On Thu, 2026-01-22 at 22:56 -0300, Daniel Almeida wrote:
> > }
> > }
> > diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
> > index 0e81957cf8c28..4c03105e6a817 100644
> > --- a/rust/kernel/drm/device.rs
> > +++ b/rust/kernel/drm/device.rs
> > @@ -163,13 +163,13 @@ impl<T: drm::Driver> UnregisteredDevice<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:
> > T::Object::<Uninit>::ALLOC_OPS.gem_create_object,
> > + prime_handle_to_fd:
> > T::Object::<Uninit>::ALLOC_OPS.prime_handle_to_fd,
> > + prime_fd_to_handle:
> > T::Object::<Uninit>::ALLOC_OPS.prime_fd_to_handle,
> > + gem_prime_import:
> > T::Object::<Uninit>::ALLOC_OPS.gem_prime_import,
> > + gem_prime_import_sg_table:
> > T::Object::<Uninit>::ALLOC_OPS.gem_prime_import_sg_table,
> > + dumb_create: T::Object::<Uninit>::ALLOC_OPS.dumb_create,
> > + dumb_map_offset:
> > T::Object::<Uninit>::ALLOC_OPS.dumb_map_offset,
>
> Why are we specifically going with Uninit here?
I think this was just an assumption that similarly to KMS callbacks,
gem callbacks can also happen before registration. except, that some of
these clearly can't happen before registration - whoops.
But this being said - it doesn't really make any difference what the
DeviceContext is here. The DeviceContext generic here isn't actually
used in any way, nor is it used by the C callback, it's just here
because we have to specify it on the associated type.
>
> > show_fdinfo: None,
> > fbdev_probe: None,
> >
> > diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
> > index a16605b407159..94ebaf19ac069 100644
> > --- a/rust/kernel/drm/driver.rs
> > +++ b/rust/kernel/drm/driver.rs
> > @@ -110,7 +110,7 @@ pub trait Driver {
> > type Data: Sync + Send;
> >
> > /// The type used to manage memory for this driver.
> > - type Object: AllocImpl;
> > + type Object<Ctx: drm::DeviceContext>: AllocImpl;
> >
> > /// 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 b4199945db378..3af9f52f8eda4 100644
> > --- a/rust/kernel/drm/gem/mod.rs
> > +++ b/rust/kernel/drm/gem/mod.rs
> > @@ -8,6 +8,10 @@
> > bindings,
> > drm::{
> > self,
> > + device::{
> > + DeviceContext,
> > + Registered, //
> > + },
> > driver::{
> > AllocImpl,
> > AllocOps, //
> > @@ -22,6 +26,7 @@
> > types::Opaque,
> > };
> > use core::{
> > + marker::PhantomData,
> > ops::Deref,
> > ptr::NonNull, //
> > };
> > @@ -33,21 +38,30 @@
> > /// [`DriverFile`]: drm::file::DriverFile
> > pub type DriverFile<T> = drm::File<<<T as DriverObject>::Driver as
> > drm::Driver>::File>;
> >
> > +/// A type alias for retrieving the current [`AllocImpl`] for a
> > given [`DriverObject`].
> > +///
> > +/// [`Driver`]: drm::Driver
> > +pub type DriverAllocImpl<T, Ctx = Registered> =
> > + <<T as DriverObject>::Driver as drm::Driver>::Object<Ctx>;
>
> Should this be a follow up patch instead?
>
> > +
> > /// GEM object functions, which must be implemented by drivers.
> > pub trait DriverObject: Sync + Send + Sized {
> > /// Parent `Driver` for this object.
> > type Driver: drm::Driver;
> >
> > /// 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<Ctx: DeviceContext>(
> > + dev: &drm::Device<Self::Driver, Ctx>,
> > + 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: &DriverAllocImpl<Self>, _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: &DriverAllocImpl<Self>, _file:
> > &DriverFile<Self>) {}
> > }
> >
> > /// Trait that represents a GEM object subtype
> > @@ -73,9 +87,12 @@ extern "C" fn open_callback<T: DriverObject>(
> > // SAFETY: `open_callback` is only ever called with a valid
> > pointer to a `struct drm_file`.
> > let file = unsafe { DriverFile::<T>::from_raw(raw_file) };
> >
> > - // 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>::from_raw(raw_obj) };
> > + // SAFETY:
> > + // * `open_callback` is specified in the AllocOps structure
> > for `DriverObject`, ensuring that
> > + // `raw_obj` is contained within a `DriverAllocImpl<T>`
> > + // * It is only possible for `open_callback` to be called
> > after device registration, ensuring
> > + // that the object's device is in the `Registered` state.
> > + let obj: &DriverAllocImpl<T> = unsafe {
> > IntoGEMObject::from_raw(raw_obj) };
> >
> > match T::open(obj, file) {
> > Err(e) => e.to_errno(),
> > @@ -92,12 +109,12 @@ extern "C" fn close_callback<T: DriverObject>(
> >
> > // 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>::from_raw(raw_obj) };
> > + let obj: &DriverAllocImpl<T> = unsafe {
> > IntoGEMObject::from_raw(raw_obj) };
> >
> > T::close(obj, file);
> > }
> >
> > -impl<T: DriverObject> IntoGEMObject for Object<T> {
> > +impl<T: DriverObject, Ctx: DeviceContext> IntoGEMObject for
> > Object<T, Ctx> {
> > fn as_raw(&self) -> *mut bindings::drm_gem_object {
> > self.obj.get()
> > }
> > @@ -105,7 +122,7 @@ fn as_raw(&self) -> *mut
> > bindings::drm_gem_object {
> > unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object)
> > -> &'a Self {
> > // SAFETY: `obj` is guaranteed to be in an `Object<T>` via
> > the safety contract of this
> > // function
> > - unsafe {
> > &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T>, obj)
> > }
> > + unsafe {
> > &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T, Ctx>,
> > obj) }
> > }
> > }
> >
> > @@ -122,7 +139,7 @@ fn size(&self) -> usize {
> > fn create_handle<D, F>(&self, file: &drm::File<F>) ->
> > Result<u32>
> > where
> > Self: AllocImpl<Driver = D>,
> > - D: drm::Driver<Object = Self, File = F>,
> > + D: drm::Driver<Object<Registered> = Self, File = F>,
> > F: drm::file::DriverFile<Driver = D>,
> > {
> > let mut handle: u32 = 0;
> > @@ -137,7 +154,7 @@ fn create_handle<D, F>(&self, file:
> > &drm::File<F>) -> Result<u32>
> > fn lookup_handle<D, F>(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<Registered> = Self, File = F>,
> > F: drm::file::DriverFile<Driver = D>,
> > {
> > // SAFETY: The arguments are all valid per the type
> > invariants.
