* [PATCH 1/2] rust: drm: Introduce DeviceCtx
2025-11-07 19:23 [PATCH 0/2] rust: drm: Introduce DeviceCtx Lyude Paul
@ 2025-11-07 19:23 ` Lyude Paul
2025-11-07 19:23 ` [PATCH 2/2] rust/drm/gem: Use DeviceCtx with GEM objects Lyude Paul
1 sibling, 0 replies; 3+ messages in thread
From: Lyude Paul @ 2025-11-07 19:23 UTC (permalink / raw)
To: linux-kernel, rust-for-linux, dri-devel
Cc: Danilo Krummrich, Alice Ryhl, David Airlie, Simona Vetter,
Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Miguel Ojeda,
Alex Gaynor, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Trevor Gross,
open list:DRM DRIVER FOR NVIDIA GPUS [RUST]
One of the tricky things about DRM bindings in Rust is the fact that
initialization of a DRM device is a multi-step process. It's quite normal
for a device driver to start making use of its DRM device for tasks like
creating GEM objects before userspace registration happens. This is an
issue in rust though, since prior to userspace registration the device is
only partly initialized. This means there's a plethora of DRM device
operations we can't yet expose without opening up the door to UB if the DRM
device in question isn't yet registered.
Additionally, this isn't something we can reliably check at runtime. And
even if we could, performing an operation which requires the device be
registered when the device isn't actually registered is a programmer bug,
meaning there's no real way to gracefully handle such a mistake at runtime.
And even if that wasn't the case, it would be horrendously annoying and
noisy to have to check if a device is registered constantly throughout a
driver.
In order to solve this, we first take inspiration from
`kernel::device::DeviceCtx` and introduce `kernel::drm::DeviceCtx`.
This provides us with a ZST type that we can generalize over to represent
contexts where a device is known to have been registered with userspace at
some point in time (`Registered`), along with contexts where we can't make
such a guarantee (`AnyCtx`).
It's important to note we intentionally do not provide a `DeviceCtx`
which represents an unregistered device. This is because there's no
reasonable way to guarantee that a device with long-living references to
itself will not be registered eventually with userspace. Instead, we
provide a new-type for this: `UnregisteredDevice` which can
provide a guarantee that the `Device` has never been registered with
userspace. To ensure this, we modify `Registration` so that creating a new
`Registration` requires passing ownership of an `UnregisteredDevice`.
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
drivers/gpu/drm/nova/driver.rs | 8 +-
drivers/gpu/drm/tyr/driver.rs | 13 ++-
rust/kernel/drm/device.rs | 167 +++++++++++++++++++++++++++------
rust/kernel/drm/driver.rs | 35 +++++--
rust/kernel/drm/mod.rs | 4 +
5 files changed, 181 insertions(+), 46 deletions(-)
diff --git a/drivers/gpu/drm/nova/driver.rs b/drivers/gpu/drm/nova/driver.rs
index 91b7380f83ab4..c78d69d5f045a 100644
--- a/drivers/gpu/drm/nova/driver.rs
+++ b/drivers/gpu/drm/nova/driver.rs
@@ -13,7 +13,7 @@ pub(crate) struct NovaDriver {
}
/// Convienence type alias for the DRM device type for this driver
-pub(crate) type NovaDevice = drm::Device<NovaDriver>;
+pub(crate) type NovaDevice<Ctx = drm::Registered> = drm::Device<NovaDriver, Ctx>;
#[pin_data]
pub(crate) struct NovaData {
@@ -48,10 +48,10 @@ impl auxiliary::Driver for NovaDriver {
fn probe(adev: &auxiliary::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
let data = try_pin_init!(NovaData { adev: adev.into() });
- let drm = drm::Device::<Self>::new(adev.as_ref(), data)?;
- drm::Registration::new_foreign_owned(&drm, adev.as_ref(), 0)?;
+ let drm = drm::UnregisteredDevice::<Self>::new(adev.as_ref(), data)?;
+ let drm = drm::Registration::new_foreign_owned(drm, adev.as_ref(), 0)?;
- Ok(KBox::new(Self { drm }, GFP_KERNEL)?.into())
+ Ok(KBox::new(Self { drm: drm.into() }, GFP_KERNEL)?.into())
}
}
diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index d5625dd1e41c8..e3ea5ad85f49b 100644
--- a/drivers/gpu/drm/tyr/driver.rs
+++ b/drivers/gpu/drm/tyr/driver.rs
@@ -30,7 +30,7 @@
pub(crate) type IoMem = kernel::io::mem::IoMem<SZ_2M>;
/// Convenience type alias for the DRM device type for this driver.
