::probe` for the driver to implement.
> 
> The `platform::Device` abstraction represents a `struct platform_device`.
> 
> In order to provide the platform bus specific parts to a generic
> `driver::Registration` the `driver::RegistrationOps` trait is implemented
> by `platform::Adapter`.
> 
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  MAINTAINERS                     |   1 +
>  rust/bindings/bindings_helper.h |   2 +
>  rust/helpers/helpers.c          |   1 +
>  rust/helpers/platform.c         |  13 +++
>  rust/kernel/lib.rs              |   1 +
>  rust/kernel/platform.rs         | 193 ++++++++++++++++++++++++++++++++
>  6 files changed, 211 insertions(+)
>  create mode 100644 rust/helpers/platform.c
>  create mode 100644 rust/kernel/platform.rs

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH v5 15/16] samples: rust: add Rust platform sample driver

[Rob Herring]

On Tue, Dec 10, 2024 at 11:46:42PM +0100, Danilo Krummrich wrote:
> Add a sample Rust platform driver illustrating the usage of the platform
> bus abstractions.
> 
> This driver probes through either a match of device / driver name or a
> match within the OF ID table.
> 
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  MAINTAINERS                                  |  1 +
>  drivers/of/unittest-data/tests-platform.dtsi |  5 ++
>  samples/rust/Kconfig                         | 10 ++++
>  samples/rust/Makefile                        |  1 +
>  samples/rust/rust_driver_platform.rs         | 49 ++++++++++++++++++++
>  5 files changed, 66 insertions(+)
>  create mode 100644 samples/rust/rust_driver_platform.rs

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 04:15:19PM +0100, Alice Ryhl wrote:
> On Wed, Dec 11, 2024 at 4:03 PM Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > On Wed, Dec 11, 2024 at 03:55:47PM +0100, Alice Ryhl wrote:
> > > On Wed, Dec 11, 2024 at 3:52 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > >
> > > > On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> > > > > On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > >
> > > > > > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > > > > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > > > >
> > > > > > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > > > > > in the register_driver call.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > > > > > >
> > > > > > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > > > > > >
> > > > > > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > > > > > >
> > > > > > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > > > > > the module pointer will be NULL.)
> > > > > > > > > > > >
> > > > > > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > > > > > >
> > > > > > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > > > > > >
> > > > > > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > > > > > >
> > > > > > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > > > > > just rely on the build system instead.
> > > > > > > > > > > >
> > > > > > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > > > > > >
> > > > > > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > > > > > >
> > > > > > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > > > > > >
> > > > > > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > > > > > `Module::init`.
> > > > > > > > > >
> > > > > > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > > > > > >
> > > > > > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > > > > > from?
> > > > > > > >
> > > > > > > > The problem is that register / unregister is encapsulated within methods of the
> > > > > > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > > > > > applicable.
> > > > > > > >
> > > > > > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > > > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > > > > > passing it into the bus abstraction.
> > > > > > > >
> > > > > > > > However, similar to what Alice suggested in another thread, we could include
> > > > > > > > this step in the `module_*_driver!` macros.
> > > > > > > >
> > > > > > > > Modules that don't use this convenience macro would need to do it by hand
> > > > > > > > though. But that's probably not that big a deal.
> > > > > > >
> > > > > > > I think we can do it in the core `module!` macro that everyone has to use.
> > > > > >
> > > > > > How? The `module!` macro does not know about the registration instances within
> > > > > > the module structure.
> > > > >
> > > > > You could have the module! macro emit something along these lines:
> > > > >
> > > > > impl ModuleName for {type_} {
> > > > >     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> > > > > }
> > > > >
> > > > > Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.
> > > >
> > > > Where {type_} would need to be the driver's `Driver` structure?
> > > >
> > > > We'd then need to define the bus adapter as:
> > > >
> > > > `pub struct Adapter<T: Driver + ModuleName>(T)`
> > > >
> > > > But the question stands I guess, how would the module macro know {type_}?
> > >
> > > If you look at the macro implementation in rust/macros/module.rs you
> > > will find many uses of {type_} throughout the expansion. It's whatever
> > > is passed to the macro using the `type:` argument.
> >
> > Oh, I see. So, this means that module / driver author would still need to create
> > the "connection" by listing the correspong driver types in the module! macro,
> > right?
> 
> I'm not sure what you mean. I'm *not* suggesting any changes to the
> interface of module! or module_*_driver!.

