[PATCH v2 09/11] rust: driver: remove open-coded matching logic

[Gary Guo <gary@garyguo.net>]

With device ID info now including pointers instead of indices, the
open-coded ACPI/OF matching is no longer needed and can be replaced with
`device_get_match_data`.

With the removal of open-coded matching, the exposed functions and helpers
are also removed; this effectively reverts most of commit 2690d071584e
("rust: ACPI: fix missing match data for PRP0001").

Signed-off-by: Gary Guo <gary@garyguo.net>
---
 MAINTAINERS             |   1 -
 drivers/acpi/bus.c      |   6 +--
 include/acpi/acpi_bus.h |  11 ----
 rust/helpers/acpi.c     |  16 ------
 rust/helpers/helpers.c  |   1 -
 rust/kernel/driver.rs   | 137 ++++--------------------------------------------
 rust/kernel/i2c.rs      |   6 ++-
 rust/kernel/platform.rs |   3 +-
 8 files changed, 20 insertions(+), 161 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 15011f5752a9..07240e0b7451 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -297,7 +297,6 @@ F:	include/linux/acpi.h
 F:	include/linux/fwnode.h
 F:	include/linux/fw_table.h
 F:	lib/fw_table.c
-F:	rust/helpers/acpi.c
 F:	rust/kernel/acpi.rs
 F:	tools/power/acpi/
 
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a30a904f6535..1fb0b10bf924 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -898,9 +898,9 @@ const struct acpi_device *acpi_companion_match(const struct device *dev)
  * identifiers and a _DSD object with the "compatible" property, use that
  * property to match against the given list of identifiers.
  */
-bool acpi_of_match_device(const struct acpi_device *adev,
-			  const struct of_device_id *of_match_table,
-			  const struct of_device_id **of_id)
+static bool acpi_of_match_device(const struct acpi_device *adev,
+				 const struct of_device_id *of_match_table,
+				 const struct of_device_id **of_id)
 {
 	const union acpi_object *of_compatible, *obj;
 	int i, nval;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 714d111d8053..7e57f9698f7c 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -189,10 +189,6 @@ struct acpi_driver {
  * -----------
  */
 
-bool acpi_of_match_device(const struct acpi_device *adev,
-			  const struct of_device_id *of_match_table,
-			  const struct of_device_id **of_id);
-
 /* Status (_STA) */
 
 struct acpi_device_status {
@@ -1000,13 +996,6 @@ int acpi_scan_add_dep(acpi_handle handle, struct acpi_handle_list *dep_devices);
 u32 arch_acpi_add_auto_dep(acpi_handle handle);
 #else	/* CONFIG_ACPI */
 
-static inline bool acpi_of_match_device(const struct acpi_device *adev,
-					const struct of_device_id *of_match_table,
-					const struct of_device_id **of_id)
-{
-	return false;
-}
-
 static inline int register_acpi_bus_type(void *bus) { return 0; }
 static inline int unregister_acpi_bus_type(void *bus) { return 0; }
 
diff --git a/rust/helpers/acpi.c b/rust/helpers/acpi.c
deleted file mode 100644
index e75c9807bbad..000000000000
--- a/rust/helpers/acpi.c
+++ /dev/null
@@ -1,16 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/acpi.h>
-#include <acpi/acpi_bus.h>
-
-__rust_helper bool rust_helper_acpi_of_match_device(const struct acpi_device *adev,
-						    const struct of_device_id *of_match_table,
-						    const struct of_device_id **of_id)
-{
-	return acpi_of_match_device(adev, of_match_table, of_id);
-}
-
-__rust_helper struct acpi_device *rust_helper_to_acpi_device_node(struct fwnode_handle *fwnode)
-{
-	return to_acpi_device_node(fwnode);
-}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 998e31052e66..fadd7acdd81c 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -38,7 +38,6 @@
 #define __rust_helper __always_inline
 #endif
 
-#include "acpi.c"
 #include "atomic.c"
 #include "atomic_ext.c"
 #include "auxiliary.c"
diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index 824899d76fed..c9c74c4dde8f 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -107,7 +107,6 @@
 use crate::{
     acpi,
     device,
-    device_id::RawDeviceIdIndex,
     of,
     prelude::*,
     types::Opaque,
@@ -292,26 +291,6 @@ fn init(
     }
 }
 
-// Calling the FFI function directly from the `Adapter` impl may result in it being called
-// directly from driver modules. This happens since the Rust compiler will use monomorphisation, so
-// it might happen that functions are instantiated within the calling driver module. For now, work
-// around this with `#[inline(never)]` helpers.
-//
-// TODO: Remove once a more generic solution has been implemented. For instance, we may be able to
-// leverage `bindgen` to take care of this depending on whether a symbol is (already) exported.
-#[inline(never)]
-#[allow(clippy::missing_safety_doc)]
-#[allow(dead_code)]
-#[must_use]
-unsafe fn acpi_of_match_device(
-    adev: *const bindings::acpi_device,
-    of_match_table: *const bindings::of_device_id,
-    of_id: *mut *const bindings::of_device_id,
-) -> bool {
-    // SAFETY: Safety requirements are the same as `bindings::acpi_of_match_device`.
-    unsafe { bindings::acpi_of_match_device(adev, of_match_table, of_id) }
-}
-
 /// 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
@@ -325,117 +304,23 @@ pub trait Adapter {
     /// The [`acpi::IdTable`] of the corresponding driver
     fn acpi_id_table() -> Option<acpi::IdTable<Self::IdInfo>>;
 
