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 >