* [PATCH v3 1/23] rust: drm: kms: adapt Lyude's KMS series to current DRM APIs
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 2/23] rust: drm: kms: tie mode-object references to their owners Mike Lothian
` (21 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, David Airlie, Simona Vetter,
Lyude Paul, Asahi Lina, Mukesh Kumar Chaurasiya (IBM),
rust-for-linux, linux-kernel
Adapt the Rust KMS bindings to the current DRM APIs while preserving
Lyude Paul's implementation as a separate, unchanged series.
Update the atomic state type to drm_atomic_commit, initialize the
current callback-table fields, remove the retired CRTC helper field,
and use the current Rust ARef path and helper annotations. Keep
callback vtables in static storage so every reference handed to DRM
core remains valid for the device lifetime.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/helpers/drm/atomic.c | 21 ++++++++--------
rust/kernel/drm/gem/shmem.rs | 1 +
rust/kernel/drm/kms.rs | 26 +++++++++++---------
rust/kernel/drm/kms/atomic.rs | 41 ++++++++++++++++----------------
rust/kernel/drm/kms/connector.rs | 2 ++
rust/kernel/drm/kms/crtc.rs | 21 +++++++++-------
rust/kernel/drm/kms/plane.rs | 10 ++++----
7 files changed, 68 insertions(+), 54 deletions(-)
diff --git a/rust/helpers/drm/atomic.c b/rust/helpers/drm/atomic.c
index fff70053f694..420d72745e6b 100644
--- a/rust/helpers/drm/atomic.c
+++ b/rust/helpers/drm/atomic.c
@@ -2,23 +2,24 @@
#include <drm/drm_atomic.h>
-void rust_helper_drm_atomic_state_get(struct drm_atomic_state *state)
+__rust_helper void rust_helper_drm_atomic_commit_get(struct drm_atomic_commit *state)
{
- drm_atomic_state_get(state);
+ drm_atomic_commit_get(state);
}
-void rust_helper_drm_atomic_state_put(struct drm_atomic_state *state)
+__rust_helper void rust_helper_drm_atomic_commit_put(struct drm_atomic_commit *state)
{
- drm_atomic_state_put(state);
+ drm_atomic_commit_put(state);
}
// Macros for generating one repetitive atomic state accessors (like drm_atomic_get_new_plane_state)
-#define STATE_FUNC(type, tense) \
- struct drm_ ## type ## _state *rust_helper_drm_atomic_get_ ## tense ## _ ## type ## _state( \
- const struct drm_atomic_state *state, \
- struct drm_ ## type *type \
- ) { \
- return drm_atomic_get_## tense ## _ ## type ## _state(state, type); \
+#define STATE_FUNC(type, tense) \
+ __rust_helper struct drm_ ## type ## _state * \
+ rust_helper_drm_atomic_get_ ## tense ## _ ## type ## _state( \
+ const struct drm_atomic_commit *state, \
+ struct drm_ ## type *type) \
+ { \
+ return drm_atomic_get_## tense ## _ ## type ## _state(state, type); \
}
#define STATE_FUNCS(type) \
STATE_FUNC(type, new); \
diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs
index 593fc0d427e4..86797ab39ffd 100644
--- a/rust/kernel/drm/gem/shmem.rs
+++ b/rust/kernel/drm/gem/shmem.rs
@@ -636,6 +636,7 @@ impl drm::Driver for KunitDriver {
type File = KunitFile;
type Object = Object<KunitObject>;
type ParentDevice<Ctx: device::DeviceContext> = faux::Device<Ctx>;
+ type Kms = core::marker::PhantomData<Self>;
const INFO: drm::DriverInfo = INFO;
const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor] = &[];
diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
index 820b0df265ff..8baf9c2906f5 100644
--- a/rust/kernel/drm/kms.rs
+++ b/rust/kernel/drm/kms.rs
@@ -16,8 +16,11 @@
drm::{device::Device, driver::Driver, private::Sealed},
error::to_result,
prelude::*,
- sync::{Mutex, MutexGuard},
- types::*,
+ sync::{
+ aref::{ARef, AlwaysRefCounted},
+ Mutex,
+ MutexGuard, //
+ },
};
use bindings;
use core::{
@@ -52,7 +55,7 @@ pub trait KmsImpl {
type Driver: Driver;
/// The optional KMS callback operations for this driver.
- const MODE_CONFIG_OPS: Option<ModeConfigOps>;
+ const MODE_CONFIG_OPS: Option<&'static ModeConfigOps>;
/// The callback for setting up KMS on a device
///
@@ -216,14 +219,14 @@ pub trait KmsDriver: Driver {
/// implementations.
///
/// [`DriverConnector`]: connector::DriverConnector
- type Connector: connector::DriverConnector;
+ type Connector: connector::DriverConnector<Driver = Self>;
/// The driver's [`DriverPlane`] implementation.
///
/// TODO: This will be unneeded in the future once we support multiple [`DriverPlane`]
/// implementations.
///
- type Plane: plane::DriverPlane;
+ type Plane: plane::DriverPlane<Driver = Self>;
/// The driver's [`DriverCrtc`] implementation.
///
@@ -231,7 +234,7 @@ pub trait KmsDriver: Driver {
/// implementations.
///
/// [`DriverCrtc`]: crtc::DriverCrtc
- type Crtc: crtc::DriverCrtc;
+ type Crtc: crtc::DriverCrtc<Driver = Self>;
/// The driver's [`DriverEncoder`] implementation.
///
@@ -239,7 +242,7 @@ pub trait KmsDriver: Driver {
/// implementations.
///
/// [`DriverEncoder`]: encoder::DriverEncoder
- type Encoder: encoder::DriverEncoder;
+ type Encoder: encoder::DriverEncoder<Driver = Self>;
/// Return a [`ModeConfigInfo`] structure for this [`device::Device`].
fn mode_config_info(
@@ -279,7 +282,7 @@ fn atomic_commit_tail<'a>(
impl<T: KmsDriver> private::KmsImpl for T {
type Driver = Self;
- const MODE_CONFIG_OPS: Option<ModeConfigOps> = Some(ModeConfigOps {
+ const MODE_CONFIG_OPS: Option<&'static ModeConfigOps> = Some(&ModeConfigOps {
kms_vtable: bindings::drm_mode_config_funcs {
atomic_check: Some(bindings::drm_atomic_helper_check),
fb_create: Some(bindings::drm_gem_fb_create),
@@ -305,7 +308,7 @@ unsafe fn setup_kms(drm: &Device<Self::Driver>) -> Result<ModeConfigInfo> {
let mode_config_info = T::mode_config_info(drm.as_ref().as_ref(), drm)?;
// SAFETY: `MODE_CONFIG_OPS` is always Some() in this implementation
- let ops = unsafe { T::MODE_CONFIG_OPS.as_ref().unwrap_unchecked() };
+ let ops = unsafe { T::MODE_CONFIG_OPS.unwrap_unchecked() };
// SAFETY:
// - This function can only be called before registration via our safety contract.
@@ -352,7 +355,7 @@ impl<T: KmsDriver> KmsImpl for T {}
impl<T: Driver> private::KmsImpl for PhantomData<T> {
type Driver = T;
- const MODE_CONFIG_OPS: Option<ModeConfigOps> = None;
+ const MODE_CONFIG_OPS: Option<&'static ModeConfigOps> = None;
}
impl<T: Driver> KmsImpl for PhantomData<T> {}
@@ -501,7 +504,7 @@ macro_rules! impl_aref_for_mode_object {
(impl $( < $( $param:ident: $bound:ident ),+ > )? for $type:ty) => {
// SAFETY: drm_mode_object_get()/put() ensure the type is ref-counted according to the
// safety contract
- unsafe impl $( < $( $param: $bound ),+ > )? kernel::types::AlwaysRefCounted for $type {
+ unsafe impl $( < $( $param: $bound ),+ > )? kernel::sync::aref::AlwaysRefCounted for $type {
#[inline]
fn inc_ref(&self) {
// SAFETY: We're guaranteed by the safety contract of `ModeObject` that
@@ -535,6 +538,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
///
/// `ModeObjectVtable::vtable()` must always return a valid pointer to the relevant mode object's
/// vtable.