-pub(crate) type TyrDevice = drm::Device<TyrDriver>;
+pub(crate) type TyrDevice<Ctx = drm::Registered> = drm::Device<TyrDriver, Ctx>;
#[pin_data(PinnedDrop)]
pub(crate) struct TyrDriver {
@@ -140,10 +140,15 @@ fn probe(
gpu_info,
});
- let tdev: ARef<TyrDevice> = drm::Device::new(pdev.as_ref(), data)?;
- drm::driver::Registration::new_foreign_owned(&tdev, pdev.as_ref(), 0)?;
+ let tdev = drm::UnregisteredDevice::<Self>::new(pdev.as_ref(), data)?;
+ let tdev = drm::driver::Registration::new_foreign_owned(tdev, pdev.as_ref(), 0)?;
- let driver = KBox::pin_init(try_pin_init!(TyrDriver { device: tdev }), GFP_KERNEL)?;
+ let driver = KBox::pin_init(
+ try_pin_init!(TyrDriver {
+ device: tdev.into()
+ }),
+ GFP_KERNEL,
+ )?;
// We need this to be dev_info!() because dev_dbg!() does not work at
// all in Rust for now, and we need to see whether probe succeeded.
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 3ce8f62a00569..00072984930a3 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -7,14 +7,14 @@
use crate::{
alloc::allocator::Kmalloc,
bindings, device, drm,
- drm::driver::AllocImpl,
+ drm::{driver::AllocImpl, private::Sealed},
error::from_err_ptr,
error::Result,
prelude::*,
sync::aref::{ARef, AlwaysRefCounted},
types::Opaque,
};
-use core::{alloc::Layout, mem, ops::Deref, ptr, ptr::NonNull};
+use core::{alloc::Layout, marker::PhantomData, mem, ops::Deref, ptr, ptr::NonNull};
#[cfg(CONFIG_DRM_LEGACY)]
macro_rules! drm_legacy_fields {
@@ -47,26 +47,83 @@ macro_rules! drm_legacy_fields {
}
}
-/// A typed DRM device with a specific `drm::Driver` implementation.
+macro_rules! drm_dev_ctx {
+ (
+ $( #[$attrs:meta] )*
+ $name:ident
+ ) => {
+ $( #[$attrs] )*
+ pub struct $name;
+
+ impl DeviceCtx for $name {}
+ impl Sealed for $name {}
+
+ // SAFETY: All registration states are free of side-effects (e.g. no Drop) and are ZSTs,
+ // thus they are always thread-safe.
+ unsafe impl Send for $name {}
+ // SAFETY: All registration states are free of side-effects (e.g. no Drop) and are ZSTs,
+ // thus they are always thread-safe.
+ unsafe impl Sync for $name {}
+ };
+}
+
+/// A trait implemented by all possible contexts a [`Device`] can be used in.
+pub trait DeviceCtx: Sealed + Send + Sync {}
+
+drm_dev_ctx! {
+ /// The [`DeviceCtx`] of a [`Device`] that was registered with userspace at some point.
+ ///
+ /// This represents a [`Device`] which is guaranteed to have been registered with userspace at
+ /// some point in time. Once a DRM device has registered itself with userspace, it is safe to
+ /// assume that the initialization process for the DRM device has completed.
+ ///
+ /// Note: A device in this context is not guaranteed to remain registered with userspace for its
+ /// entire lifetime, as this is impossible to guarantee at compile-time. However, any
+ /// userspace-dependent operations performed with an unregistered device in this [`DeviceCtx`]
+ /// are guaranteed to be no-ops.
+ ///
+ /// # Invariants
+ ///
+ /// A [`Device`] in this [`DeviceCtx`] is guaranteed to have called `drm_dev_register` once.
+ Registered
+}
+
+drm_dev_ctx! {
+ /// The [`DeviceCtx`] of a [`Device`] that has no initialization or registration guarantees.
+ ///
+ /// A [`Device`] in this context could be in any state, pre or post registration, and is only
+ /// guaranteed to be minimally initialized. As such the operations which may be performed on
+ /// such [`Device`]s are more limited then in the [`Registered`] context.
+ AnyCtx
+}
+
+/// A [`Device`] which is known at compile-time to be unregistered with userspace.
///
-/// The device is always reference-counted.
+/// This type allows performing operations which are only safe to do before userspace registration,
+/// and can be used to create a [`Registration`](drm::driver::Registration) once the driver is ready
+/// to register the device with userspace.
///
/// # Invariants
///
-/// `self.dev` is a valid instance of a `struct device`.
