linux.git/rust/kernel/drm/mod.rs, branch v7.2-rc1

rust/drm: Introduce DeviceContext

2026-06-02T19:35:25+00:00

One of the tricky things about DRM bindings in Rust is the fact that
initialization of a DRM device is a multi-step process. It's quite normal
for a device driver to start making use of its DRM device for tasks like
creating GEM objects before userspace registration happens. This is an
issue in rust though, since prior to userspace registration the device is
only partly initialized. This means there's a plethora of DRM device
operations we can't yet expose without opening up the door to UB if the DRM
device in question isn't yet registered.

Additionally, this isn't something we can reliably check at runtime. And
even if we could, performing an operation which requires the device be
registered when the device isn't actually registered is a programmer bug,
meaning there's no real way to gracefully handle such a mistake at runtime.
And even if that wasn't the case, it would be horrendously annoying and
noisy to have to check if a device is registered constantly throughout a
driver.

In order to solve this, we first take inspiration from
`kernel::device::DeviceContext` and introduce `kernel::drm::DeviceContext`.
This provides us with a ZST type that we can generalize over to represent
contexts where a device is known to have been registered with userspace at
some point in time (`Registered`), along with contexts where we can't make
such a guarantee (`Uninit`).

It's important to note we intentionally do not provide a `DeviceContext`
which represents an unregistered device. This is because there's no
reasonable way to guarantee that a device with long-living references to
itself will not be registered eventually with userspace. Instead, we
provide a new-type for this: `UnregisteredDevice` which can
provide a guarantee that the `Device` has never been registered with
userspace. To ensure this, we modify `Registration` so that creating a new
`Registration` requires passing ownership of an `UnregisteredDevice`.

Signed-off-by: Lyude Paul 
Reviewed-by: Daniel Almeida 
Link: https://patch.msgid.link/20260507220044.3204919-2-lyude@redhat.com
Signed-off-by: Danilo Krummrich

rust: drm: add base GPUVM immediate mode abstraction

2026-05-05T10:52:49+00:00

Add a GPUVM abstraction to be used by Rust GPU drivers.

GPUVM keeps track of a GPU's virtual address (VA) space and manages the
corresponding virtual mappings represented by "GPU VA" objects. It also
keeps track of the gem::Object used to back the mappings through
GpuVmBo.

This abstraction is only usable by drivers that wish to use GPUVM in
immediate mode. This allows us to build the locking scheme into the API
design. It means that the GEM mutex is used for the GEM gpuva list, and
that the resv lock is used for the extobj list. The evicted list is not
yet used in this version.

This abstraction provides a special handle called the UniqueRefGpuVm,
which is a wrapper around ARef that provides access to the
interval tree. Generally, all changes to the address space requires
mutable access to this unique handle.

Signed-off-by: Asahi Lina 
Co-developed-by: Daniel Almeida 
Signed-off-by: Daniel Almeida 
Reviewed-by: Daniel Almeida 
Co-developed-by: Alice Ryhl 
Signed-off-by: Alice Ryhl 
Link: https://patch.msgid.link/20260409-gpuvm-rust-v6-1-b16e6ada7261@google.com
Signed-off-by: Danilo Krummrich

rust: drm: gem: Add GEM object abstraction

2025-04-28T08:08:23+00:00

DRM GEM is the DRM memory management subsystem used by most modern
drivers; add a Rust abstraction for DRM GEM.

This includes the BaseObject trait, which contains operations shared by
all GEM object classes.

Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
Link: https://lore.kernel.org/r/20250410235546.43736-8-dakr@kernel.org
[ Rework of GEM object abstractions
    * switch to the Opaque type
    * fix (mutable) references to struct drm_gem_object (which in this
      context is UB)
    * drop all custom reference types in favor of AlwaysRefCounted
    * bunch of minor changes and simplifications (e.g. IntoGEMObject
      trait)
    * write and fix safety and invariant comments
    * remove necessity for and convert 'as' casts
    * original source archive: https://archive.is/dD5SL

  - Danilo ]
[ Fix missing CONFIG_DRM guards in rust/helpers/drm.c. - Danilo ]
Signed-off-by: Danilo Krummrich

rust: drm: file: Add File abstraction

2025-04-24T12:11:58+00:00

A DRM File is the DRM counterpart to a kernel file structure,
representing an open DRM file descriptor.

Add a Rust abstraction to allow drivers to implement their own File types
that implement the DriverFile trait.

Reviewed-by: Maxime Ripard 
Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
Link: https://lore.kernel.org/r/20250410235546.43736-7-dakr@kernel.org
[ Rework of drm::File
    * switch to the Opaque type
    * fix (mutable) references to struct drm_file (which in this context
      is UB)
    * restructure and rename functions to align with common kernel
      schemes
    * write and fix safety and invariant comments
    * remove necessity for and convert 'as' casts
    * original source archive: https://archive.is/GH8oy

  - Danilo ]
Signed-off-by: Danilo Krummrich

rust: drm: add DRM driver registration

2025-04-24T12:00:13+00:00

Implement the DRM driver `Registration`.

The `Registration` structure is responsible to register and unregister a
DRM driver. It makes use of the `Devres` container in order to allow the
`Registration` to be owned by devres, such that it is automatically
dropped (and the DRM driver unregistered) once the parent device is
unbound.

Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
Link: https://lore.kernel.org/r/20250410235546.43736-6-dakr@kernel.org
[ Rework of drm::Registration
    * move VTABLE to drm::Device to prevent use-after-free bugs; VTABLE
      needs to be bound to the lifetime of drm::Device, not the
      drm::Registration
    * combine new() and register() to get rid of the registered boolean
    * remove file_operations
    * move struct drm_device creation to drm::Device
    * introduce Devres
    * original source archive: https://archive.is/Pl9ys

  - Danilo ]
Signed-off-by: Danilo Krummrich

rust: drm: add device abstraction

2025-04-24T12:00:10+00:00

Implement the abstraction for a `struct drm_device`.

A `drm::Device` creates a static const `struct drm_driver` filled with
the data from the `drm::Driver` trait implementation of the actual
driver creating the `drm::Device`.

Reviewed-by: Maxime Ripard 
Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
Link: https://lore.kernel.org/r/20250410235546.43736-5-dakr@kernel.org
[ Rewrite of drm::Device
    * full rewrite of the drm::Device abstraction using the subclassing
      pattern
    * original source archive: http://archive.today/5NxBo

  - Danilo ]
Signed-off-by: Danilo Krummrich

rust: drm: add driver abstractions

2025-04-24T11:50:10+00:00

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 
Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
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

rust: drm: ioctl: Add DRM ioctl abstraction

2025-04-24T11:50:05+00:00

DRM drivers need to be able to declare which driver-specific ioctls they
support. Add an abstraction implementing the required types and a helper
macro to generate the ioctl definition inside the DRM driver.

Note that this macro is not usable until further bits of the abstraction
are in place (but it will not fail to compile on its own, if not called).

Signed-off-by: Asahi Lina 
Reviewed-by: Alyssa Rosenzweig 
Reviewed-by: Lyude Paul 
Link: https://lore.kernel.org/r/20250410235546.43736-3-dakr@kernel.org
[ MISC fixes
    * wrap raw_data in Opaque to avoid UB when creating a reference
    * fix IOCTL sample declaration
    * fix safety comment of IOCTL argument
    * original source archive: https://archive.is/LqHDQ

  - Danilo ]
Signed-off-by: Danilo Krummrich