+#[allow(dead_code)]
pub(crate) unsafe trait ModeObjectVtable {
/// The type for the auto-generated vtable.
type Vtable;
diff --git a/rust/kernel/drm/kms/atomic.rs b/rust/kernel/drm/kms/atomic.rs
index cc14bff47abd..18dc136940f3 100644
--- a/rust/kernel/drm/kms/atomic.rs
+++ b/rust/kernel/drm/kms/atomic.rs
@@ -1,31 +1,32 @@
// SPDX-License-Identifier: GPL-2.0 OR MIT
-//! [`struct drm_atomic_state`] related bindings for rust.
+//! [`struct drm_atomic_commit`] related bindings for rust.
//!
-//! [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+//! [`struct drm_atomic_commit`]: srctree/include/drm/drm_atomic.h
use super::{connector::*, crtc::*, plane::*, KmsDriver, ModeObject};
use crate::{
bindings,
drm::device::Device,
error::{from_err_ptr, to_result},
prelude::*,
+ sync::aref::{ARef, AlwaysRefCounted},
types::*,
};
use core::{cell::Cell, marker::*, mem::ManuallyDrop, ops::*, ptr::NonNull};
-/// The main wrapper around [`struct drm_atomic_state`].
+/// The main wrapper around [`struct drm_atomic_commit`].
///
/// This type is usually embedded within another interface such as an [`AtomicStateMutator`].
///
/// # Invariants
///
-/// - The data layout of this type is identical to [`struct drm_atomic_state`].
+/// - The data layout of this type is identical to [`struct drm_atomic_commit`].
/// - `state` is initialized for as long as this type is exposed to users.
///
-/// [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+/// [`struct drm_atomic_commit`]: srctree/include/drm/drm_atomic.h
#[repr(transparent)]
pub struct AtomicState<T: KmsDriver> {
- pub(super) state: Opaque<bindings::drm_atomic_state>,
+ pub(super) state: Opaque<bindings::drm_atomic_commit>,
_p: PhantomData<T>,
}
@@ -34,18 +35,18 @@ impl<T: KmsDriver> AtomicState<T> {
///
/// # Safety
///
- /// `ptr` must point to a valid initialized instance of [`struct drm_atomic_state`].
+ /// `ptr` must point to a valid initialized instance of [`struct drm_atomic_commit`].
///
- /// [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+ /// [`struct drm_atomic_commit`]: srctree/include/drm/drm_atomic.h
#[allow(dead_code)]
- pub(super) unsafe fn from_raw<'a>(ptr: *const bindings::drm_atomic_state) -> &'a Self {
+ pub(super) unsafe fn from_raw<'a>(ptr: *const bindings::drm_atomic_commit) -> &'a Self {
// SAFETY: Our data layout is identical
// INVARIANT: Our safety contract upholds the guarantee that `state` is initialized for as
// long as this type is exposed to users.
unsafe { &*ptr.cast() }
}
- pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_state {
+ pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_commit {
self.state.get()
}
@@ -102,12 +103,12 @@ pub fn get_old_connector_state<C>(&self, connector: &C) -> Option<&C::State>
unsafe impl<T: KmsDriver> AlwaysRefCounted for AtomicState<T> {
fn inc_ref(&self) {
// SAFETY: `state` is initialized for as long as this type is exposed to users
- unsafe { bindings::drm_atomic_state_get(self.state.get()) }
+ unsafe { bindings::drm_atomic_commit_get(self.state.get()) }
}
unsafe fn dec_ref(obj: NonNull<Self>) {
// SAFETY: `obj` contains a valid non-null pointer to an initialized `Self`.
- unsafe { bindings::drm_atomic_state_put(obj.as_ptr().cast()) }
+ unsafe { bindings::drm_atomic_commit_put(obj.as_ptr().cast()) }
}
}
@@ -141,11 +142,11 @@ impl<T: KmsDriver> AtomicStateMutator<T> {
///
/// # Safety
///
- /// `ptr` must point to a valid `drm_atomic_state`
+ /// `ptr` must point to a valid `drm_atomic_commit`
#[allow(dead_code)]
- pub(super) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
+ pub(super) unsafe fn new(ptr: NonNull<bindings::drm_atomic_commit>) -> Self {
Self {
- // SAFETY: The data layout of `AtomicState<T>` is identical to drm_atomic_state
+ // SAFETY: The data layout of `AtomicState<T>` is identical to drm_atomic_commit
// We use `ManuallyDrop` because `AtomicStateMutator` is only ever provided to users in
// the context of KMS callbacks. As such, skipping ref inc/dec for the atomic state is
// convienent for our bindings.
@@ -156,7 +157,7 @@ pub(super) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
}
}
- pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_state {
+ pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_commit {
self.state.as_raw()
}
@@ -273,8 +274,8 @@ fn drop(&mut self) {
impl<T: KmsDriver> AtomicStateComposer<T> {
/// # Safety
///
- /// The caller guarantees that `ptr` points to a valid instance of `drm_atomic_state`.
- pub(crate) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
+ /// The caller guarantees that `ptr` points to a valid instance of `drm_atomic_commit`.
+ pub(crate) unsafe fn new(ptr: NonNull<bindings::drm_atomic_commit>) -> Self {
// SAFETY: see `AtomicStateMutator::from_raw()`
Self(unsafe { AtomicStateMutator::new(ptr) })
}
@@ -681,11 +682,11 @@ pub fn commit_hw_done<'b>(
// The actual raw C callback for custom atomic commit tail implementations
pub(crate) unsafe extern "C" fn commit_tail_callback<T: KmsDriver>(
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// - We're guaranteed by DRM that `state` always points to a valid instance of
- // `bindings::drm_atomic_state`
+ // `bindings::drm_atomic_commit`
// - This conversion is safe via the type invariants
let state = unsafe { AtomicState::from_raw(state.cast_const()) };
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index f7817c5037bd..78b08b94587b 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -94,6 +94,7 @@ pub trait DriverConnector: Send + Sync + Sized {
/// The generated C vtable for this [`DriverConnector`] implementation
const OPS: &'static DriverConnectorOps = &DriverConnectorOps {
funcs: bindings::drm_connector_funcs {
+ atomic_create_state: None,
dpms: None,
atomic_get_property: None,
atomic_set_property: None,
@@ -110,6 +111,7 @@ pub trait DriverConnector: Send + Sync + Sized {
debugfs_init: None,
oob_hotplug_event: None,
atomic_duplicate_state: Some(atomic_duplicate_state_callback::<Self::State>),
+ color_format: None,
},
helper_funcs: bindings::drm_connector_helper_funcs {
mode_valid: None,
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 650c0b530de5..b1c68838205e 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -46,6 +46,7 @@ pub trait DriverCrtc: Send + Sync + Sized {
/// The generated C vtable for this [`DriverCrtc`] implementation.
const OPS: &'static DriverCrtcOps = &DriverCrtcOps {
funcs: bindings::drm_crtc_funcs {
+ atomic_create_state: None,
atomic_destroy_state: Some(atomic_destroy_state_callback::<Self::State>),
atomic_duplicate_state: Some(atomic_duplicate_state_callback::<Self::State>),
atomic_get_property: None,
@@ -107,8 +108,8 @@ pub trait DriverCrtc: Send + Sync + Sized {
},
mode_set_nofb: None,
mode_set_base: None,
- mode_set_base_atomic: None,
get_scanout_position: None,
+ handle_vblank_timeout: None,
},
};
@@ -995,14 +996,14 @@ impl<'a, T: DriverCrtc> CrtcAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_check_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) -> i32 {
// SAFETY:
// - We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
// - We're guaranteed by DRM that `crtc` is pointing to a valid initialized state.
