[PATCH v4 4/4] rust: drm: gem: Support driver-private GEM object types
Lyude Paul
lyude at redhat.com
Tue May 20 20:35:30 UTC 2025
One of the original intents with the gem bindings was that drivers could
specify additional gem implementations, in order to enable for driver
private gem objects. This wasn't really possible however, as up until now
our GEM bindings have always assumed that the only GEM object we would run
into was driver::Driver::Object - meaning that implementing another GEM
object type would result in all of the BaseDriverObject callbacks assuming
the wrong type.
This is a pretty easy fix though, all we need to do is specify a
BaseDriverObject in driver::Driver instead of an AllocImpl, and then add an
associated type for AllocImpl in BaseDriverObject. That way each
BaseDriverObject has its own AllocImpl allowing it to know which type to
provide in BaseDriverObject callbacks, and driver::Driver can simply go
through the BaseDriverObject to its AllocImpl type in order to get access
to ALLOC_OPS.
So, let's do this and update Nova for these changes.
Signed-off-by: Lyude Paul <lyude at redhat.com>
---
V4:
* Update trait bounds. This looks gnarlier then it is:
Self: AllocImpl<Driver = D>, <-- Get the driver for this GEM object
D: drm::Driver<Object = O, File = F>, <-- Get the driver's Object, File
impl
F: drm::file::DriverFile,
O: BaseDriverObject<Object = Self>, <-- Make sure we're the driver's
main GEM object impl.
(don't worry, the compiler can always figure out what D, F, O are)
* Also, rename the commit. I realized I should be clearer about what this
does so people can stop me if this isn't what was meant by private gem
object implementations :).
Signed-off-by: Lyude Paul <lyude at redhat.com>
---
drivers/gpu/drm/nova/driver.rs | 4 ++--
drivers/gpu/drm/nova/gem.rs | 1 +
rust/kernel/drm/device.rs | 17 ++++++++++-------
rust/kernel/drm/driver.rs | 2 +-
rust/kernel/drm/gem/mod.rs | 21 +++++++++++++--------
5 files changed, 27 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/nova/driver.rs b/drivers/gpu/drm/nova/driver.rs
index b28b2e05cc156..58e534cf3ed39 100644
--- a/drivers/gpu/drm/nova/driver.rs
+++ b/drivers/gpu/drm/nova/driver.rs
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
-use kernel::{auxiliary, c_str, device::Core, drm, drm::gem, drm::ioctl, prelude::*, types::ARef};
+use kernel::{auxiliary, c_str, device::Core, drm, drm::ioctl, prelude::*, types::ARef};
use crate::file::File;
use crate::gem::NovaObject;
@@ -57,7 +57,7 @@ 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 = NovaObject;
const INFO: drm::DriverInfo = INFO;
diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
index 68f93c9675611..a3024922f0d90 100644
--- a/drivers/gpu/drm/nova/gem.rs
+++ b/drivers/gpu/drm/nova/gem.rs
@@ -18,6 +18,7 @@ pub(crate) struct NovaObject {}
impl gem::BaseDriverObject for NovaObject {
type Driver = NovaDriver;
+ type Object = gem::Object<Self>;
fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> {
try_pin_init!(NovaObject {})
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 74c9a3dd719e3..6fc6995be637d 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -60,6 +60,9 @@ pub struct Device<T: drm::Driver> {
data: T::Data,
}
+/// A type alias for referring to the [`AllocImpl`] implementation for a DRM driver.
+type DriverAllocImpl<T> = <<T as drm::Driver>::Object as drm::gem::BaseDriverObject>::Object;
+
impl<T: drm::Driver> Device<T> {
const VTABLE: bindings::drm_driver = drm_legacy_fields! {
load: None,
@@ -70,13 +73,13 @@ impl<T: drm::Driver> Device<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: DriverAllocImpl::<T>::ALLOC_OPS.gem_create_object,
+ prime_handle_to_fd: DriverAllocImpl::<T>::ALLOC_OPS.prime_handle_to_fd,
+ prime_fd_to_handle: DriverAllocImpl::<T>::ALLOC_OPS.prime_fd_to_handle,
+ gem_prime_import: DriverAllocImpl::<T>::ALLOC_OPS.gem_prime_import,
+ gem_prime_import_sg_table: DriverAllocImpl::<T>::ALLOC_OPS.gem_prime_import_sg_table,
+ dumb_create: DriverAllocImpl::<T>::ALLOC_OPS.dumb_create,
+ dumb_map_offset: DriverAllocImpl::<T>::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 2be2a2d318e03..a77747edac80e 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -106,7 +106,7 @@ pub trait Driver {
type Data: Sync + Send;
/// The type used to manage memory for this driver.
- type Object: AllocImpl;
+ type Object: drm::gem::BaseDriverObject;
/// 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 c459829ce5a5d..992e098d0a3e2 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -26,16 +26,19 @@ pub trait BaseDriverObject: Sync + Send + Sized {
/// Parent `Driver` for this object.
type Driver: drm::Driver;
+ /// The GEM object type that will be passed to various callbacks.
+ type Object: AllocImpl;
+
/// 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>;
/// 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: &Self::Object, _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: &Self::Object, _file: &DriverFile<Self>) {}
}
/// Trait that represents a GEM object subtype
@@ -83,7 +86,7 @@ extern "C" fn open_callback<T: BaseDriverObject>(
// 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>::as_ref(raw_obj) };
+ let obj = unsafe { T::Object::as_ref(raw_obj) };
match T::open(obj, file) {
Err(e) => e.to_errno(),
@@ -100,7 +103,7 @@ extern "C" fn close_callback<T: BaseDriverObject>(
// 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>::as_ref(raw_obj) };
+ let obj = unsafe { T::Object::as_ref(raw_obj) };
T::close(obj, file);
}
@@ -127,11 +130,12 @@ fn size(&self) -> usize {
/// Creates a new handle for the object associated with a given `File`
/// (or returns an existing one).
- fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
+ fn create_handle<D, F, O>(&self, file: &drm::File<F>) -> Result<u32>
where
Self: AllocImpl<Driver = D>,
- D: drm::Driver<Object = Self, File = F>,
+ D: drm::Driver<Object = O, File = F>,
F: drm::file::DriverFile,
+ O: BaseDriverObject<Object = Self>,
{
let mut handle: u32 = 0;
// SAFETY: The arguments are all valid per the type invariants.
@@ -142,11 +146,12 @@ fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
}
/// Looks up an object by its handle for a given `File`.
- fn lookup_handle<D, F>(file: &drm::File<F>, handle: u32) -> Result<ARef<Self>>
+ fn lookup_handle<D, F, O>(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 = O, File = F>,
F: drm::file::DriverFile,
+ O: BaseDriverObject<Object = Self>,
{
// SAFETY: The arguments are all valid per the type invariants.
let ptr = unsafe { bindings::drm_gem_object_lookup(file.as_raw().cast(), handle) };
--
2.49.0
More information about the dri-devel
mailing list