This is an associated type that may be used in order to specify a data-type
to pass to gem objects when construction them, allowing for drivers to more
easily initialize their private-data for gem objects.
Signed-off-by: Lyude Paul <lyude at redhat.com>
---
V3:
* s/BaseDriverObject/DriverObject/
Signed-off-by: Lyude Paul <lyude at redhat.com>
---
drivers/gpu/drm/nova/gem.rs | 5 ++-
rust/kernel/drm/gem/mod.rs | 75 +++++++++++++++++++++++++++++++++----
2 files changed, 71 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
index 10e3053f1a246..015cb56061a56 100644
--- a/drivers/gpu/drm/nova/gem.rs
+++ b/drivers/gpu/drm/nova/gem.rs
@@ -19,8 +19,9 @@ pub(crate) struct NovaObject {}
impl gem::DriverObject for NovaObject {
type Driver = NovaDriver;
type Object = gem::Object<Self>;
+ type Args = ();
- fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self,
Error> {
+ fn new(_dev: &NovaDevice, _size: usize, _args: Self::Args) -> impl
PinInit<Self, Error> {
try_pin_init!(NovaObject {})
}
}
@@ -34,7 +35,7 @@ pub(crate) fn new(dev: &NovaDevice, size: usize) ->
Result<ARef<gem::Object<Self
return Err(EINVAL);
}
- gem::Object::new(dev, aligned_size)
+ gem::Object::new(dev, aligned_size, ())
}
/// Look up a GEM object handle for a `File` and return an `ObjectRef` for
it.
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index f901d4263ee87..fe6ff3762a504 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -6,13 +6,14 @@
use crate::{
alloc::flags::*,
- bindings, drm,
+ bindings,
drm::driver::{AllocImpl, AllocOps},
+ drm::{self, private::Sealed},
error::{to_result, Result},
prelude::*,
types::{ARef, AlwaysRefCounted, 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.
@@ -21,6 +22,26 @@
/// [`DriverFile`]: drm::file::DriverFile
pub type DriverFile<T> = drm::File<<<T as
DriverObject>::Driver as drm::Driver>::File>;
+/// A helper macro for implementing AsRef<OpaqueObject<?>>
+macro_rules! impl_as_opaque {
+ ($type:ty where $tparam:ident : $tparam_trait:ident) => {
+ impl<D, $tparam>
core::convert::AsRef<kernel::drm::gem::OpaqueObject<D>> for $type
+ where
+ D: kernel::drm::driver::Driver,
+ Self: kernel::drm::gem::DriverObject<Driver = D>,
+ Self: kernel::drm::gem::IntoGEMObject,
+ $tparam: $tparam_trait,
+ {
+ fn as_ref(&self) ->
&kernel::drm::gem::OpaqueObject<D> {
+ // SAFETY: This cast is safe via our type invariant.
+ unsafe { &*((self.as_raw().cast_const()).cast()) }
+ }
+ }
+ };
+}
+
+pub(crate) use impl_as_opaque;
+
/// GEM object functions, which must be implemented by drivers.
pub trait DriverObject: Sync + Send + Sized {
/// Parent `Driver` for this object.
@@ -29,8 +50,15 @@ pub trait DriverObject: Sync + Send + Sized {
/// The GEM object type that will be passed to various callbacks.
type Object: AllocImpl;
+ /// The data type to use for passing arguments to
[`BaseDriverObject::new`].
+ type Args;
+
/// 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(
+ dev: &drm::Device<Self::Driver>,
+ size: usize,
+ args: Self::Args,
+ ) -> impl PinInit<Self, Error>;
/// Open a new handle to an existing object, associated with a File.
fn open(_obj: &Self::Object, _file: &DriverFile<Self>) ->
Result {
@@ -42,7 +70,7 @@ fn close(_obj: &Self::Object, _file:
&DriverFile<Self>) {}
}
/// Trait that represents a GEM object subtype
-pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
+pub trait IntoGEMObject: Sized + Sealed + AlwaysRefCounted {
/// Returns a reference to the raw `drm_gem_object` structure, which must
be valid as long as
/// this owning object is valid.
fn as_raw(&self) -> *mut bindings::drm_gem_object;
@@ -233,11 +261,11 @@ 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>, size: usize, args:
T::Args) -> 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),
+ data <- T::new(dev, size, args),
// INVARIANT: The drm subsystem guarantees that the `struct
drm_device` will live
// as long as the GEM object lives.
dev: dev.into(),
@@ -289,7 +317,7 @@ extern "C" fn free_callback(obj: *mut
bindings::drm_gem_object) {
}
}
-impl<T: DriverObject> super::private::Sealed for Object<T> {}
+impl<T: DriverObject> Sealed for Object<T> {}
impl<T: DriverObject> Deref for Object<T> {
type Target = T;
@@ -313,6 +341,39 @@ impl<T: DriverObject> AllocImpl for Object<T> {
};
}
+impl_as_opaque!(Object<T> where T: DriverObject);
+
+/// A GEM object whose private-data layout is not known.