let crtc = unsafe { Crtc::from_raw(crtc) };
- // SAFETY: DRM guarantees `state` points to a valid `drm_atomic_state`
+ // SAFETY: DRM guarantees `state` points to a valid `drm_atomic_commit`
// We use a ManuallyDrop here to avoid AtomicStateComposer dropping an owned reference we never
// acquired.
let state =
@@ -1023,14 +1024,15 @@ impl<'a, T: DriverCrtc> CrtcAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_begin_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// * We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
// * We're guaranteed by DRM that `crtc` is pointing to a valid initialized state.
let crtc = unsafe { Crtc::from_raw(crtc) };
- // SAFETY: We're guaranteed by DRM that `state` points to a valid instance of `drm_atomic_state`
+ // SAFETY: DRM guarantees that `state` points to a valid
+ // `drm_atomic_commit`.
let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
// SAFETY:
@@ -1045,14 +1047,15 @@ impl<'a, T: DriverCrtc> CrtcAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_flush_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// - We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
// - We're guaranteed by DRM that `crtc` is pointing to a valid initialized state.
let crtc = unsafe { Crtc::from_raw(crtc) };
- // SAFETY: We're guaranteed by DRM that `state` points to a valid instance of `drm_atomic_state`
+ // SAFETY: DRM guarantees that `state` points to a valid
+ // `drm_atomic_commit`.
let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
// SAFETY:
@@ -1067,7 +1070,7 @@ impl<'a, T: DriverCrtc> CrtcAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_enable_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// - We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
@@ -1089,7 +1092,7 @@ impl<'a, T: DriverCrtc> CrtcAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_disable_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// - We're guaranteed `crtc` points to a valid instance of `drm_crtc`
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 2791d341f1ac..0c549dece483 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -46,6 +46,7 @@ pub trait DriverPlane: Send + Sync + Sized {
/// The generated C vtable for this [`DriverPlane`] implementation.
const OPS: &'static DriverPlaneOps = &DriverPlaneOps {
funcs: bindings::drm_plane_funcs {
+ atomic_create_state: None,
update_plane: Some(bindings::drm_atomic_helper_update_plane),
disable_plane: Some(bindings::drm_atomic_helper_disable_plane),
destroy: Some(plane_destroy_callback::<Self>),
@@ -1048,14 +1049,14 @@ impl<'a, T: DriverPlane> PlaneAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_update_callback<T: DriverPlane>(
plane: *mut bindings::drm_plane,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) {
// SAFETY:
// - We're guaranteed `plane` is of type `Plane<T>` via type invariants.
// - We're guaranteed by DRM that `plane` is pointing to a valid initialized state.
let plane = unsafe { Plane::from_raw(plane) };
- // SAFETY: DRM guarantees `state` points to a valid `drm_atomic_state`
+ // SAFETY: DRM guarantees `state` points to a valid `drm_atomic_commit`
let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
// SAFETY:
@@ -1070,14 +1071,15 @@ impl<'a, T: DriverPlane> PlaneAtomicCommit<'a, T> {
unsafe extern "C" fn atomic_check_callback<T: DriverPlane>(
plane: *mut bindings::drm_plane,
- state: *mut bindings::drm_atomic_state,
+ state: *mut bindings::drm_atomic_commit,
) -> i32 {
// SAFETY:
// - We're guaranteed `plane` is of type `Plane<T>` via type invariants.
// - We're guaranteed by DRM that `plane` is pointing to a valid initialized state.
let plane = unsafe { Plane::from_raw(plane) };
- // SAFETY: We're guaranteed by DRM that `state` points to a valid instance of `drm_atomic_state`
+ // SAFETY: DRM guarantees that `state` points to a valid
+ // `drm_atomic_commit`.
// We use ManuallyDrop here since AtomicStateComposer would otherwise drop a owned reference to
// the atomic state upon finishing this callback.
let state = ManuallyDrop::new(unsafe {
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 2/23] rust: drm: kms: tie mode-object references to their owners
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
2026-08-26 16:31 ` [PATCH v3 1/23] rust: drm: kms: adapt Lyude's KMS series to current DRM APIs Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 3/23] rust: drm: kms: constrain connector encoder attachment Mike Lothian
` (20 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
The plane and encoder constructors accepted a caller-selected output
lifetime longer than the unregistered KMS device borrow.
RawPlaneState::crtc() had the same issue relative to the state borrow.
This allowed safe callers to manufacture dangling references.
Return references with the input/owner lifetime instead. Remove the
unused second lifetime from the CRTC constructor at the same time.
Fixes: 4b14e6e6259b ("rust: drm/kms: Add drm_plane bindings")
Fixes: c07f528ca38e ("rust: drm/kms: Add drm_encoder bindings")
Fixes: 8ba1abe0de4b ("rust: drm/kms: Add RawPlaneState::crtc()")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/crtc.rs | 2 +-
rust/kernel/drm/kms/encoder.rs | 24 +++++++++++++++++--
rust/kernel/drm/kms/plane.rs | 42 +++++++++++++++++++++++++++++++---
3 files changed, 62 insertions(+), 6 deletions(-)
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index b1c68838205e..683d9ee4ec25 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -302,7 +302,7 @@ impl<T: DriverCrtc> UnregisteredCrtc<T> {
/// construct new [`UnregisteredCrtc`] objects.
///
/// [`KmsDriver::create_objects`]: kernel::drm::kms::KmsDriver::create_objects
- pub fn new<'a, 'b: 'a, PrimaryData, CursorData>(
+ pub fn new<'a, PrimaryData, CursorData>(
dev: &'a UnregisteredKmsDevice<'a, T::Driver>,
primary: &'a UnregisteredPlane<PrimaryData>,
cursor: Option<&'a UnregisteredPlane<CursorData>>,
diff --git a/rust/kernel/drm/kms/encoder.rs b/rust/kernel/drm/kms/encoder.rs
index aa6f9fbaa5f1..f90d139cdb04 100644
--- a/rust/kernel/drm/kms/encoder.rs
+++ b/rust/kernel/drm/kms/encoder.rs
@@ -273,15 +273,35 @@ impl<T: DriverEncoder> UnregisteredEncoder<T> {
/// A driver may use this from their [`KmsDriver::create_objects`] callback in order to
/// construct new [`UnregisteredEncoder`] objects.
///
+ /// The returned encoder cannot outlive the device borrow:
+ ///
+ /// ```ignore,compile_fail
+ /// use kernel::{drm::kms::{encoder::{DriverEncoder, Type, UnregisteredEncoder},
+ /// UnregisteredKmsDevice},
+ /// error::Result,
+ /// str::CStr};
+ ///
+ /// fn reject_leaking_signature<T: DriverEncoder>() {
+ /// let _: for<'a> fn(
+ /// &'a UnregisteredKmsDevice<'a, T::Driver>,
+ /// Type,
+ /// u32,
+ /// u32,
+ /// Option<&CStr>,
+ /// T::Args,
+ /// ) -> Result<&'static UnregisteredEncoder<T>> = UnregisteredEncoder::<T>::new;
+ /// }
+ /// ```
+ ///
/// [`KmsDriver::create_objects`]: kernel::drm::kms::KmsDriver::create_objects
- pub fn new<'a, 'b: 'a>(
+ pub fn new<'a>(
dev: &'a UnregisteredKmsDevice<'a, T::Driver>,
type_: Type,
possible_crtcs: u32,
possible_clones: u32,
name: Option<&CStr>,
args: T::Args,
- ) -> Result<&'b Self> {
+ ) -> Result<&'a Self> {
let this: Pin<KBox<Encoder<T>>> = KBox::try_pin_init(
try_pin_init!(Encoder {
encoder: Opaque::new(bindings::drm_encoder {
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 0c549dece483..f52f9c872de3 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -255,8 +255,29 @@ impl<T: DriverPlane> UnregisteredPlane<T> {
/// A driver may use this from their [`KmsDriver::create_objects`] callback in order to
/// construct new [`UnregisteredPlane`] objects.