-#[repr(C)]
-pub struct Device<T: drm::Driver> {
- dev: Opaque<bindings::drm_device>,
- data: T::Data,
+/// The device in `self.0` is guaranteed to be a newly created [`Device`] that has not yet been
+/// registered with userspace until this type is dropped.
+pub struct UnregisteredDevice<T: drm::Driver>(ARef<Device<T, AnyCtx>>);
+
+impl<T: drm::Driver> Deref for UnregisteredDevice<T> {
+ type Target = Device<T, AnyCtx>;
+
+ fn deref(&self) -> &Self::Target {
+ &self.0
+ }
}
-impl<T: drm::Driver> Device<T> {
+impl<T: drm::Driver> UnregisteredDevice<T> {
const VTABLE: bindings::drm_driver = drm_legacy_fields! {
load: None,
open: Some(drm::File::<T::File>::open_callback),
postclose: Some(drm::File::<T::File>::postclose_callback),
unload: None,
- release: Some(Self::release),
+ release: Some(Device::<T>::release),
master_set: None,
master_drop: None,
debugfs_init: None,
@@ -94,8 +151,10 @@ impl<T: drm::Driver> Device<T> {
const GEM_FOPS: bindings::file_operations = drm::gem::create_fops();
- /// Create a new `drm::Device` for a `drm::Driver`.
- pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<ARef<Self>> {
+ /// Create a new `UnregisteredDevice` for a `drm::Driver`.
+ ///
+ /// This can be used to create a [`Registration`](kernel::drm::Registration).
+ pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<Self> {
// `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
// compatible `Layout`.
let layout = Kmalloc::aligned_layout(Layout::new::<Self>());
@@ -103,12 +162,12 @@ pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<A
// SAFETY:
// - `VTABLE`, as a `const` is pinned to the read-only section of the compilation,
// - `dev` is valid by its type invarants,
- let raw_drm: *mut Self = unsafe {
+ let raw_drm: *mut Device<T, AnyCtx> = unsafe {
bindings::__drm_dev_alloc(
dev.as_raw(),
&Self::VTABLE,
layout.size(),
- mem::offset_of!(Self, dev),
+ mem::offset_of!(Device<T, AnyCtx>, dev),
)
}
.cast();
@@ -123,7 +182,7 @@ pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<A
unsafe { data.__pinned_init(raw_data) }.inspect_err(|_| {
// SAFETY: `raw_drm` is a valid pointer to `Self`, given that `__drm_dev_alloc` was
// successful.
- let drm_dev = unsafe { Self::into_drm_device(raw_drm) };
+ let drm_dev = unsafe { Device::into_drm_device(raw_drm) };
// SAFETY: `__drm_dev_alloc()` was successful, hence `drm_dev` must be valid and the
// refcount must be non-zero.
@@ -132,9 +191,40 @@ pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<A
// SAFETY: The reference count is one, and now we take ownership of that reference as a
// `drm::Device`.
- Ok(unsafe { ARef::from_raw(raw_drm) })
+ // INVARIANT: We just created the device above, but have yet to call `drm_dev_register`.
+ // This proves that `raw_drm` must be unregistered.
+ Ok(Self(unsafe { ARef::from_raw(raw_drm) }))
}
+}
+
+/// A typed DRM device with a specific [`drm::Driver`] implementation and [`DeviceCtx`].
+///
+/// Since DRM devices can be used before being fully initialized and registered with userspace, this
+/// type keeps track of whether it is known at compile-time that a device has been registered with
+/// userspace at least once using the type parameter `Ctx`.
+///
+/// Keep in mind: this means that an unregistered device can still have the registration state
+/// [`Registered`] as long as it was registered with userspace once in the past, and that the
+/// behavior of such a device is still well-defined. In such a situation, the behavior of any
+/// functions which interact with userspace will simply be no-ops. Additionally, a device with the
+/// registration state [`Unknown`] simply does not have a guaranteed registration state at compile
+/// time, and could be either registered or unregistered. Since there is no way to guarantee a
+/// long-lived reference to an unregistered device would remain unregistered, we do not provide a
+/// [`DeviceCtx`] for this.
+///
+/// # Invariants
+///
+/// * `self.dev` is a valid instance of a `struct device`.
+/// * The data layout of `Self` remains the same across all implementations of `Ctx`.
+/// * Any invariants for `Ctx` also apply.