+///
+/// Not all GEM objects are created equal, and subsequently drivers may
occasionally need to deal
+/// with situations where they are working with a GEM object but have no
knowledge of its
+/// private-data layout.
+///
+/// It may be used just like a normal [`Object`], with the exception that it
cannot access
+/// driver-private data.
+///
+/// # Invariant
+///
+/// Via `#[repr(transparent)]`, this type is guaranteed to have an identical
data layout to
+/// `struct drm_gem_object`.
+#[repr(transparent)]
+pub struct OpaqueObject<T:
drm::Driver>(Opaque<bindings::drm_gem_object>, PhantomData<T>);
+
+impl<T: drm::Driver> IntoGEMObject for OpaqueObject<T> {
+ unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object)
-> &'a Self {
+ // SAFETY:
+ // - This cast is safe via our type invariant.
+ // - `self_ptr` is guaranteed to be a valid pointer to a gem object by
our safety contract.
+ unsafe { &*self_ptr.cast::<Self>().cast_const() }
+ }
+
+ fn as_raw(&self) -> *mut bindings::drm_gem_object {
+ self.0.get()
+ }
+}
+
+impl<D: drm::Driver> Sealed for OpaqueObject<D> {}
+
pub(super) const fn create_fops() -> bindings::file_operations {
// SAFETY: As by the type invariant, it is safe to initialize
`bindings::file_operations`
// zeroed.
--
2.50.0
Daniel Almeida
2025-Sep-04 13:42 UTC
[PATCH v3 09/14] rust: gem: Introduce DriverObject::Args
> On 29 Aug 2025, at 19:35, Lyude Paul <lyude at redhat.com> wrote: > > This is an associated type that may be used in order to specify a data-type > to pass to gem objects when construction them, allowing for drivers to moreThis doesn?t read very well IMHO.> easily initialize their private-data for gem objects.nit: I think that "private data" doesn?t need a hyphen?> > Signed-off-by: Lyude Paul <lyude at redhat.com> > > --- > V3: > * s/BaseDriverObject/DriverObject/ > > Signed-off-by: Lyude Paul <lyude at redhat.com> > --- > drivers/gpu/drm/nova/gem.rs | 5 ++- > rust/kernel/drm/gem/mod.rs | 75 +++++++++++++++++++++++++++++++++---- > 2 files changed, 71 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs > index 10e3053f1a246..015cb56061a56 100644 > --- a/drivers/gpu/drm/nova/gem.rs > +++ b/drivers/gpu/drm/nova/gem.rs > @@ -19,8 +19,9 @@ pub(crate) struct NovaObject {} > impl gem::DriverObject for NovaObject { > type Driver = NovaDriver; > type Object = gem::Object<Self>; > + type Args = (); > > - fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> { > + fn new(_dev: &NovaDevice, _size: usize, _args: Self::Args) -> impl PinInit<Self, Error> { > try_pin_init!(NovaObject {}) > } > } > @@ -34,7 +35,7 @@ pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self > return Err(EINVAL); > } > > - gem::Object::new(dev, aligned_size) > + gem::Object::new(dev, aligned_size, ()) > } > > /// Look up a GEM object handle for a `File` and return an `ObjectRef` for it. > diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs > index f901d4263ee87..fe6ff3762a504 100644 > --- a/rust/kernel/drm/gem/mod.rs > +++ b/rust/kernel/drm/gem/mod.rs > @@ -6,13 +6,14 @@ > > use crate::{ > alloc::flags::*, > - bindings, drm, > + bindings, > drm::driver::{AllocImpl, AllocOps}, > + drm::{self, private::Sealed}, > error::{to_result, Result}, > prelude::*, > types::{ARef, AlwaysRefCounted, 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. > @@ -21,6 +22,26 @@ > /// [`DriverFile`]: drm::file::DriverFile > pub type DriverFile<T> = drm::File<<<T as DriverObject>::Driver as drm::Driver>::File>; > > +/// A helper macro for implementing AsRef<OpaqueObject<?