///
+ /// The returned plane cannot outlive the device borrow:
+ ///
+ /// ```ignore,compile_fail
+ /// use kernel::{drm::kms::{plane::{DriverPlane, Type, UnregisteredPlane},
+ /// UnregisteredKmsDevice},
+ /// error::Result,
+ /// str::CStr};
+ ///
+ /// fn reject_leaking_signature<T: DriverPlane>() {
+ /// let _: for<'a> fn(
+ /// &'a UnregisteredKmsDevice<'a, T::Driver>,
+ /// u32,
+ /// &[u32],
+ /// Option<&[u64]>,
+ /// Type,
+ /// Option<&CStr>,
+ /// T::Args,
+ /// ) -> Result<&'static UnregisteredPlane<T>> = UnregisteredPlane::<T>::new;
+ /// }
+ /// ```
+ ///
/// [`KmsDriver::create_objects`]: kernel::drm::kms::KmsDriver::create_objects
- pub fn new<'a, 'b: 'a>(
+ pub fn new<'a>(
dev: &'a UnregisteredKmsDevice<'a, T::Driver>,
possible_crtcs: u32,
formats: &[u32],
@@ -264,7 +285,7 @@ pub fn new<'a, 'b: 'a>(
type_: Type,
name: Option<&CStr>,
args: T::Args,
- ) -> Result<&'b Self> {
+ ) -> Result<&'a Self> {
let this: Pin<KBox<Plane<T>>> = KBox::try_pin_init(
try_pin_init!(Plane {
plane: Opaque::new(bindings::drm_plane {
@@ -597,7 +618,22 @@ fn plane(&self) -> &Self::Plane {
}
/// Return the current [`OpaqueCrtc`] assigned to this plane, if there is one.
- fn crtc<'a, 'b: 'a, D>(&'a self) -> Option<&'b OpaqueCrtc<D>>
+ ///
+ /// The returned CRTC reference cannot outlive the plane-state borrow:
+ ///
+ /// ```ignore,compile_fail
+ /// use kernel::drm::kms::{crtc::OpaqueCrtc, plane::RawPlaneState, KmsDriver, ModeObject};
+ ///
+ /// fn reject_leaking_signature<S, D>()
+ /// where
+ /// S: RawPlaneState,
+ /// S::Plane: ModeObject<Driver = D>,
+ /// D: KmsDriver,
+ /// {
+ /// let _: for<'a> fn(&'a S) -> Option<&'static OpaqueCrtc<D>> = S::crtc::<D>;
+ /// }
+ /// ```
+ fn crtc<D>(&self) -> Option<&OpaqueCrtc<D>>
where
Self::Plane: ModeObject<Driver = D>,
D: KmsDriver,
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 3/23] rust: drm: kms: constrain connector encoder attachment
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
2026-08-26 16:31 ` [PATCH v3 1/23] rust: drm: kms: adapt Lyude's KMS series to current DRM APIs Mike Lothian
2026-08-26 16:31 ` [PATCH v3 2/23] rust: drm: kms: tie mode-object references to their owners Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 4/23] rust: drm: reject cross-device GEM handle creation Mike Lothian
` (19 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
drm_connector_attach_encoder() requires both objects to belong to the same
DRM device. The safe wrapper previously accepted any AsRawEncoder,
including an encoder from another driver or device.
Accept only an UnregisteredEncoder from the same KMS driver and reject a
different device instance before entering C.
Fixes: 322a9b8d699b ("rust: drm/kms: Add UnregisteredConnector::attach_encoder()")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/connector.rs | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index 78b08b94587b..b36d138ae950 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -404,11 +404,22 @@ pub fn new<'a>(
/// Attach an encoder to this [`Connector`].
#[must_use]
- pub fn attach_encoder(&self, encoder: &impl AsRawEncoder) -> Result {
+ pub fn attach_encoder<E>(&self, encoder: &UnregisteredEncoder<E>) -> Result
+ where
+ E: DriverEncoder<Driver = T::Driver>,
+ {
+ // SAFETY: Both unregistered objects have been initialized, so their parent device
+ // pointers are valid and invariant for their lifetimes.
+ let same_device = unsafe { (*self.as_raw()).dev == (*encoder.as_raw()).dev };
+ if !same_device {
+ return Err(EINVAL);
+ }
+
// SAFETY:
- // - Both as_raw() calls are guaranteed to return a valid pointer
- // - We're guaranteed this connector is not registered via our type invariants, thus this
- // function is safe to call
+ // - Both `as_raw()` calls return valid pointers.
+ // - The generic bound and check above prove that both objects belong to the same driver
+ // and device.
+ // - `self` is unregistered, as required by the C API.
to_result(unsafe {
bindings::drm_connector_attach_encoder(self.as_raw(), encoder.as_raw())
})
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 4/23] rust: drm: reject cross-device GEM handle creation
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (2 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 3/23] rust: drm: kms: constrain connector encoder attachment Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 5/23] rust: drm: kms: add common state and connector helpers Mike Lothian
` (18 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Janne Grunau, Asahi Lina,
rust-for-linux, linux-kernel
The Rust type bounds prove that a GEM object and file use the same
driver implementation, but one driver can own multiple DRM device
instances. drm_gem_handle_create() also requires the object and file
to belong to the same instance.
Expose the owning device pointer within the DRM crate and return
EINVAL for a mismatched instance.
Fixes: c284d3e42338 ("rust: drm: gem: Add GEM object abstraction")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/file.rs | 7 +++++++
rust/kernel/drm/gem/mod.rs | 7 +++++++
2 files changed, 14 insertions(+)
diff --git a/rust/kernel/drm/file.rs b/rust/kernel/drm/file.rs
index 10160601ce5a..0abb7813f011 100644
--- a/rust/kernel/drm/file.rs
+++ b/rust/kernel/drm/file.rs
@@ -45,6 +45,13 @@ pub(super) fn as_raw(&self) -> *mut bindings::drm_file {
self.0.get()
}
+ /// Return the DRM device that owns this open file.
+ pub(crate) fn device_raw(&self) -> *mut bindings::drm_device {
+ // SAFETY: An open `drm_file` has a valid `minor`, whose `dev` pointer remains valid for
+ // the lifetime of the file.
+ unsafe { (*(*self.as_raw()).minor).dev }
+ }
+
fn driver_priv(&self) -> *mut T {
// SAFETY: By the type invariants of `Self`, `self.as_raw()` is always valid.
unsafe { (*self.as_raw()).driver_priv }.cast()
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 60491e5521e4..334e946833fb 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -186,6 +186,13 @@ fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
D: drm::Driver<Object = Self, File = F>,
F: drm::file::DriverFile<Driver = D>,
{
+ // The associated-type bounds prove a common driver type; separately reject another
+ // instance of that driver before passing the pair to the C API.
+ // SAFETY: `self.as_raw()` is a valid GEM object by the trait invariant.
+ if unsafe { (*self.as_raw()).dev } != file.device_raw() {
+ return Err(EINVAL);
+ }
+
let mut handle: u32 = 0;
// SAFETY: The arguments are all valid per the type invariants.
to_result(unsafe {
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 5/23] rust: drm: kms: add common state and connector helpers
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (3 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 4/23] rust: drm: reject cross-device GEM handle creation Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 6/23] rust: drm: expose HDCP 2.2 message identifiers Mike Lothian
` (17 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Add safe KMS helpers for hotplug events, mode timings, CRTC modes,
plane destination sizes, and EDID mode enumeration.