+#[repr(C)]
+pub struct Device<T: drm::Driver, C: DeviceCtx = Registered> {
+ dev: Opaque<bindings::drm_device>,
+ data: T::Data,
+ _ctx: PhantomData<C>,
+}
+impl<T: drm::Driver, C: DeviceCtx> Device<T, C> {
pub(crate) fn as_raw(&self) -> *mut bindings::drm_device {
self.dev.get()
}
@@ -160,13 +250,13 @@ unsafe fn into_drm_device(ptr: NonNull<Self>) -> *mut bindings::drm_device {
///
/// # Safety
///
- /// Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count,
- /// i.e. it must be ensured that the reference count of the C `struct drm_device` `ptr` points
- /// to can't drop to zero, for the duration of this function call and the entire duration when
- /// the returned reference exists.
- ///
- /// Additionally, callers must ensure that the `struct device`, `ptr` is pointing to, is
- /// embedded in `Self`.
+ /// * Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count,
+ /// i.e. it must be ensured that the reference count of the C `struct drm_device` `ptr` points
+ /// to can't drop to zero, for the duration of this function call and the entire duration when
+ /// the returned reference exists.
+ /// * Additionally, callers must ensure that the `struct device`, `ptr` is pointing to, is
+ /// embedded in `Self`.
+ /// * Callers promise that any type invariants of `Ctx` will be upheld.
#[doc(hidden)]
pub unsafe fn from_raw<'a>(ptr: *const bindings::drm_device) -> &'a Self {
// SAFETY: By the safety requirements of this function `ptr` is a valid pointer to a
@@ -188,7 +278,26 @@ extern "C" fn release(ptr: *mut bindings::drm_device) {
}
}
-impl<T: drm::Driver> Deref for Device<T> {
+impl<T: drm::Driver> Device<T, AnyCtx> {
+ /// Assume the device has been fully initialized and registered with userspace.
+ ///
+ /// # Safety
+ ///
+ /// The caller promises that `drm_dev_register` has been called on this device.
+ pub(crate) unsafe fn assume_registered(&self) -> &Device<T, Registered> {
+ // SAFETY: The data layout is identical via our type invariants.
+ unsafe { mem::transmute(self) }
+ }
+}
+
+impl<T: drm::Driver, C: DeviceCtx> AsRef<Device<T, AnyCtx>> for Device<T, C> {
+ fn as_ref(&self) -> &Device<T, AnyCtx> {
+ // SAFETY: The data layout is identical via our type invariants.
+ unsafe { mem::transmute(self) }
+ }
+}
+
+impl<T: drm::Driver, C: DeviceCtx> Deref for Device<T, C> {
type Target = T::Data;
fn deref(&self) -> &Self::Target {
@@ -198,7 +307,7 @@ fn deref(&self) -> &Self::Target {
// SAFETY: DRM device objects are always reference counted and the get/put functions
// satisfy the requirements.
-unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
+unsafe impl<T: drm::Driver, C: DeviceCtx> AlwaysRefCounted for Device<T, C> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -213,7 +322,7 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
-impl<T: drm::Driver> AsRef<device::Device> for Device<T> {
+impl<T: drm::Driver, C: DeviceCtx> AsRef<device::Device> for Device<T, C> {
fn as_ref(&self) -> &device::Device {
// SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
// which is guaranteed by the type invariant.
@@ -222,8 +331,8 @@ fn as_ref(&self) -> &device::Device {
}
// SAFETY: A `drm::Device` can be released from any thread.
-unsafe impl<T: drm::Driver> Send for Device<T> {}
+unsafe impl<T: drm::Driver, C: DeviceCtx> Send for Device<T, C> {}
// SAFETY: A `drm::Device` can be shared among threads because all immutable methods are protected
// by the synchronization in `struct drm_device`.
-unsafe impl<T: drm::Driver> Sync for Device<T> {}
+unsafe impl<T: drm::Driver, C: DeviceCtx> Sync for Device<T, C> {}
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index f30ee4c6245cd..fde0447566bef 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -10,6 +10,7 @@
prelude::*,
sync::aref::ARef,
};
+use core::{mem, ptr::NonNull};
use macros::vtable;
/// Driver use the GEM memory manager. This should be set for all modern drivers.
@@ -122,30 +123,46 @@ pub trait Driver {
impl<T: Driver> Registration<T> {
/// Creates a new [`Registration`] and registers it.
- fn new(drm: &drm::Device<T>, flags: usize) -> Result<Self> {
+ fn new(drm: drm::UnregisteredDevice<T>, flags: usize) -> Result<Self> {
// SAFETY: `drm.as_raw()` is valid by the invariants of `drm::Device`.
to_result(unsafe { bindings::drm_dev_register(drm.as_raw(), flags) })?;
- Ok(Self(drm.into()))
+ // SAFETY: We just called `drm_dev_register` above
+ let new = NonNull::from(unsafe { drm.assume_registered() });
+
+ // Leak the ARef from UnregisteredDevice in preparation for transferring its ownership.