>> > +macro_rules! impl_as_opaque { > + ($type:ty where $tparam:ident : $tparam_trait:ident) => { > + impl<D, $tparam> core::convert::AsRef<kernel::drm::gem::OpaqueObject<D>> for $type > + where > + D: kernel::drm::driver::Driver, > + Self: kernel::drm::gem::DriverObject<Driver = D>, > + Self: kernel::drm::gem::IntoGEMObject, > + $tparam: $tparam_trait, > + { > + fn as_ref(&self) -> &kernel::drm::gem::OpaqueObject<D> { > + // SAFETY: This cast is safe via our type invariant. > + unsafe { &*((self.as_raw().cast_const()).cast()) } > + } > + } > + }; > +} > + > +pub(crate) use impl_as_opaque; > + > /// GEM object functions, which must be implemented by drivers. > pub trait DriverObject: Sync + Send + Sized { > /// Parent `Driver` for this object. > @@ -29,8 +50,15 @@ pub trait DriverObject: Sync + Send + Sized { > /// The GEM object type that will be passed to various callbacks. > type Object: AllocImpl; > > + /// The data type to use for passing arguments to [`BaseDriverObject::new`]. > + type Args; > + > /// 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( > + dev: &drm::Device<Self::Driver>, > + size: usize, > + args: Self::Args, > + ) -> impl PinInit<Self, Error>; > > /// Open a new handle to an existing object, associated with a File. > fn open(_obj: &Self::Object, _file: &DriverFile<Self>) -> Result { > @@ -42,7 +70,7 @@ fn close(_obj: &Self::Object, _file: &DriverFile<Self>) {} > } > > /// Trait that represents a GEM object subtype > -pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted { > +pub trait IntoGEMObject: Sized + Sealed + AlwaysRefCounted { > /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as > /// this owning object is valid. > fn as_raw(&self) -> *mut bindings::drm_gem_object; > @@ -233,11 +261,11 @@ 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>, size: usize, args: T::Args) -> 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), > + data <- T::new(dev, size, args), > // INVARIANT: The drm subsystem guarantees that the `struct drm_device` will live > // as long as the GEM object lives. > dev: dev.into(), > @@ -289,7 +317,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) { > } > } > > -impl<T: DriverObject> super::private::Sealed for Object<T> {} > +impl<T: DriverObject> Sealed for Object<T> {} > > impl<T: DriverObject> Deref for Object<T> { > type Target = T; > @@ -313,6 +341,39 @@ impl<T: DriverObject> AllocImpl for Object<T> { > }; > } > > +impl_as_opaque!(Object<T> where T: DriverObject); > + > +/// A GEM object whose private-data layout is not known. > +/// > +/// Not all GEM objects are created equal, and subsequently drivers may occasionally need to deal > +/// with situations where they are working with a GEM object but have no knowledge of its > +/// private-data layout. > +/// > +/// It may be used just like a normal [`Object`], with the exception that it cannot access > +/// driver-private data. > +/// > +/// # Invariant > +/// > +/// Via `#[repr(transparent)]`, this type is guaranteed to have an identical data layout to > +/// `struct drm_gem_object`. > +#[repr(transparent)] > +pub struct OpaqueObject<T: drm::Driver>(Opaque<bindings::drm_gem_object>, PhantomData<T>);I?m not sure whether this belongs in this patch. I agree with the motivation, but where exactly is this used for now? I don't see it being passed in a callback, for example. The only way to get one would be through as_ref() IIUC, but who would call this and why?> + > +impl<T: drm::Driver> IntoGEMObject for OpaqueObject<T> { > + unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self { > + // SAFETY: > + // - This cast is safe via our type invariant. > + // - `self_ptr` is guaranteed to be a valid pointer to a gem object by our safety contract. > + unsafe { &*self_ptr.cast::<Self>().cast_const() } > + } > + > + fn as_raw(&self) -> *mut bindings::drm_gem_object { > + self.0.get() > + } > +} > + > +impl<D: drm::Driver> Sealed for OpaqueObject<D> {} > + > pub(super) const fn create_fops() -> bindings::file_operations { > // SAFETY: As by the type invariant, it is safe to initialize `bindings::file_operations` > // zeroed. > -- > 2.50.0 >