From: Asahi Lina <l...@asahilina.net>
A DRM File is the DRM counterpart to a kernel file structure,
representing an open DRM file descriptor.
Add a Rust abstraction to allow drivers to implement their own File types
that implement the DriverFile trait.
Reviewed-by: Maxime Ripard <mrip...@kernel.org>
Signed-off-by: Asahi Lina <l...@asahilina.net>
[ Rework of drm::File
* switch to the Opaque<T> type
* fix (mutable) references to struct drm_file (which in this context
is UB)
* restructure and rename functions to align with common kernel
schemes
* write and fix safety and invariant comments
* remove necessity for and convert 'as' casts
* original source archive: https://archive.is/GH8oy
- Danilo ]
Signed-off-by: Danilo Krummrich <d...@kernel.org>
---
rust/bindings/bindings_helper.h | 1 +
rust/kernel/drm/device.rs | 4 +-
rust/kernel/drm/driver.rs | 3 +
rust/kernel/drm/file.rs | 99 +++++++++++++++++++++++++++++++++
rust/kernel/drm/mod.rs | 2 +
5 files changed, 107 insertions(+), 2 deletions(-)
create mode 100644 rust/kernel/drm/file.rs
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 1dd7100c1cff..e39fb4210710 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -8,6 +8,7 @@
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
+#include <drm/drm_file.h>
#include <drm/drm_ioctl.h>
#include <kunit/test.h>
#include <linux/blk-mq.h>
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index c5433d314409..f7d7abf83fa4 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -58,8 +58,8 @@ pub struct Device<T: drm::Driver> {
impl<T: drm::Driver> Device<T> {
const VTABLE: bindings::drm_driver = drm_legacy_fields! {
load: None,
- open: None, // TODO: File abstraction
- postclose: None, // TODO: File abstraction
+ open: Some(drm::File::<T::File>::open_callback),
+ postclose: Some(drm::File::<T::File>::postclose_callback),
unload: None,
release: None,
master_set: None,
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 96bb287eada2..24c2225b5d28 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -109,6 +109,9 @@ pub trait Driver {
/// Should be either `drm::gem::Object<T>` or `drm::gem::shmem::Object<T>`.
type Object: AllocImpl;
+ /// The type used to represent a DRM File (client)
+ type File: drm::file::DriverFile;
+
/// Driver metadata
const INFO: DriverInfo;
diff --git a/rust/kernel/drm/file.rs b/rust/kernel/drm/file.rs
new file mode 100644
index 000000000000..3b97728f03e0
--- /dev/null
+++ b/rust/kernel/drm/file.rs
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! DRM File objects.
+//!
+//! C header:
[`include/linux/drm/drm_file.h`](srctree/include/linux/drm/drm_file.h)
+
+use crate::{bindings, drm, error::Result, prelude::*, types::Opaque};
+use core::marker::PhantomData;
+use core::pin::Pin;
+
+/// Trait that must be implemented by DRM drivers to represent a DRM File (a
client instance).
+pub trait DriverFile {
+ /// The parent `Driver` implementation for this `DriverFile`.
+ type Driver: drm::Driver;
+
+ /// Open a new file (called when a client opens the DRM device).
+ fn open(device: &drm::Device<Self::Driver>) -> Result<Pin<KBox<Self>>>;
+}
+
+/// An open DRM File.
+///
+/// # Invariants
+///
+/// `self.0` is always a valid pointer to an open `struct drm_file`.
+#[repr(transparent)]
+pub struct File<T: DriverFile>(Opaque<bindings::drm_file>, PhantomData<T>);
+
+impl<T: DriverFile> File<T> {
+ #[doc(hidden)]
+ /// Not intended to be called externally, except via declare_drm_ioctls!()
+ ///
+ /// # Safety
+ ///
+ /// `raw_file` must be a valid pointer to an open `struct drm_file`,
opened through `T::open`.
+ pub unsafe fn as_ref<'a>(ptr: *mut bindings::drm_file) -> &'a File<T> {
+ // SAFETY: `raw_file` is valid by the safety requirements of this
function.
+ unsafe { &*ptr.cast() }
+ }
+
+ pub(super) fn as_raw(&self) -> *mut bindings::drm_file {
+ self.0.get()
+ }
+
+ fn driver_priv(&self) -> *mut T {
+ // SAFETY: By the type invariants of `Self`, `self.as_raw()` is always
valid.
+ unsafe { (*self.as_raw()).driver_priv }.cast()
+ }
+
+ /// Return a pinned reference to the driver file structure.
+ pub fn inner(&self) -> Pin<&T> {
+ // SAFETY: By the type invariant the pointer `self.as_raw()` points to
a valid and opened
+ // `struct drm_file`, hence `driver_priv` has been properly
initialized by `open_callback`.
+ unsafe { Pin::new_unchecked(&*(self.driver_priv())) }
+ }
+
+ /// The open callback of a `struct drm_file`.
+ pub(crate) extern "C" fn open_callback(
+ raw_dev: *mut bindings::drm_device,
+ raw_file: *mut bindings::drm_file,
+ ) -> core::ffi::c_int {
+ // SAFETY: A callback from `struct drm_driver::open` guarantees that
+ // - `raw_dev` is valid pointer to a `sturct drm_device`,
+ // - the corresponding `sturct drm_device` has been registered.
+ let drm = unsafe { drm::Device::as_ref(raw_dev) };
+
+ // SAFETY: `raw_file` valid pointer to a `struct drm_file`.
+ let file = unsafe { File::<T>::as_ref(raw_file) };
+
+ let inner = match T::open(drm) {
+ Err(e) => {
+ return e.to_errno();
+ }
+ Ok(i) => i,
+ };
+
+ // SAFETY: This pointer is treated as pinned, and the Drop guarantee
is upheld in
+ // `postclose_callback()`.
+ let driver_priv = KBox::into_raw(unsafe {
Pin::into_inner_unchecked(inner) });
+
+ // SAFETY: By the type invariants of `Self`, `self.as_raw()` is always
valid.
+ unsafe { (*file.as_raw()).driver_priv = driver_priv.cast() };
+
+ 0
+ }
+
+ /// The postclose callback of a `struct drm_file`.
+ pub(crate) extern "C" fn postclose_callback(
+ _raw_dev: *mut bindings::drm_device,
+ raw_file: *mut bindings::drm_file,
+ ) {
+ // SAFETY: This reference won't escape this function
+ let file = unsafe { File::<T>::as_ref(raw_file) };
+
+ // SAFETY: `file.driver_priv` has been created in `open_callback`
through `KBox::into_raw`.
+ let _ = unsafe { KBox::from_raw(file.driver_priv()) };
+ }
+}
+
+impl<T: DriverFile> super::private::Sealed for File<T> {}
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index 2d88e70ba607..b36223e5bd98 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -4,12 +4,14 @@
pub mod device;
pub mod driver;
+pub mod file;
pub mod ioctl;
pub use self::device::Device;
pub use self::driver::Driver;
pub use self::driver::DriverInfo;
pub use self::driver::Registration;
+pub use self::file::File;
pub(crate) mod private {
pub trait Sealed {}
--
2.49.0