Huh! Seems like we're talking past each other than. Maybe we can briefly
discuss it in today's call?

> 
> > If so, I think it'd be better to do it in the `module_*_driver!` macro and let
> > people implement the trait by hand for modules with multiple drivers (which
> > should be pretty rare).
> >
> > The reason is that I think that otherwise we're probably encoding too much
> > semantics into the `module!` macro that isn't obvious and people need to
> > understand.
> >
> > >
> > >
> > > Alice

Re: [PATCH v5 01/16] rust: pass module name to `Module::init`

[Danilo Krummrich]

On Wed, Dec 11, 2024 at 04:36:35PM +0100, Danilo Krummrich wrote:
> On Wed, Dec 11, 2024 at 04:15:19PM +0100, Alice Ryhl wrote:
> > On Wed, Dec 11, 2024 at 4:03 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > >
> > > On Wed, Dec 11, 2024 at 03:55:47PM +0100, Alice Ryhl wrote:
> > > > On Wed, Dec 11, 2024 at 3:52 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > >
> > > > > On Wed, Dec 11, 2024 at 03:45:53PM +0100, Alice Ryhl wrote:
> > > > > > On Wed, Dec 11, 2024 at 3:29 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > > >
> > > > > > > On Wed, Dec 11, 2024 at 02:34:54PM +0100, Alice Ryhl wrote:
> > > > > > > > On Wed, Dec 11, 2024 at 2:31 PM Danilo Krummrich <dakr@kernel.org> wrote:
> > > > > > > > >
> > > > > > > > > On Wed, Dec 11, 2024 at 02:14:37PM +0100, Greg KH wrote:
> > > > > > > > > > On Wed, Dec 11, 2024 at 01:34:31PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > On Wed, Dec 11, 2024 at 01:22:33PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > On Wed, Dec 11, 2024 at 12:05:10PM +0100, Greg KH wrote:
> > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:59:54AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:48:23AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > > On Wed, Dec 11, 2024 at 11:45:20AM +0100, Greg KH wrote:
> > > > > > > > > > > > > > > > On Tue, Dec 10, 2024 at 11:46:28PM +0100, Danilo Krummrich wrote:
> > > > > > > > > > > > > > > > > In a subsequent patch we introduce the `Registration` abstraction used
> > > > > > > > > > > > > > > > > to register driver structures. Some subsystems require the module name on
> > > > > > > > > > > > > > > > > driver registration (e.g. PCI in __pci_register_driver()), hence pass
> > > > > > > > > > > > > > > > > the module name to `Module::init`.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Nit, we don't need the NAME of the PCI driver (well, we do like it, but
> > > > > > > > > > > > > > > > that's not the real thing), we want the pointer to the module structure
> > > > > > > > > > > > > > > > in the register_driver call.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Does this provide for that?  I'm thinking it does, but it's not the
> > > > > > > > > > > > > > > > "name" that is the issue here.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Wait, no, you really do want the name, don't you.  You refer to
> > > > > > > > > > > > > > > "module.0" to get the module structure pointer (if I'm reading the code
> > > > > > > > > > > > > > > right), but as you have that pointer already, why can't you just use
> > > > > > > > > > > > > > > module->name there as well as you have a pointer to a valid module
> > > > > > > > > > > > > > > structure that has the name already embedded in it.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > In digging further, it's used by the pci code to call into lower layers,
> > > > > > > > > > > > > > but why it's using a different string other than the module name string
> > > > > > > > > > > > > > is beyond me.  Looks like this goes way back before git was around, and
> > > > > > > > > > > > > > odds are it's my fault for something I wrote a long time ago.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I'll see if I can just change the driver core to not need a name at all,
> > > > > > > > > > > > > > and pull it from the module which would make all of this go away in the
> > > > > > > > > > > > > > end.  Odds are something will break but who knows...
> > > > > > > > > > > > >
> > > > > > > > > > > > > Nope, things break, the "name" is there to handle built-in modules (as