Propagate drm_edid_connector_update() failures and release the
temporary EDID on every path.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms.rs | 18 +++++---
rust/kernel/drm/kms/connector.rs | 35 ++++++++++++++-
rust/kernel/drm/kms/crtc.rs | 12 ++++-
rust/kernel/drm/kms/encoder.rs | 9 +---
rust/kernel/drm/kms/modes.rs | 77 +++++++++++++++++++++++++++++++-
rust/kernel/drm/kms/plane.rs | 14 +++++-
rust/kernel/drm/kms/vblank.rs | 2 +-
7 files changed, 148 insertions(+), 19 deletions(-)
diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
index 8baf9c2906f5..c10b2488af9b 100644
--- a/rust/kernel/drm/kms.rs
+++ b/rust/kernel/drm/kms.rs
@@ -77,7 +77,7 @@ unsafe fn setup_kms(_drm: &Device<Self::Driver>) -> Result<ModeConfigInfo> {
/// generate said functions for any kind of type which the original mode object driver trait can be
/// derived from. All conversions check the mode object's vtable. For example:
///
-/// ```compile_fail
+/// ```ignore
/// impl<'a, T: DriverConnectorState> ConnectorState<T> {
/// impl_from_opaque_mode_obj! {
/// // | An optional lifetime and param-variables to declare for each function
@@ -245,10 +245,7 @@ pub trait KmsDriver: Driver {
type Encoder: encoder::DriverEncoder<Driver = Self>;
/// Return a [`ModeConfigInfo`] structure for this [`device::Device`].
- fn mode_config_info(
- dev: &device::Device,
- drm_data: &Self::Data,
- ) -> Result<ModeConfigInfo>;
+ fn mode_config_info(dev: &device::Device, drm_data: &Self::Data) -> Result<ModeConfigInfo>;
/// Create mode objects like [`crtc::Crtc`], [`plane::Plane`], etc. for this device
fn create_objects(drm: &UnregisteredKmsDevice<'_, Self>) -> Result
@@ -360,6 +357,17 @@ impl<T: Driver> private::KmsImpl for PhantomData<T> {
impl<T: Driver> KmsImpl for PhantomData<T> {}
+impl<T: KmsDriver, C: crate::drm::device::DeviceContext> Device<T, C> {
+ /// Send a hotplug uevent to userspace, prompting it to re-probe connector state.
+ ///
+ /// This is useful for drivers which detect connector changes out of band, for example when a
+ /// dock supplies an EDID after bring-up.
+ pub fn hotplug_event(&self) {
+ // SAFETY: `self.as_raw()` is a live KMS-capable DRM device.
+ unsafe { bindings::drm_kms_helper_hotplug_event(self.as_raw()) };
+ }
+}
+
/// Various device-wide information for a [`Device`] that is provided during initialization.
#[derive(Copy, Clone)]
pub struct ModeConfigInfo {
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index b36d138ae950..793a7bb5bfef 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -5,7 +5,7 @@
//! C header: [`include/drm/drm_connector.h`](srctree/include/drm/drm_connector.h)
use super::{
- atomic::*, encoder::*, KmsDriver, ModeConfigGuard, ModeObject, ModeObjectVtable, Sealed
+ atomic::*, encoder::*, KmsDriver, ModeConfigGuard, ModeObject, ModeObjectVtable, Sealed,
};
use crate::{
alloc::KBox,
@@ -587,6 +587,39 @@ pub fn set_preferred_mode(&self, (h_pref, w_pref): (u32, u32)) {
// SAFETY: We hold the locks required to call this via our type invariants.
unsafe { bindings::drm_set_preferred_mode(self.as_raw(), h_pref, w_pref) }
}
+
+ /// Parse an EDID, update the connector information, and add its advertised modes.
+ ///
+ /// Returns the number of modes added.
+ pub fn add_edid_modes(&self, edid: &[u8]) -> Result<i32> {
+ const EDID_BASE_BLOCK_LEN: usize = 128;
+
+ if edid.len() < EDID_BASE_BLOCK_LEN {
+ return Err(EINVAL);
+ }
+
+ // SAFETY: `edid` points to `edid.len()` initialized bytes, which the helper copies.
+ let drm_edid = unsafe { bindings::drm_edid_alloc(edid.as_ptr().cast(), edid.len()) };
+ if drm_edid.is_null() {
+ return Err(ENOMEM);
+ }
+
+ // SAFETY: The connector is live and the guard holds the mode-config lock. `drm_edid`
+ // points to an allocation returned by `drm_edid_alloc` above.
+ let ret = unsafe { bindings::drm_edid_connector_update(self.as_raw(), drm_edid) };
+ if let Err(err) = to_result(ret) {
+ // SAFETY: `drm_edid` was allocated above and has not been freed.
+ unsafe { bindings::drm_edid_free(drm_edid) };
+ return Err(err);
+ }
+
+ // SAFETY: The connector information was successfully updated from this EDID above.
+ let count = unsafe { bindings::drm_edid_connector_add_modes(self.as_raw()) };
+ // SAFETY: `drm_edid` was allocated above and is no longer needed.
+ unsafe { bindings::drm_edid_free(drm_edid) };
+
+ Ok(count)
+ }
}
/// A trait implemented by any type which can produce a reference to a
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 683d9ee4ec25..a3217f8c55e8 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -5,8 +5,8 @@
//! C header: [`include/drm/drm_crtc.h`](srctree/include/drm/drm_crtc.h)
use super::{
- atomic::*, plane::*, vblank::*, KmsDriver, ModeObject, ModeObjectVtable, StaticModeObject,
- UnregisteredKmsDevice, Sealed,
+ atomic::*, modes::DisplayMode, plane::*, vblank::*, KmsDriver, ModeObject, ModeObjectVtable,
+ Sealed, StaticModeObject, UnregisteredKmsDevice,
};
use crate::{
alloc::KBox,
@@ -644,6 +644,7 @@ pub trait AsRawCrtcState: private::AsRawCrtcState {
pub(crate) mod private {
use super::*;
+ /// The raw-pointer half of [`AsRawCrtcState`](super::AsRawCrtcState).
#[allow(unreachable_pub)]
pub trait AsRawCrtcState {
/// Return a raw pointer to the DRM CRTC state
@@ -678,6 +679,13 @@ fn active(&self) -> bool {
// this access is serialized
unsafe { (*self.as_raw()).active }
}
+
+ /// Return the display mode programmed into this CRTC state.
+ fn mode(&self) -> &DisplayMode {
+ // SAFETY: `mode` is embedded in the CRTC state and therefore has the same lifetime. The
+ // atomic-state API serializes access while the mode can be changed.
+ unsafe { DisplayMode::as_ref(core::ptr::addr_of!((*self.as_raw()).mode)) }
+ }
}
impl<T: AsRawCrtcState> RawCrtcState for T {}
diff --git a/rust/kernel/drm/kms/encoder.rs b/rust/kernel/drm/kms/encoder.rs
index f90d139cdb04..8758a9459bcc 100644
--- a/rust/kernel/drm/kms/encoder.rs
+++ b/rust/kernel/drm/kms/encoder.rs
@@ -5,7 +5,7 @@
//! C header: [`include/drm/drm_encoder.h`](srctree/include/drm/drm_encoder.h)
use super::{
- KmsDriver, ModeObject, ModeObjectVtable, StaticModeObject, UnregisteredKmsDevice, Sealed
+ KmsDriver, ModeObject, ModeObjectVtable, Sealed, StaticModeObject, UnregisteredKmsDevice,
};
use crate::{
alloc::KBox,
@@ -15,12 +15,7 @@
types::{NotThreadSafe, Opaque},
};
use bindings;
-use core::{
- marker::*,
- mem,
- ops::Deref,
- ptr::null,
-};
+use core::{marker::*, mem, ops::Deref, ptr::null};
use macros::paste;
/// A macro for generating our type ID enumerator.
diff --git a/rust/kernel/drm/kms/modes.rs b/rust/kernel/drm/kms/modes.rs
index 0f29a9c00062..cc3c486eecf1 100644
--- a/rust/kernel/drm/kms/modes.rs
+++ b/rust/kernel/drm/kms/modes.rs
@@ -1,7 +1,12 @@
// SPDX-License-Identifier: GPL-2.0
+//!
