Re: [PATCH 1/6] rust: drm: Add Driver::ParentDevice associated type

[lyude@redhat.com]

Reviewed-by: Lyude Paul <lyude@redhat.com>

On Thu, 2026-05-07 at 00:05 +0200, Danilo Krummrich wrote:
> Add a ParentDevice associated type to the Driver trait, allowing each
> DRM driver to declare its parent bus device type (e.g.
> auxiliary::Device, platform::Device).
> 
> Change UnregisteredDevice::new() to take &T::ParentDevice<Bound>,
> ensuring at the type level that the DRM device's parent matches the
> declared bus device type.
> 
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  drivers/gpu/drm/nova/driver.rs | 8 ++++++--
>  drivers/gpu/drm/tyr/driver.rs  | 6 ++++--
>  rust/kernel/drm/device.rs      | 7 +++++--
>  rust/kernel/drm/driver.rs      | 3 +++
>  4 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nova/driver.rs
> b/drivers/gpu/drm/nova/driver.rs
> index 9eef28b506bb..9d4100f01ea7 100644
> --- a/drivers/gpu/drm/nova/driver.rs
> +++ b/drivers/gpu/drm/nova/driver.rs
> @@ -2,7 +2,10 @@
>  
>  use kernel::{
>      auxiliary,
> -    device::Core,
> +    device::{
> +        Core,
> +        DeviceContext, //
> +    },
>      drm::{
>          self,
>          gem,
> @@ -59,7 +62,7 @@ fn probe(
>      ) -> impl PinInit<Self, Error> + 'bound {
>          let data = try_pin_init!(NovaData { adev: adev.into() });
>  
> -        let drm =
> drm::UnregisteredDevice::<Self>::new(adev.as_ref(), data)?;
> +        let drm = drm::UnregisteredDevice::<Self>::new(adev, data)?;
>          let drm = drm::Registration::new_foreign_owned(drm,
> adev.as_ref(), 0)?;
>  
>          Ok(Self { drm: drm.into() })
> @@ -71,6 +74,7 @@ impl drm::Driver for NovaDriver {
>      type Data = NovaData;
>      type File = File;
>      type Object<Ctx: drm::DeviceContext> = gem::Object<NovaObject,
> Ctx>;
> +    type ParentDevice<Ctx: DeviceContext> = auxiliary::Device<Ctx>;
>  
>      const INFO: drm::DriverInfo = INFO;
>  
> diff --git a/drivers/gpu/drm/tyr/driver.rs
> b/drivers/gpu/drm/tyr/driver.rs
> index 2743178af325..747745d23f31 100644
> --- a/drivers/gpu/drm/tyr/driver.rs
> +++ b/drivers/gpu/drm/tyr/driver.rs
> @@ -8,7 +8,8 @@
>      device::{
>          Bound,
>          Core,
> -        Device, //
> +        Device,
> +        DeviceContext, //
>      },
>      drm,
>      drm::ioctl,
> @@ -131,7 +132,7 @@ fn probe(
>                  gpu_info,
>          });
>  
> -        let tdev =
> drm::UnregisteredDevice::<TyrDrmDriver>::new(pdev.as_ref(), data)?;
> +        let tdev =
> drm::UnregisteredDevice::<TyrDrmDriver>::new(pdev, data)?;
>          let tdev =
> drm::driver::Registration::new_foreign_owned(tdev, pdev.as_ref(),
> 0)?;
>  
>          let driver = TyrPlatformDriverData {
> @@ -176,6 +177,7 @@ impl drm::Driver for TyrDrmDriver {
>      type Data = TyrDrmDeviceData;
>      type File = TyrDrmFileData;
>      type Object<R: drm::DeviceContext> = drm::gem::Object<TyrObject,
> R>;
> +    type ParentDevice<Ctx: DeviceContext> = platform::Device<Ctx>;
>  
>      const INFO: drm::DriverInfo = INFO;
>  
> diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
> index d91f19dcc375..492c2f2c7ca4 100644
> --- a/rust/kernel/drm/device.rs
> +++ b/rust/kernel/drm/device.rs
> @@ -197,7 +197,10 @@ impl<T: drm::Driver> UnregisteredDevice<T> {
>      /// Create a new `UnregisteredDevice` for a `drm::Driver`.
>      ///
>      /// This can be used to create a
> [`Registration`](kernel::drm::Registration).
> -    pub fn new(dev: &device::Device, data: impl PinInit<T::Data,
> Error>) -> Result<Self> {
> +    pub fn new(
> +        dev: &T::ParentDevice<device::Bound>,
> +        data: impl PinInit<T::Data, Error>,
> +    ) -> Result<Self> {
>          // `__drm_dev_alloc` uses `kmalloc()` to allocate memory,
> hence ensure a `kmalloc()`
>          // compatible `Layout`.
>          let layout = Kmalloc::aligned_layout(Layout::new::<Device<T,
> Uninit>>());
> @@ -207,7 +210,7 @@ pub fn new(dev: &device::Device, data: impl
> PinInit<T::Data, Error>) -> Result<S
>          // - `dev` is valid by its type invarants,
>          let raw_drm: *mut Device<T, Uninit> = unsafe {
>              bindings::__drm_dev_alloc(
> -                dev.as_raw(),
> +                dev.as_ref().as_raw(),
>                  &Self::VTABLE,
>                  layout.size(),
>                  mem::offset_of!(Device<T, Uninit>, dev),
> diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
> index 294e17af86a3..9d06f8c5b2da 100644
> --- a/rust/kernel/drm/driver.rs
> +++ b/rust/kernel/drm/driver.rs
> @@ -114,6 +114,9 @@ pub trait Driver {
>      /// The type used to represent a DRM File (client)
>      type File: drm::file::DriverFile;
>  
> +    /// The bus device type of the parent device that the DRM device
> is associated with.
> +    type ParentDevice<Ctx: device::DeviceContext>:
> device::AsBusDevice<Ctx>;
> +
>      /// Driver metadata
>      const INFO: DriverInfo;
>