> > > > > > > > > > > > > the module pointer will be NULL.)
> > > > > > > > > > > > >
> > > > > > > > > > > > > So what you really want is not the module->name (as I don't think that
> > > > > > > > > > > > > will be set), but you want KBUILD_MODNAME which the build system sets.
> > > > > > > > > > > >
> > > > > > > > > > > > That's correct, and the reason why I pass through this name argument.
> > > > > > > > > > > >
> > > > > > > > > > > > Sorry I wasn't able to reply earlier to save you some time.
> > > > > > > > > > > >
> > > > > > > > > > > > > You shouldn't need to pass the name through all of the subsystems here,
> > > > > > > > > > > > > just rely on the build system instead.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Or does the Rust side not have KBUILD_MODNAME?
> > > > > > > > > > > >
> > > > > > > > > > > > AFAIK, it doesn't (or didn't have at the time I wrote the patch).
> > > > > > > > > > > >
> > > > > > > > > > > > @Miguel: Can we access KBUILD_MODNAME conveniently?
> > > > > > > > > > >
> > > > > > > > > > > Actually, I now remember there was another reason why I pass it through in
> > > > > > > > > > > `Module::init`.
> > > > > > > > > > >
> > > > > > > > > > > Even if we had env!(KBUILD_MODNAME) already, I'd want to use it from the bus
> > > > > > > > > > > abstraction code, e.g. rust/kernel/pci.rs. But since this is generic code, it
> > > > > > > > > > > won't get the KBUILD_MODNAME from the module that is using the bus abstraction.
> > > > > > > > > >
> > > > > > > > > > Rust can't do that in a macro somehow that all pci rust drivers can pull
> > > > > > > > > > from?
> > > > > > > > >
> > > > > > > > > The problem is that register / unregister is encapsulated within methods of the
> > > > > > > > > abstraction types. So the C macro trick (while generally possible) isn't
> > > > > > > > > applicable.
> > > > > > > > >
> > > > > > > > > I think we could avoid having an additional `name` parameter in `Module::init`,
> > > > > > > > > but it would still need to be the driver resolving `env!(KBUILD_MODNAME)`
> > > > > > > > > passing it into the bus abstraction.
> > > > > > > > >
> > > > > > > > > However, similar to what Alice suggested in another thread, we could include
> > > > > > > > > this step in the `module_*_driver!` macros.
> > > > > > > > >
> > > > > > > > > Modules that don't use this convenience macro would need to do it by hand
> > > > > > > > > though. But that's probably not that big a deal.
> > > > > > > >
> > > > > > > > I think we can do it in the core `module!` macro that everyone has to use.
> > > > > > >
> > > > > > > How? The `module!` macro does not know about the registration instances within
> > > > > > > the module structure.
> > > > > >
> > > > > > You could have the module! macro emit something along these lines:
> > > > > >
> > > > > > impl ModuleName for {type_} {
> > > > > >     const NAME: &'static CStr = c_str!(env!("KBUILD_MODNAME"));
> > > > > > }
> > > > > >
> > > > > > Then you can do `<Self as ModuleName>::NAME` to obtain the name elsewhere.
> > > > >
> > > > > Where {type_} would need to be the driver's `Driver` structure?
> > > > >
> > > > > We'd then need to define the bus adapter as:
> > > > >
> > > > > `pub struct Adapter<T: Driver + ModuleName>(T)`
> > > > >
> > > > > But the question stands I guess, how would the module macro know {type_}?
> > > >
> > > > If you look at the macro implementation in rust/macros/module.rs you
> > > > will find many uses of {type_} throughout the expansion. It's whatever
> > > > is passed to the macro using the `type:` argument.
> > >
> > > Oh, I see. So, this means that module / driver author would still need to create
> > > the "connection" by listing the correspong driver types in the module! macro,
> > > right?
> > 
> > I'm not sure what you mean. I'm *not* suggesting any changes to the
> > interface of module! or module_*_driver!.
> 
> Huh! Seems like we're talking past each other than. Maybe we can briefly
> discuss it in today's call?

I think I figured out the confusion.

The {type_} in the module macro is the thing that implements the `Module` or
`InPlaceModule` trait. However, that's *not* the driver type that is embedded in
the bus adapter.