+//! DRM display modes.
+//!
+//! C header: [`include/drm/drm_modes.h`](srctree/include/drm/drm_modes.h)
+
use bindings;
-use crate::{prelude::*, types::Opaque};
+use crate::types::Opaque;
/// DRM kernel-internal display mode structure.
///
@@ -73,4 +78,74 @@ pub fn crtc_vtotal(&self) -> u16 {
// SAFETY: Reading these fields is safe via our type invariants
unsafe { (*self.as_raw()).crtc_vtotal }
}
+
+ /// Return the horizontal active pixels.
+ #[inline]
+ pub fn hdisplay(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).hdisplay }
+ }
+
+ /// Return the start of the horizontal sync pulse.
+ #[inline]
+ pub fn hsync_start(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).hsync_start }
+ }
+
+ /// Return the end of the horizontal sync pulse.
+ #[inline]
+ pub fn hsync_end(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).hsync_end }
+ }
+
+ /// Return the total horizontal pixels including blanking.
+ #[inline]
+ pub fn htotal(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).htotal }
+ }
+
+ /// Return the vertical active scanlines.
+ #[inline]
+ pub fn vdisplay(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).vdisplay }
+ }
+
+ /// Return the start of the vertical sync pulse.
+ #[inline]
+ pub fn vsync_start(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).vsync_start }
+ }
+
+ /// Return the end of the vertical sync pulse.
+ #[inline]
+ pub fn vsync_end(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).vsync_end }
+ }
+
+ /// Return the total vertical scanlines including blanking.
+ #[inline]
+ pub fn vtotal(&self) -> u16 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).vtotal }
+ }
+
+ /// Return the pixel clock in kHz.
+ #[inline]
+ pub fn clock(&self) -> i32 {
+ // SAFETY: Reading this field is safe via the type invariants.
+ unsafe { (*self.as_raw()).clock }
+ }
+
+ /// Return the refresh rate in Hz as computed by DRM.
+ #[inline]
+ pub fn vrefresh(&self) -> i32 {
+ // SAFETY: `drm_mode_vrefresh` only reads this valid display mode.
+ unsafe { bindings::drm_mode_vrefresh(self.as_raw()) }
+ }
}
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index f52f9c872de3..3a95c45b6728 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -5,8 +5,8 @@
//! C header: [`include/drm/drm_plane.h`](srctree/include/drm/drm_plane.h)
use super::{
- atomic::*, crtc::*, framebuffer::*, KmsDriver, ModeObject, ModeObjectVtable, StaticModeObject,
- UnregisteredKmsDevice, Sealed
+ atomic::*, crtc::*, framebuffer::*, KmsDriver, ModeObject, ModeObjectVtable, Sealed,
+ StaticModeObject, UnregisteredKmsDevice,
};
use crate::{
alloc::KBox,
@@ -617,6 +617,16 @@ fn plane(&self) -> &Self::Plane {
unsafe { Self::Plane::from_raw(self.as_raw().plane) }
}
+ /// Return the width of this plane's destination rectangle in CRTC pixels.
+ fn crtc_w(&self) -> u32 {
+ self.as_raw().crtc_w
+ }
+
+ /// Return the height of this plane's destination rectangle in CRTC pixels.
+ fn crtc_h(&self) -> u32 {
+ self.as_raw().crtc_h
+ }
+
/// Return the current [`OpaqueCrtc`] assigned to this plane, if there is one.
///
/// The returned CRTC reference cannot outlive the plane-state borrow:
diff --git a/rust/kernel/drm/kms/vblank.rs b/rust/kernel/drm/kms/vblank.rs
index dc34e02e8ccb..a725a46110d8 100644
--- a/rust/kernel/drm/kms/vblank.rs
+++ b/rust/kernel/drm/kms/vblank.rs
@@ -4,7 +4,7 @@
//!
//! C header: [`include/drm/drm_vblank.h`](srcfree/include/drm/drm_vblank.h)
-use super::{crtc::*, ModeObject, modes::*, Sealed};
+use super::{crtc::*, modes::*, ModeObject};
use bindings;
use core::{
marker::*,
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 6/23] rust: drm: expose HDCP 2.2 message identifiers
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (4 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 5/23] rust: drm: kms: add common state and connector helpers Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 7/23] rust: drm: kms: add typed color and rotation properties Mike Lothian
` (16 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, David Airlie, Simona Vetter,
Lyude Paul, Greg Kroah-Hartman, Asahi Lina, Lorenzo Stoakes,
Joel Fernandes, linux-kernel, rust-for-linux
Add a DRM display module with typed identifiers for the standard
HDCP 2.2 protocol messages. Transport drivers can use the canonical
drm_hdcp.h values without reaching into generated bindings.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/bindings/bindings_helper.h | 1 +
rust/kernel/drm/display.rs | 5 +++
rust/kernel/drm/display/hdcp.rs | 77 +++++++++++++++++++++++++++++++++
rust/kernel/drm/mod.rs | 1 +
4 files changed, 84 insertions(+)
create mode 100644 rust/kernel/drm/display.rs
create mode 100644 rust/kernel/drm/display/hdcp.rs
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 8db7fe00fa1b..ae3017539767 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -34,6 +34,7 @@
#include <linux/acpi.h>
#include <linux/gpu_buddy.h>
+#include <drm/display/drm_hdcp.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/clients/drm_client_setup.h>
diff --git a/rust/kernel/drm/display.rs b/rust/kernel/drm/display.rs
new file mode 100644
index 000000000000..007ed284c551
--- /dev/null
+++ b/rust/kernel/drm/display.rs
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! DRM display-helper abstractions.
+
+pub mod hdcp;
diff --git a/rust/kernel/drm/display/hdcp.rs b/rust/kernel/drm/display/hdcp.rs
new file mode 100644
index 000000000000..966fb67c6f31
--- /dev/null
+++ b/rust/kernel/drm/display/hdcp.rs
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! High-bandwidth Digital Content Protection definitions.
+//!
+//! C header: [`include/drm/display/drm_hdcp.h`](srctree/include/drm/display/drm_hdcp.h)
+
+use crate::bindings;
+
+/// Transmitter nonce length.
+pub const RTX_LEN: usize = bindings::HDCP_2_2_RTX_LEN as usize;
+/// Receiver nonce length.
+pub const RRX_LEN: usize = bindings::HDCP_2_2_RRX_LEN as usize;
+/// Receiver RSA modulus length.
+pub const RSA_MODULUS_LEN: usize = bindings::HDCP_2_2_K_PUB_RX_MOD_N_LEN as usize;
+/// Receiver RSA public exponent length.
+pub const RSA_EXPONENT_LEN: usize = bindings::HDCP_2_2_K_PUB_RX_EXP_E_LEN as usize;
+/// Encrypted master-key length.
+pub const ENCRYPTED_MASTER_KEY_LEN: usize = bindings::HDCP_2_2_E_KPUB_KM_LEN as usize;
+/// H-prime verifier length.
+pub const H_PRIME_LEN: usize = bindings::HDCP_2_2_H_PRIME_LEN as usize;
+/// Locality-check nonce length.
+pub const RN_LEN: usize = bindings::HDCP_2_2_RN_LEN as usize;
+/// L-prime verifier length.
+pub const L_PRIME_LEN: usize = bindings::HDCP_2_2_L_PRIME_LEN as usize;
+/// Encrypted session-key length.
+pub const ENCRYPTED_SESSION_KEY_LEN: usize = bindings::HDCP_2_2_E_DKEY_KS_LEN as usize;
+/// Session-key nonce length.
+pub const RIV_LEN: usize = bindings::HDCP_2_2_RIV_LEN as usize;
+/// One half of the repeater V-prime verifier.