-    /// Returns the driver's private data from the matching entry in the [`acpi::IdTable`], if any.
-    ///
-    /// If this returns `None`, it means there is no match with an entry in the [`acpi::IdTable`].
-    fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
-        #[cfg(not(CONFIG_ACPI))]
-        {
-            let _ = dev;
-            None
-        }
-
-        #[cfg(CONFIG_ACPI)]
-        {
-            let table = Self::acpi_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 `dev.as_raw()`.
-            let raw_id = unsafe { bindings::acpi_match_device(table.as_ptr(), dev.as_raw()) };
-
-            if raw_id.is_null() {
-                None
-            } else {
-                // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct acpi_device_id`
-                // and does not add additional invariants, so it's safe to transmute.
-                let id = unsafe { &*raw_id.cast::<acpi::DeviceId>() };
-
-                // SAFETY: `id` comes from `table` which is of type `IdArray<_, Self::IdInfo>`.
-                Some(unsafe { id.info_unchecked::<Self::IdInfo>() })
-            }
-        }
-    }
-
     /// The [`of::IdTable`] of the corresponding driver.
     fn of_id_table() -> Option<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`].
-    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
-        let table = Self::of_id_table()?;
-
-        #[cfg(not(any(CONFIG_OF, CONFIG_ACPI)))]
-        {
-            let _ = (dev, table);
-        }
-
-        #[cfg(CONFIG_OF)]
-        {
-            // SAFETY:
-            // - `table` has static lifetime, hence it's valid for read,
-            // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
-            let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
-
-            if !raw_id.is_null() {
-                // 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>() };
-
-                // SAFETY: `id` comes from `table` which is of type `IdArray<_, Self::IdInfo>`.
-                return Some(unsafe { id.info_unchecked::<Self::IdInfo>() });
-            }
-        }
-
-        #[cfg(CONFIG_ACPI)]
-        {
-            use core::ptr;
-            use device::property::FwNode;
-
-            let mut raw_id = ptr::null();
-
-            let fwnode = dev.fwnode().map_or(ptr::null_mut(), FwNode::as_raw);
-
-            // SAFETY: `fwnode` is a pointer to a valid `fwnode_handle`. A null pointer will be
-            // passed through the function.
-            let adev = unsafe { bindings::to_acpi_device_node(fwnode) };
-
-            // SAFETY:
-            // - `adev` is a valid pointer to `acpi_device` or is null. It is guaranteed to be
-            //   valid as long as `dev` is alive.
-            // - `table` has static lifetime, hence it's valid for read.
-            if unsafe { acpi_of_match_device(adev, table.as_ptr(), &raw mut raw_id) } {
-                // SAFETY:
-                // - the function returns true, therefore `raw_id` has been set to a pointer to a
-                //   valid `of_device_id`.
-                // - `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>() };
-
-                // SAFETY: `id` comes from `table` which is of type `IdArray<_, Self::IdInfo>`.
-                return Some(unsafe { id.info_unchecked::<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::acpi_id_info(dev);
-        if id.is_some() {
-            return id;
-        }
-
-        let id = Self::of_id_info(dev);
-        if id.is_some() {
-            return id;
-        }
-
-        None
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the `dev` matched data is of type `Self::IdInfo`.
+    #[inline]
+    unsafe fn id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        // SAFETY: `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
+        let data = unsafe { bindings::device_get_match_data(dev.as_raw()) };
+
+        // SAFETY: Per safety requirement, `data` is of type `Self::IdInfo`.
+        unsafe { data.cast::<Self::IdInfo>().as_ref() }
     }
 }
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 31f2cfe6be31..2d2191164e25 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -149,8 +149,10 @@ extern "C" fn probe_callback(idev: *mut bindings::i2c_client) -> kernel::ffi::c_
         // INVARIANT: `idev` is valid for the duration of `probe_callback()`.
         let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal<'_>>>() };
 
-        let info =
-            Self::i2c_id_info(idev).or_else(|| <Self as driver::Adapter>::id_info(idev.as_ref()));
+        let info = Self::i2c_id_info(idev).or_else(|| {
+            // SAFETY: `idev` matched data is of type `Self::IdInfo`.
+            unsafe { <Self as driver::Adapter>::id_info(idev.as_ref()) }
+        });
 
         from_result(|| {
             let data = T::probe(idev, info);
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 210a815925ce..e12e88113ca5 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -100,7 +100,8 @@ extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ff
         //
         // INVARIANT: `pdev` is valid for the duration of `probe_callback()`.
         let pdev = unsafe { &*pdev.cast::<Device<device::CoreInternal<'_>>>() };
-        let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
+        // SAFETY: `pdev` matched data is of type `Self::IdInfo`.
+        let info = unsafe { <Self as driver::Adapter>::id_info(pdev.as_ref()) };
 
         from_result(|| {
             let data = T::probe(pdev, info);

-- 
2.54.0