rust: drm: add driver abstractions

Implement the DRM driver abstractions.

The `Driver` trait provides the interface to the actual driver to fill
in the driver specific data, such as the `DriverInfo`, driver features
and IOCTLs.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250410235546.43736-4-dakr@kernel.org
[ MISC changes
    * remove unnecessary DRM features; make remaining ones crate private
    * add #[expect(unused)] to avoid warnings
    * add sealed trait
    * remove shmem::Object references
    * original source archive: https://archive.is/Pl9ys

  - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

2 files changed, 121 insertions, 0 deletions

diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
new file mode 100644
index 000000000000..c85cf5e4cd7c
--- /dev/null
+++ b/rust/kernel/drm/driver.rs
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! DRM driver core.
+//!
+//! C header: [`include/linux/drm/drm_drv.h`](srctree/include/linux/drm/drm_drv.h)
+
+use crate::{bindings, drm, str::CStr};
+use macros::vtable;
+
+/// Driver use the GEM memory manager. This should be set for all modern drivers.
+#[expect(unused)]
+pub(crate) const FEAT_GEM: u32 = bindings::drm_driver_feature_DRIVER_GEM;
+
+/// Information data for a DRM Driver.
+pub struct DriverInfo {
+    /// Driver major version.
+    pub major: i32,
+    /// Driver minor version.
+    pub minor: i32,
+    /// Driver patchlevel version.
+    pub patchlevel: i32,
+    /// Driver name.
+    pub name: &'static CStr,
+    /// Driver description.
+    pub desc: &'static CStr,
+}
+
+/// Internal memory management operation set, normally created by memory managers (e.g. GEM).
+pub struct AllocOps {
+    #[expect(unused)]
+    pub(crate) gem_create_object: Option<
+        unsafe extern "C" fn(
+            dev: *mut bindings::drm_device,
+            size: usize,
+        ) -> *mut bindings::drm_gem_object,
+    >,
+    #[expect(unused)]
+    pub(crate) prime_handle_to_fd: Option<
+        unsafe extern "C" fn(
+            dev: *mut bindings::drm_device,
+            file_priv: *mut bindings::drm_file,
+            handle: u32,
+            flags: u32,
+            prime_fd: *mut core::ffi::c_int,
+        ) -> core::ffi::c_int,
+    >,
+    #[expect(unused)]
+    pub(crate) prime_fd_to_handle: Option<
+        unsafe extern "C" fn(
+            dev: *mut bindings::drm_device,
+            file_priv: *mut bindings::drm_file,
+            prime_fd: core::ffi::c_int,
+            handle: *mut u32,
+        ) -> core::ffi::c_int,
+    >,
+    #[expect(unused)]
+    pub(crate) gem_prime_import: Option<
+        unsafe extern "C" fn(
+            dev: *mut bindings::drm_device,
+            dma_buf: *mut bindings::dma_buf,
+        ) -> *mut bindings::drm_gem_object,
+    >,
+    #[expect(unused)]
+    pub(crate) gem_prime_import_sg_table: Option<
+        unsafe extern "C" fn(
+            dev: *mut bindings::drm_device,
+            attach: *mut bindings::dma_buf_attachment,
+            sgt: *mut bindings::sg_table,
+        ) -> *mut bindings::drm_gem_object,
+    >,
+    #[expect(unused)]
+    pub(crate) dumb_create: Option<
+        unsafe extern "C" fn(
+            file_priv: *mut bindings::drm_file,
+            dev: *mut bindings::drm_device,
+            args: *mut bindings::drm_mode_create_dumb,
+        ) -> core::ffi::c_int,
+    >,
+    #[expect(unused)]
+    pub(crate) dumb_map_offset: Option<
+        unsafe extern "C" fn(
+            file_priv: *mut bindings::drm_file,
+            dev: *mut bindings::drm_device,
+            handle: u32,
+            offset: *mut u64,
+        ) -> core::ffi::c_int,
+    >,
+}
+
+/// Trait for memory manager implementations. Implemented internally.
+pub trait AllocImpl: super::private::Sealed {
+    /// The C callback operations for this memory manager.
+    const ALLOC_OPS: AllocOps;
+}
+
+/// The DRM `Driver` trait.
+///
+/// This trait must be implemented by drivers in order to create a `struct drm_device` and `struct
+/// drm_driver` to be registered in the DRM subsystem.
+#[vtable]
+pub trait Driver {
+    /// Context data associated with the DRM driver
+    type Data: Sync + Send;
+
+    /// The type used to manage memory for this driver.
+    type Object: AllocImpl;
+
+    /// Driver metadata
+    const INFO: DriverInfo;
+
+    /// IOCTL list. See `kernel::drm::ioctl::declare_drm_ioctls!{}`.
+    const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor];
+}
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index 9ec6d7cbcaf3..2e3f9a8a9353 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -2,4 +2,12 @@
 
 //! DRM subsystem abstractions.
 
+pub mod driver;
 pub mod ioctl;
+
+pub use self::driver::Driver;
+pub use self::driver::DriverInfo;
+
+pub(crate) mod private {
+    pub trait Sealed {}
+}