+pub const V_PRIME_HALF_LEN: usize = bindings::HDCP_2_2_V_PRIME_HALF_LEN as usize;
+
+/// An HDCP 2.2 protocol message identifier.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct MessageId(u8);
+
+impl MessageId {
+ /// No message.
+ pub const NULL: Self = Self(bindings::HDCP_2_2_NULL_MSG as u8);
+ /// Authentication and Key Exchange initialization.
+ pub const AKE_INIT: Self = Self(bindings::HDCP_2_2_AKE_INIT as u8);
+ /// Receiver certificate.
+ pub const AKE_SEND_CERT: Self = Self(bindings::HDCP_2_2_AKE_SEND_CERT as u8);
+ /// Encrypted master key for a receiver without stored pairing information.
+ pub const AKE_NO_STORED_KM: Self = Self(bindings::HDCP_2_2_AKE_NO_STORED_KM as u8);
+ /// Encrypted master key and pairing nonce for a paired receiver.
+ pub const AKE_STORED_KM: Self = Self(bindings::HDCP_2_2_AKE_STORED_KM as u8);
+ /// Receiver's H-prime authentication value.
+ pub const AKE_SEND_H_PRIME: Self = Self(bindings::HDCP_2_2_AKE_SEND_HPRIME as u8);
+ /// Receiver pairing information.
+ pub const AKE_SEND_PAIRING_INFO: Self = Self(bindings::HDCP_2_2_AKE_SEND_PAIRING_INFO as u8);
+ /// Locality-check initialization.
+ pub const LC_INIT: Self = Self(bindings::HDCP_2_2_LC_INIT as u8);
+ /// Receiver's L-prime locality-check value.
+ pub const LC_SEND_L_PRIME: Self = Self(bindings::HDCP_2_2_LC_SEND_LPRIME as u8);
+ /// Session-key exchange.
+ pub const SKE_SEND_EKS: Self = Self(bindings::HDCP_2_2_SKE_SEND_EKS as u8);
+ /// Repeater receiver-ID list.
+ pub const REPEATERAUTH_SEND_RECEIVERID_LIST: Self =
+ Self(bindings::HDCP_2_2_REP_SEND_RECVID_LIST as u8);
+ /// Repeater receiver-ID-list acknowledgment.
+ pub const REPEATERAUTH_SEND_ACK: Self = Self(bindings::HDCP_2_2_REP_SEND_ACK as u8);
+ /// Repeater stream-management request.
+ pub const REPEATERAUTH_STREAM_MANAGE: Self = Self(bindings::HDCP_2_2_REP_STREAM_MANAGE as u8);
+ /// Repeater stream-ready response.
+ pub const REPEATERAUTH_STREAM_READY: Self = Self(bindings::HDCP_2_2_REP_STREAM_READY as u8);
+
+ /// Return the wire value.
+ pub const fn as_u8(self) -> u8 {
+ self.0
+ }
+}
+
+impl From<MessageId> for u8 {
+ fn from(value: MessageId) -> Self {
+ value.as_u8()
+ }
+}
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index 786cd9c1ec07..4576d66a6bb6 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -3,6 +3,7 @@
//! DRM subsystem abstractions.
pub mod device;
+pub mod display;
pub mod driver;
pub mod file;
pub mod fourcc;
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 7/23] rust: drm: kms: add typed color and rotation properties
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (5 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 6/23] rust: drm: expose HDCP 2.2 message identifiers Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 8/23] rust: drm: kms: add connector detect() and mode_valid() hooks Mike Lothian
` (15 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, David Airlie, Simona Vetter,
Lyude Paul, Greg Kroah-Hartman, Asahi Lina, Burak Emir,
Lorenzo Stoakes, Joel Fernandes, rust-for-linux, linux-kernel
Add typed KMS property support for CRTC gamma lookup tables and
plane rotation.
ColorLut exposes validated drm_color_lut entries without generated
bindings. Rotation represents only combinations accepted by the DRM
rotation property, while the plane state accessors expose placement
and cursor-hotspot coordinates needed by software and transport
scanout drivers.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/bindings/bindings_helper.h | 1 +
rust/kernel/drm/kms/crtc.rs | 53 ++++++++++++++++++
rust/kernel/drm/kms/plane.rs | 95 +++++++++++++++++++++++++++++++++
3 files changed, 149 insertions(+)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ae3017539767..38ad80fae0ed 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -37,6 +37,7 @@
#include <drm/display/drm_hdcp.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
+#include <drm/drm_blend.h>
#include <drm/clients/drm_client_setup.h>
#include <drm/drm_connector.h>
#include <drm/drm_crtc.h>
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index a3217f8c55e8..a7024d8921ca 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -25,6 +25,27 @@
};
use macros::vtable;
+/// One entry in a DRM gamma or degamma lookup table.
+#[repr(transparent)]
+pub struct ColorLut(bindings::drm_color_lut);
+
+impl ColorLut {
+ /// Red channel value.
+ pub fn red(&self) -> u16 {
+ self.0.red
+ }
+
+ /// Green channel value.
+ pub fn green(&self) -> u16 {
+ self.0.green
+ }
+
+ /// Blue channel value.
+ pub fn blue(&self) -> u16 {
+ self.0.blue
+ }
+}
+
/// The main trait for implementing the [`struct drm_crtc`] API for [`Crtc`].
///
/// Any KMS driver should have at least one implementation of this type, which allows them to create
@@ -357,6 +378,17 @@ pub fn new<'a, PrimaryData, CursorData>(
// SAFETY: We just allocated the crtc above, so this pointer must be valid
Ok(unsafe { &*this })
}
+
+ /// Enable colour management on this CRTC, creating a `GAMMA_LUT` property of `gamma_size`
+ /// entries that userspace can program (no degamma LUT, no CTM). The set LUT is then readable
+ /// from the CRTC state via [`RawCrtcState::gamma_lut`].
+ ///
+ /// Call this during [`KmsDriver::probe`](crate::drm::kms::KmsDriver::probe), before the device
+ /// is registered.
+ pub fn enable_gamma(&self, gamma_size: u32) {
+ // SAFETY: `as_raw()` is a valid, not-yet-registered CRTC.
+ unsafe { bindings::drm_crtc_enable_color_mgmt(self.as_raw(), 0, false, gamma_size) };
+ }
}
// SAFETY: We inherit all relevant invariants of `Crtc`
@@ -686,6 +718,27 @@ fn mode(&self) -> &DisplayMode {
// atomic-state API serializes access while the mode can be changed.
unsafe { DisplayMode::as_ref(core::ptr::addr_of!((*self.as_raw()).mode)) }
}
+
+ /// Returns the CRTC's gamma LUT for this state as an array of [`ColorLut`] entries, or
+ /// [`None`] if no gamma LUT is programmed. Requires gamma to have been enabled on the CRTC
+ /// (see [`UnregisteredCrtc::enable_gamma`]).
+ ///
+ fn gamma_lut(&self) -> Option<&[ColorLut]> {
+ // SAFETY: `as_raw()` is a valid `drm_crtc_state`.
+ let blob = unsafe { (*self.as_raw()).gamma_lut };
+ if blob.is_null() {
+ return None;
+ }
+ // SAFETY: a non-null gamma_lut blob is valid for the state's lifetime.
+ let (data, length) = unsafe { ((*blob).data, (*blob).length) };
+ let n = length / core::mem::size_of::<ColorLut>();
+ if data.is_null() || n == 0 {
+ return None;
+ }
+ // SAFETY: `ColorLut` is transparent over `drm_color_lut`; the blob holds `n` contiguous
+ // entries valid for the state's lifetime.
+ Some(unsafe { core::slice::from_raw_parts(data.cast::<ColorLut>(), n) })
+ }
}
impl<T: AsRawCrtcState> RawCrtcState for T {}
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 3a95c45b6728..8e3f711b0767 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -25,6 +25,72 @@
ptr::{null, null_mut, NonNull},
};
+/// Plane rotation and reflection properties.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Rotation(u32);
+
+impl Rotation {
+ /// No rotation.