For instance, what we have is:

```
struct MyDriver;

struct MyModule {
   _driver: Registration<pci::Adapter<MyDriver>,
};

impl pci::Driver for MyDriver { ... }

impl InPlaceModule for MyModule { ... }

module! {
   type: MyModule,
   ...
}
```

This means `module!` would generate:

`impl ModuleName for MyModule { ... }`

But this doesn't help, because `pci::Adapter` doesn't know about `MyModule`, but
only about `MyDriver`.

Do I miss anything?

> 
> > 
> > > If so, I think it'd be better to do it in the `module_*_driver!` macro and let
> > > people implement the trait by hand for modules with multiple drivers (which
> > > should be pretty rare).
> > >
> > > The reason is that I think that otherwise we're probably encoding too much
> > > semantics into the `module!` macro that isn't obvious and people need to
> > > understand.
> > >
> > > >
> > > >
> > > > Alice

Re: [PATCH v5 04/16] rust: add rcu abstraction

[Boqun Feng]

Hi Danilo,

This looks good so far, could you please Cc RCU maintainers for the next
version (if there is one).

A few nits below, with or without, feel free to add:

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

On Tue, Dec 10, 2024 at 11:46:31PM +0100, Danilo Krummrich wrote:
> From: Wedson Almeida Filho <wedsonaf@gmail.com>
> 
> Add a simple abstraction to guard critical code sections with an rcu
> read lock.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Co-developed-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/helpers/helpers.c  |  1 +
>  rust/helpers/rcu.c      | 13 ++++++++++++
>  rust/kernel/sync.rs     |  1 +
>  rust/kernel/sync/rcu.rs | 47 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 62 insertions(+)
>  create mode 100644 rust/helpers/rcu.c
>  create mode 100644 rust/kernel/sync/rcu.rs
> 
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index dcf827a61b52..060750af6524 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -20,6 +20,7 @@
>  #include "page.c"
>  #include "pid_namespace.c"
>  #include "rbtree.c"
> +#include "rcu.c"
>  #include "refcount.c"
>  #include "security.c"
>  #include "signal.c"
> diff --git a/rust/helpers/rcu.c b/rust/helpers/rcu.c
> new file mode 100644
> index 000000000000..f1cec6583513
> --- /dev/null
> +++ b/rust/helpers/rcu.c
> @@ -0,0 +1,13 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/rcupdate.h>
> +
> +void rust_helper_rcu_read_lock(void)
> +{
> +	rcu_read_lock();
> +}
> +
> +void rust_helper_rcu_read_unlock(void)
> +{
> +	rcu_read_unlock();
> +}
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 1eab7ebf25fd..0654008198b2 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -12,6 +12,7 @@
>  pub mod lock;
>  mod locked_by;
>  pub mod poll;
> +pub mod rcu;
>  
>  pub use arc::{Arc, ArcBorrow, UniqueArc};
>  pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
> diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs
> new file mode 100644
> index 000000000000..3beef70d5f34
> --- /dev/null
> +++ b/rust/kernel/sync/rcu.rs
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! RCU support.
> +//!
> +//! C header: [`include/linux/rcupdate.h`](srctree/include/linux/rcupdate.h)
> +
> +use crate::{bindings, types::NotThreadSafe};
> +
> +/// Evidence that the RCU read side lock is held on the current thread/CPU.
> +///
> +/// The type is explicitly not `Send` because this property is per-thread/CPU.
> +///
> +/// # Invariants
> +///
> +/// The RCU read side lock is actually held while instances of this guard exist.
> +pub struct Guard(NotThreadSafe);
> +
> +impl Guard {
> +    /// Acquires the RCU read side lock and returns a guard.
> +    pub fn new() -> Self {
> +        // SAFETY: An FFI call with no additional requirements.
> +        unsafe { bindings::rcu_read_lock() };
> +        // INVARIANT: The RCU read side lock was just acquired above.
> +        Self(NotThreadSafe)
> +    }
> +
> +    /// Explicitly releases the RCU read side lock.
> +    pub fn unlock(self) {}
> +}
> +
> +impl Default for Guard {
> +    fn default() -> Self {
> +        Self::new()
> +    }
> +}
> +
> +impl Drop for Guard {
> +    fn drop(&mut self) {
> +        // SAFETY: By the type invariants, the rcu read side is locked, so it is ok to unlock it.

s/rcu/RCU

when referring the RCU mechanism or the subsystem, it makes sense to use
the capitalized abbreviation.