+ mem::forget(drm);
+
+ // SAFETY: `drm`'s `Drop` constructor was never called, ensuring that there remains at least
+ // one reference to the device - which we take ownership over here.
+ let new = unsafe { ARef::from_raw(new) };
+
+ Ok(Self(new))
}
- /// Same as [`Registration::new`}, but transfers ownership of the [`Registration`] to
+ /// Same as [`Registration::new`], but transfers ownership of the [`Registration`] to
/// [`devres::register`].
- pub fn new_foreign_owned(
- drm: &drm::Device<T>,
- dev: &device::Device<device::Bound>,
+ pub fn new_foreign_owned<'a>(
+ drm: drm::UnregisteredDevice<T>,
+ dev: &'a device::Device<device::Bound>,
flags: usize,
- ) -> Result
+ ) -> Result<&'a drm::Device<T>>
where
T: 'static,
{
- if drm.as_ref().as_raw() != dev.as_raw() {
+ let this_dev: &device::Device = drm.as_ref();
+ if this_dev.as_raw() != dev.as_raw() {
return Err(EINVAL);
}
let reg = Registration::<T>::new(drm, flags)?;
+ let drm = NonNull::from(reg.device());
+
+ devres::register(dev, reg, GFP_KERNEL)?;
- devres::register(dev, reg, GFP_KERNEL)
+ // SAFETY: Since `reg` was passed to devres::register(), the device now owns the lifetime
+ // of the DRM registration - ensuring that this references lives for at least as long as 'a.
+ Ok(unsafe { drm.as_ref() })
}
/// Returns a reference to the `Device` instance for this registration.
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index 1b82b6945edf2..90018edef3236 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -8,7 +8,11 @@
pub mod gem;
pub mod ioctl;
+pub use self::device::AnyCtx;
pub use self::device::Device;
+pub use self::device::DeviceCtx;
+pub use self::device::Registered;
+pub use self::device::UnregisteredDevice;
pub use self::driver::Driver;
pub use self::driver::DriverInfo;
pub use self::driver::Registration;
--
2.51.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] rust/drm/gem: Use DeviceCtx with GEM objects
2025-11-07 19:23 [PATCH 0/2] rust: drm: Introduce DeviceCtx Lyude Paul
2025-11-07 19:23 ` [PATCH 1/2] " Lyude Paul
@ 2025-11-07 19:23 ` Lyude Paul
1 sibling, 0 replies; 3+ messages in thread
From: Lyude Paul @ 2025-11-07 19:23 UTC (permalink / raw)
To: linux-kernel, rust-for-linux, dri-devel
Cc: Danilo Krummrich, Alice Ryhl, David Airlie, Simona Vetter,
Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Miguel Ojeda,
Alex Gaynor, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Trevor Gross, Daniel Almeida,
Asahi Lina, Shankari Anand,
open list:DRM DRIVER FOR NVIDIA GPUS [RUST]
Now that we have the ability to represent the context in which a DRM device
is in at compile-time, we can start carrying around this context with GEM
object types in order to allow a driver to safely create GEM objects before
a DRM device has registered with userspace.
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
drivers/gpu/drm/nova/driver.rs | 2 +-
drivers/gpu/drm/nova/gem.rs | 11 +++---
drivers/gpu/drm/tyr/driver.rs | 2 +-
drivers/gpu/drm/tyr/gem.rs | 3 +-
rust/kernel/drm/device.rs | 14 ++++----
rust/kernel/drm/driver.rs | 2 +-
rust/kernel/drm/gem/mod.rs | 66 ++++++++++++++++++++++------------
7 files changed, 63 insertions(+), 37 deletions(-)
diff --git a/drivers/gpu/drm/nova/driver.rs b/drivers/gpu/drm/nova/driver.rs
index c78d69d5f045a..54245ee439042 100644
--- a/drivers/gpu/drm/nova/driver.rs
+++ b/drivers/gpu/drm/nova/driver.rs
@@ -59,7 +59,7 @@ fn probe(adev: &auxiliary::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBo
impl drm::Driver for NovaDriver {
type Data = NovaData;
type File = File;
- type Object = gem::Object<NovaObject>;
+ type Object<Ctx: drm::DeviceCtx> = gem::Object<NovaObject, Ctx>;
const INFO: drm::DriverInfo = INFO;
diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
index 2760ba4f3450b..14d275dc74ce7 100644
--- a/drivers/gpu/drm/nova/gem.rs
+++ b/drivers/gpu/drm/nova/gem.rs
@@ -2,7 +2,7 @@
use kernel::{
drm,
- drm::{gem, gem::BaseObject},
+ drm::{gem, gem::BaseObject, DeviceCtx},
prelude::*,
sync::aref::ARef,
};
@@ -19,21 +19,24 @@ pub(crate) struct NovaObject {}
impl gem::DriverObject for NovaObject {
type Driver = NovaDriver;
- fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> {
+ fn new<Ctx: DeviceCtx>(_dev: &NovaDevice<Ctx>, _size: usize) -> impl PinInit<Self, Error> {
try_pin_init!(NovaObject {})
}
}
impl NovaObject {
/// Create a new DRM GEM object.
- pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self>>> {
+ pub(crate) fn new<Ctx: DeviceCtx>(
+ dev: &NovaDevice<Ctx>,
+ size: usize,
+ ) -> Result<ARef<gem::Object<Self, Ctx>>> {
let aligned_size = size.next_multiple_of(1 << 12);
if size == 0 || size > aligned_size {
return Err(EINVAL);
}
- gem::Object::new(dev, aligned_size)
+ gem::Object::<Self, Ctx>::new(dev, aligned_size)
}
/// Look up a GEM object handle for a `File` and return an `ObjectRef` for it.
diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index e3ea5ad85f49b..78fc08945e08e 100644
--- a/drivers/gpu/drm/tyr/driver.rs
+++ b/drivers/gpu/drm/tyr/driver.rs
@@ -187,7 +187,7 @@ fn drop(self: Pin<&mut Self>) {
impl drm::Driver for TyrDriver {
type Data = TyrData;
type File = File;
- type Object = drm::gem::Object<TyrObject>;
+ type Object<R: drm::DeviceCtx> = drm::gem::Object<TyrObject, R>;
const INFO: drm::DriverInfo = INFO;
diff --git a/drivers/gpu/drm/tyr/gem.rs b/drivers/gpu/drm/tyr/gem.rs
index 1273bf89dbd5d..5e1403409f468 100644
--- a/drivers/gpu/drm/tyr/gem.rs
+++ b/drivers/gpu/drm/tyr/gem.rs
@@ -3,6 +3,7 @@
use crate::driver::TyrDevice;
use crate::driver::TyrDriver;
use kernel::drm::gem;
+use kernel::drm::DeviceCtx;
use kernel::prelude::*;
/// GEM Object inner driver data
@@ -12,7 +13,7 @@ pub(crate) struct TyrObject {}
impl gem::DriverObject for TyrObject {
type Driver = TyrDriver;
- fn new(_dev: &TyrDevice, _size: usize) -> impl PinInit<Self, Error> {
+ fn new<Ctx: DeviceCtx>(_dev: &TyrDevice<Ctx>, _size: usize) -> impl PinInit<Self, Error> {
try_pin_init!(TyrObject {})
}
}
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 00072984930a3..227df6bf88c31 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -127,13 +127,13 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
master_set: None,
master_drop: None,
debugfs_init: None,
- gem_create_object: T::Object::ALLOC_OPS.gem_create_object,
- prime_handle_to_fd: T::Object::ALLOC_OPS.prime_handle_to_fd,
- prime_fd_to_handle: T::Object::ALLOC_OPS.prime_fd_to_handle,
- gem_prime_import: T::Object::ALLOC_OPS.gem_prime_import,
- gem_prime_import_sg_table: T::Object::ALLOC_OPS.gem_prime_import_sg_table,
- dumb_create: T::Object::ALLOC_OPS.dumb_create,
- dumb_map_offset: T::Object::ALLOC_OPS.dumb_map_offset,
+ gem_create_object: T::Object::<AnyCtx>::ALLOC_OPS.gem_create_object,
+ prime_handle_to_fd: T::Object::<AnyCtx>::ALLOC_OPS.prime_handle_to_fd,
+ prime_fd_to_handle: T::Object::<AnyCtx>::ALLOC_OPS.prime_fd_to_handle,
+ gem_prime_import: T::Object::<AnyCtx>::ALLOC_OPS.gem_prime_import,
+ gem_prime_import_sg_table: T::Object::<AnyCtx>::ALLOC_OPS.gem_prime_import_sg_table,
+ dumb_create: T::Object::<AnyCtx>::ALLOC_OPS.dumb_create,
+ dumb_map_offset: T::Object::<AnyCtx>::ALLOC_OPS.dumb_map_offset,
show_fdinfo: None,
fbdev_probe: None,
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index fde0447566bef..4e8735e9018c4 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -104,7 +104,7 @@ pub trait Driver {
type Data: Sync + Send;
/// The type used to manage memory for this driver.