> > @@ -177,16 +194,18 @@ impl<T: IntoGEMObject> BaseObject for T {}
> > ///
> > /// # Invariants
> > ///
> > -/// - `self.obj` is a valid instance of a `struct drm_gem_object`.
> > +/// * `self.obj` is a valid instance of a `struct drm_gem_object`.
> > +/// * Any type invariants of `Ctx` apply to the parent DRM device
> > for this GEM object.
> > #[repr(C)]
> > #[pin_data]
> > -pub struct Object<T: DriverObject + Send + Sync> {
> > +pub struct Object<T: DriverObject + Send + Sync, Ctx:
> > DeviceContext = Registered> {
> > obj: Opaque<bindings::drm_gem_object>,
> > #[pin]
> > data: T,
> > + _ctx: PhantomData<Ctx>,
> > }
> >
> > -impl<T: DriverObject> Object<T> {
> > +impl<T: DriverObject, Ctx: DeviceContext> Object<T, Ctx> {
> > const OBJECT_FUNCS: bindings::drm_gem_object_funcs =
> > bindings::drm_gem_object_funcs {
> > free: Some(Self::free_callback),
> > open: Some(open_callback::<T>),
> > @@ -206,11 +225,12 @@ 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, Ctx>, size: usize) ->
> > 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),
> > + _ctx: PhantomData,
> > }),
> > GFP_KERNEL,
> > )?;
> > @@ -219,6 +239,8 @@ pub fn new(dev: &drm::Device<T::Driver>, size:
> > usize) -> Result<ARef<Self>> {
> > unsafe { (*obj.as_raw()).funcs = &Self::OBJECT_FUNCS };
> >
> > // SAFETY: The arguments are all valid per the type
> > invariants.
> > + // INVARIANT: We use `dev` for creating the GEM object,
> > which is known to be in state `Ctx` -
> > + // ensuring that the GEM object's pointer to the DRM
> > device is always in the same state.
> > to_result(unsafe {
> > bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size)
> > })?;
> >
> > // SAFETY: We will never move out of `Self` as `ARef<Self>`
> > is always treated as pinned.
> > @@ -232,13 +254,15 @@ pub fn new(dev: &drm::Device<T::Driver>,
> > size: usize) -> Result<ARef<Self>> {
> > }
> >
> > /// Returns the `Device` that owns this GEM object.
> > - pub fn dev(&self) -> &drm::Device<T::Driver> {
> > + pub fn dev(&self) -> &drm::Device<T::Driver, Ctx> {
> > // SAFETY:
> > // - `struct drm_gem_object.dev` is initialized and valid
> > for as long as the GEM
> > // object lives.
> > // - The device we used for creating the gem object is
> > passed as &drm::Device<T::Driver> to
> > // Object::<T>::new(), so we know that `T::Driver` is the
> > right generic parameter to use
> > // here.
> > + // - Any type invariants of `Ctx` are upheld by using the
> > same `Ctx` for the `Device` we
> > + // return.
> > unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
> > }
> >
> > @@ -264,7 +288,7 @@ extern "C" fn free_callback(obj: *mut
> > bindings::drm_gem_object) {
> > }
> >
> > // SAFETY: Instances of `Object<T>` are always reference-counted.
> > -unsafe impl<T: DriverObject> crate::sync::aref::AlwaysRefCounted
> > for Object<T> {
> > +unsafe impl<T: DriverObject, Ctx: DeviceContext> AlwaysRefCounted
> > for Object<T, Ctx> {
> > fn inc_ref(&self) {
> > // SAFETY: The existence of a shared reference guarantees
> > that the refcount is non-zero.
> > unsafe { bindings::drm_gem_object_get(self.as_raw()) };
> > @@ -279,9 +303,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
> > }
> > }
> >
> > -impl<T: DriverObject> super::private::Sealed for Object<T> {}
> > +impl<T: DriverObject, Ctx: DeviceContext> super::private::Sealed
> > for Object<T, Ctx> {}
> >
> > -impl<T: DriverObject> Deref for Object<T> {
> > +impl<T: DriverObject, Ctx: DeviceContext> Deref for Object<T, Ctx>
> > {
> > type Target = T;
> >
> > fn deref(&self) -> &Self::Target {
> > @@ -289,7 +313,7 @@ fn deref(&self) -> &Self::Target {
> > }
> > }
> >
> > -impl<T: DriverObject> AllocImpl for Object<T> {
> > +impl<T: DriverObject, Ctx: DeviceContext> AllocImpl for Object<T,
> > Ctx> {
> > type Driver = T::Driver;
> >
> > const ALLOC_OPS: AllocOps = AllocOps {
> > --
> > 2.52.0
> >
> >