Regards,
Boqun

> +        unsafe { bindings::rcu_read_unlock() };
> +    }
> +}
> +
> +/// Acquires the RCU read side lock.
> +pub fn read_lock() -> Guard {
> +    Guard::new()
> +}
> -- 
> 2.47.0
> 

Re: [PATCH v5 13/16] rust: driver: implement `Adapter`

[Fabien Parent]

Hi Danilo,

On Tue, Dec 10, 2024 at 2:51 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> In order to not duplicate code in bus specific implementations (e.g.
> platform), implement a generic `driver::Adapter` to represent the
> connection of matched drivers and devices.
>
> Bus specific `Adapter` implementations can simply implement this trait
> to inherit generic functionality, such as matching OF or ACPI device IDs
> and ID table entries.
>
> Suggested-by: Rob Herring (Arm) <robh@kernel.org>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/driver.rs | 59 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
> index ab0bb46fe2cc..d169899a5da1 100644
> --- a/rust/kernel/driver.rs
> +++ b/rust/kernel/driver.rs
> @@ -6,7 +6,9 @@
>  //! register using the [`Registration`] class.
>
>  use crate::error::{Error, Result};
> -use crate::{init::PinInit, str::CStr, try_pin_init, types::Opaque, ThisModule};
> +use crate::{
> +    device, device_id, init::PinInit, of, str::CStr, try_pin_init, types::Opaque, ThisModule,
> +};
>  use core::pin::Pin;
>  use macros::{pin_data, pinned_drop};
>
> @@ -114,3 +116,58 @@ macro_rules! module_driver {
>          }
>      }
>  }
> +
> +/// The bus independent adapter to match a drivers and a devices.
> +///
> +/// This trait should be implemented by the bus specific adapter, which represents the connection
> +/// of a device and a driver.
> +///
> +/// It provides bus independent functions for device / driver interactions.
> +pub trait Adapter {
> +    /// The type holding driver private data about each device id supported by the driver.
> +    type IdInfo: 'static;
> +
> +    /// The [`of::IdTable`] of the corresponding driver.
> +    fn of_id_table() -> of::IdTable<Self::IdInfo>;

I think we may want this to return an Option<of::IdTable<Self::IdInfo>>
instead. I don't think we want to force every bus abstraction to have
to implement every possible IdTable that this adapter will support.

For instance if your driver only supports ACPI, it will still be required
to provide an empty OF table because the bus abstraction needs it
for implementing this trait.

> +
> +    /// Returns the driver's private data from the matching entry in the [`of::IdTable`], if any.
> +    ///
> +    /// If this returns `None`, it means there is no match with an entry in the [`of::IdTable`].
> +    #[cfg(CONFIG_OF)]
> +    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
> +        let table = Self::of_id_table();
> +
> +        // SAFETY:
> +        // - `table` has static lifetime, hence it's valid for read,
> +        // - `dev` is guaranteed to be valid while it's alive, and so is `pdev.as_ref().as_raw()`.
> +        let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
> +
> +        if raw_id.is_null() {
> +            None
> +        } else {
> +            // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and
> +            // does not add additional invariants, so it's safe to transmute.
> +            let id = unsafe { &*raw_id.cast::<of::DeviceId>() };
> +
> +            Some(table.info(<of::DeviceId as device_id::RawDeviceId>::index(id)))
> +        }
> +    }
> +
> +    #[cfg(not(CONFIG_OF))]
> +    fn of_id_info(_dev: &device::Device) -> Option<&'static Self::IdInfo> {
> +        None
> +    }
> +
> +    /// Returns the driver's private data from the matching entry of any of the ID tables, if any.
> +    ///
> +    /// If this returns `None`, it means that there is no match in any of the ID tables directly
> +    /// associated with a [`device::Device`].
> +    fn id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
> +        let id = Self::of_id_info(dev);
> +        if id.is_some() {
> +            return id;
> +        }
> +
> +        None
> +    }
> +}
> --
> 2.47.0
>