- type Object: AllocImpl;
+ type Object<Ctx: drm::DeviceCtx>: AllocImpl;
/// The type used to represent a DRM File (client)
type File: drm::file::DriverFile;
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index eb5f3feac8907..62ca11126e1c0 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -7,13 +7,16 @@
use crate::{
alloc::flags::*,
bindings, drm,
- drm::driver::{AllocImpl, AllocOps},
+ drm::{
+ device::{DeviceCtx, Registered},
+ driver::{AllocImpl, AllocOps},
+ },
error::{to_result, Result},
prelude::*,
sync::aref::{ARef, AlwaysRefCounted},
types::Opaque,
};
-use core::{ops::Deref, ptr::NonNull};
+use core::{marker::PhantomData, ops::Deref, ptr::NonNull};
/// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
/// [`DriverObject`] implementation.
@@ -22,21 +25,30 @@
/// [`DriverFile`]: drm::file::DriverFile
pub type DriverFile<T> = drm::File<<<T as DriverObject>::Driver as drm::Driver>::File>;
+/// A type alias for retrieving the current [`AllocImpl`] for a given [`DriverObject`].
+///
+/// [`Driver`]: drm::Driver
+pub type DriverAllocImpl<T, Ctx = Registered> =
+ <<T as DriverObject>::Driver as drm::Driver>::Object<Ctx>;
+
/// GEM object functions, which must be implemented by drivers.
pub trait DriverObject: Sync + Send + Sized {
/// Parent `Driver` for this object.
type Driver: drm::Driver;
/// Create a new driver data object for a GEM object of a given size.
- fn new(dev: &drm::Device<Self::Driver>, size: usize) -> impl PinInit<Self, Error>;
+ fn new<Ctx: DeviceCtx>(
+ dev: &drm::Device<Self::Driver, Ctx>,
+ size: usize,
+ ) -> impl PinInit<Self, Error>;
/// Open a new handle to an existing object, associated with a File.
- fn open(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) -> Result {
+ fn open(_obj: &DriverAllocImpl<Self>, _file: &DriverFile<Self>) -> Result {
Ok(())
}
/// Close a handle to an existing object, associated with a File.
- fn close(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) {}
+ fn close(_obj: &DriverAllocImpl<Self>, _file: &DriverFile<Self>) {}
}
/// Trait that represents a GEM object subtype
@@ -62,9 +74,12 @@ extern "C" fn open_callback<T: DriverObject>(
// SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
let file = unsafe { DriverFile::<T>::from_raw(raw_file) };
- // SAFETY: `open_callback` is specified in the AllocOps structure for `DriverObject<T>`,
- // ensuring that `raw_obj` is contained within a `DriverObject<T>`
- let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj) };
+ // SAFETY:
+ // * `open_callback` is specified in the AllocOps structure for `DriverObject`, ensuring that
+ // `raw_obj` is contained within a `DriverAllocImpl<T>`
+ // * It is only possible for `open_callback` to be called after device registration, ensuring
+ // that the object's device is in the `Registered` state.
+ let obj: &DriverAllocImpl<T> = unsafe { IntoGEMObject::from_raw(raw_obj) };
match T::open(obj, file) {
Err(e) => e.to_errno(),
@@ -81,12 +96,12 @@ extern "C" fn close_callback<T: DriverObject>(
// SAFETY: `close_callback` is specified in the AllocOps structure for `Object<T>`, ensuring
// that `raw_obj` is indeed contained within a `Object<T>`.
- let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj) };
+ let obj: &DriverAllocImpl<T> = unsafe { IntoGEMObject::from_raw(raw_obj) };
T::close(obj, file);
}
-impl<T: DriverObject> IntoGEMObject for Object<T> {
+impl<T: DriverObject, Ctx: DeviceCtx> IntoGEMObject for Object<T, Ctx> {
fn as_raw(&self) -> *mut bindings::drm_gem_object {
self.obj.get()
}
@@ -94,7 +109,7 @@ fn as_raw(&self) -> *mut bindings::drm_gem_object {
unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self {
// SAFETY: `obj` is guaranteed to be in an `Object<T>` via the safety contract of this
// function
- unsafe { &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T>, obj) }
+ unsafe { &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T, Ctx>, obj) }
}
}
@@ -111,7 +126,7 @@ fn size(&self) -> usize {
fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
where
Self: AllocImpl<Driver = D>,
- D: drm::Driver<Object = Self, File = F>,
+ D: drm::Driver<Object<Registered> = Self, File = F>,
F: drm::file::DriverFile<Driver = D>,
{
let mut handle: u32 = 0;
@@ -126,7 +141,7 @@ fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
fn lookup_handle<D, F>(file: &drm::File<F>, handle: u32) -> Result<ARef<Self>>
where
Self: AllocImpl<Driver = D>,
- D: drm::Driver<Object = Self, File = F>,
+ D: drm::Driver<Object<Registered> = Self, File = F>,
F: drm::file::DriverFile<Driver = D>,
{
// SAFETY: The arguments are all valid per the type invariants.
@@ -166,16 +181,18 @@ impl<T: IntoGEMObject> BaseObject for T {}
///
/// Invariants
///
-/// - `self.obj` is a valid instance of a `struct drm_gem_object`.
+/// * `self.obj` is a valid instance of a `struct drm_gem_object`.
+/// * Any type invariants of `Ctx` apply to the parent DRM device for this GEM object.
#[repr(C)]
#[pin_data]
-pub struct Object<T: DriverObject + Send + Sync> {
+pub struct Object<T: DriverObject + Send + Sync, Ctx: DeviceCtx = Registered> {
obj: Opaque<bindings::drm_gem_object>,
#[pin]
data: T,
+ _ctx: PhantomData<Ctx>,
}
-impl<T: DriverObject> Object<T> {
+impl<T: DriverObject, Ctx: DeviceCtx> Object<T, Ctx> {
const OBJECT_FUNCS: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
free: Some(Self::free_callback),
open: Some(open_callback::<T>),
@@ -195,11 +212,12 @@ impl<T: DriverObject> Object<T> {
};
/// Create a new GEM object.
- pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
+ pub fn new(dev: &drm::Device<T::Driver, Ctx>, size: usize) -> Result<ARef<Self>> {
let obj: Pin<KBox<Self>> = KBox::pin_init(
try_pin_init!(Self {
obj: Opaque::new(bindings::drm_gem_object::default()),
data <- T::new(dev, size),
+ _ctx: PhantomData,
}),
GFP_KERNEL,
)?;
@@ -208,6 +226,8 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
unsafe { (*obj.as_raw()).funcs = &Self::OBJECT_FUNCS };
// SAFETY: The arguments are all valid per the type invariants.
+ // INVARIANT: We use `dev` for creating the GEM object, which is known to be in state `Ctx` -
+ // ensuring that the GEM object's pointer to the DRM device is always in the same state.
to_result(unsafe { bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size) })?;
// SAFETY: We never move out of `Self`.
@@ -221,13 +241,15 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
}
/// Returns the `Device` that owns this GEM object.
- pub fn dev(&self) -> &drm::Device<T::Driver> {
+ pub fn dev(&self) -> &drm::Device<T::Driver, Ctx> {
// SAFETY:
// - `struct drm_gem_object.dev` is initialized and valid for as long as the GEM
// object lives.
// - The device we used for creating the gem object is passed as &drm::Device<T::Driver> to
// Object::<T>::new(), so we know that `T::Driver` is the right generic parameter to use
// here.
+ // - Any type invariants of `Ctx` are upheld by using the same `Ctx` for the `Device` we
+ // return.
unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
}
@@ -253,7 +275,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
}
// SAFETY: Instances of `Object<T>` are always reference-counted.
-unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {
+unsafe impl<T: DriverObject, Ctx: DeviceCtx> crate::types::AlwaysRefCounted for Object<T, Ctx> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_gem_object_get(self.as_raw()) };
@@ -268,9 +290,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
-impl<T: DriverObject> super::private::Sealed for Object<T> {}
+impl<T: DriverObject, Ctx: DeviceCtx> super::private::Sealed for Object<T, Ctx> {}
-impl<T: DriverObject> Deref for Object<T> {
+impl<T: DriverObject, Ctx: DeviceCtx> Deref for Object<T, Ctx> {
type Target = T;
fn deref(&self) -> &Self::Target {
@@ -278,7 +300,7 @@ fn deref(&self) -> &Self::Target {
}
}
-impl<T: DriverObject> AllocImpl for Object<T> {
+impl<T: DriverObject, Ctx: DeviceCtx> AllocImpl for Object<T, Ctx> {
type Driver = T::Driver;
const ALLOC_OPS: AllocOps = AllocOps {
--
2.51.1
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