+ pub const ROTATE_0: Self = Self(bindings::DRM_MODE_ROTATE_0);
+ /// Rotate clockwise by 90 degrees.
+ pub const ROTATE_90: Self = Self(bindings::DRM_MODE_ROTATE_90);
+ /// Rotate clockwise by 180 degrees.
+ pub const ROTATE_180: Self = Self(bindings::DRM_MODE_ROTATE_180);
+ /// Rotate clockwise by 270 degrees.
+ pub const ROTATE_270: Self = Self(bindings::DRM_MODE_ROTATE_270);
+ /// Reflect across the X axis after rotation.
+ pub const REFLECT_X: Self = Self(bindings::DRM_MODE_REFLECT_X);
+ /// Reflect across the Y axis after rotation.
+ pub const REFLECT_Y: Self = Self(bindings::DRM_MODE_REFLECT_Y);
+
+ /// Return whether every bit in `other` is set.
+ pub const fn contains(self, other: Self) -> bool {
+ self.0 & other.0 == other.0
+ }
+
+ /// Return the selected rotation without reflection bits.
+ pub const fn angle(self) -> Self {
+ Self(self.0 & bindings::DRM_MODE_ROTATE_MASK)
+ }
+
+ fn bits(self) -> u32 {
+ self.0
+ }
+}
+
+impl BitOr for Rotation {
+ type Output = Self;
+
+ fn bitor(self, rhs: Self) -> Self::Output {
+ Self(self.0 | rhs.0)
+ }
+}
+
+/// Supported plane pixel-blend modes.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct BlendModes(u32);
+
+impl BlendModes {
+ /// Source pixels are premultiplied by alpha.
+ pub const PREMULTIPLIED: Self = Self(1 << bindings::DRM_MODE_BLEND_PREMULTI);
+ /// Source pixels provide straight alpha coverage.
+ pub const COVERAGE: Self = Self(1 << bindings::DRM_MODE_BLEND_COVERAGE);
+ /// Ignore per-pixel alpha.
+ pub const PIXEL_NONE: Self = Self(1 << bindings::DRM_MODE_BLEND_PIXEL_NONE);
+
+ fn bits(self) -> u32 {
+ self.0
+ }
+}
+
+impl BitOr for BlendModes {
+ type Output = Self;
+
+ fn bitor(self, rhs: Self) -> Self::Output {
+ Self(self.0 | rhs.0)
+ }
+}
+
/// The main trait for implementing the [`struct drm_plane`] API for [`Plane`].
///
/// Any KMS driver should have at least one implementation of this type, which allows them to create
@@ -350,6 +416,28 @@ pub fn new<'a>(
// SAFETY: We just allocated the plane above, so this pointer must be valid
Ok(unsafe { &*this })
}
+
+ /// Attach a rotation property to this plane, advertising `supported_rotations` (a bitmask of
+ /// `DRM_MODE_ROTATE_*` | `DRM_MODE_REFLECT_*`) with initial value `default_rotation`. The
+ /// selected value is then readable from the plane state via
+ /// [`RawPlaneState::rotation`](crate::drm::kms::plane::RawPlaneState::rotation).
+ ///
+ /// Call this during [`KmsDriver::probe`](crate::drm::kms::KmsDriver::probe), before the device
+ /// is registered.
+ pub fn create_rotation_property(
+ &self,
+ default_rotation: Rotation,
+ supported_rotations: Rotation,
+ ) -> Result {
+ // SAFETY: `as_raw()` is a valid, not-yet-registered plane.
+ to_result(unsafe {
+ bindings::drm_plane_create_rotation_property(
+ self.as_raw(),
+ default_rotation.bits(),
+ supported_rotations.bits(),
+ )
+ })
+ }
}
/// A trait implemented by any type that acts as a [`struct drm_plane`] interface.
@@ -627,6 +715,13 @@ fn crtc_h(&self) -> u32 {
self.as_raw().crtc_h
}
+ /// The plane's rotation/reflection (`DRM_MODE_ROTATE_*` | `DRM_MODE_REFLECT_*` bitmask), for a
+ /// plane with a rotation property (see
+ /// [`UnregisteredPlane::create_rotation_property`]). Defaults to `DRM_MODE_ROTATE_0`.
+ fn rotation(&self) -> Rotation {
+ Rotation(self.as_raw().rotation)
+ }
+
/// Return the current [`OpaqueCrtc`] assigned to this plane, if there is one.
///
/// The returned CRTC reference cannot outlive the plane-state borrow:
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 8/23] rust: drm: kms: add connector detect() and mode_valid() hooks
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (6 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 7/23] rust: drm: kms: add typed color and rotation properties Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 9/23] rust: drm: kms: add plane damage-clip accessors Mike Lothian
` (14 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Add optional connector detect() and mode_valid() callbacks to the
safe KMS API.
Map connector status and common mode-validation results through typed
enums. Connectors which do not implement the callbacks retain the
DRM defaults of connected and mode-valid.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/connector.rs | 141 ++++++++++++++++++++++++++++++-
1 file changed, 138 insertions(+), 3 deletions(-)
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index 793a7bb5bfef..dd126469788f 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -5,7 +5,8 @@
//! C header: [`include/drm/drm_connector.h`](srctree/include/drm/drm_connector.h)
use super::{
- atomic::*, encoder::*, KmsDriver, ModeConfigGuard, ModeObject, ModeObjectVtable, Sealed,
+ atomic::*, encoder::*, modes::DisplayMode, KmsDriver, ModeConfigGuard, ModeObject,
+ ModeObjectVtable, Sealed,
};
use crate::{
alloc::KBox,
@@ -72,6 +73,43 @@ pub enum Type {
USB as Usb
}
+/// The connection status of a [`Connector`], as returned by [`DriverConnector::detect`].
+///
+/// This is identical to [`enum drm_connector_status`].
+///
+/// [`enum drm_connector_status`]: srctree/include/drm/drm_connector.h
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(u32)]
+pub enum Status {
+ /// The connector is connected to a display and a mode list can be retrieved.
+ Connected = bindings::drm_connector_status_connector_status_connected,
+ /// The connector has no display attached.
+ Disconnected = bindings::drm_connector_status_connector_status_disconnected,
+ /// The connection state could not be determined (treated as connected for probing).
+ Unknown = bindings::drm_connector_status_connector_status_unknown,
+}
+
+/// The result of validating a display mode against a [`Connector`], as returned by
+/// [`DriverConnector::mode_valid`].
+///
+/// This mirrors a small, commonly-used subset of [`enum drm_mode_status`]; use [`ModeStatus::Bad`]
+/// for a generic rejection, or the clock-specific variants when a mode is out of the driver's
+/// pixel-clock range.
+///
+/// [`enum drm_mode_status`]: srctree/include/drm/drm_modes.h
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(i32)]
+pub enum ModeStatus {
+ /// The mode is usable.
+ Ok = bindings::drm_mode_status_MODE_OK,
+ /// The mode is rejected for an unspecified reason.
+ Bad = bindings::drm_mode_status_MODE_BAD,
+ /// The mode's pixel clock is above what the driver can drive.
+ ClockHigh = bindings::drm_mode_status_MODE_CLOCK_HIGH,
+ /// The mode's pixel clock is below what the driver can drive.
+ ClockLow = bindings::drm_mode_status_MODE_CLOCK_LOW,
+}
+
/// The main trait for implementing the [`struct drm_connector`] API for [`Connector`].
///
/// Any KMS driver should have at least one implementation of this type, which allows them to create
@@ -106,7 +144,11 @@ pub trait DriverConnector: Send + Sync + Sized {
atomic_destroy_state: Some(atomic_destroy_state_callback::<Self::State>),
destroy: Some(connector_destroy_callback::<Self>),
force: None,
- detect: None,
+ detect: if Self::HAS_DETECT {
+ Some(detect_callback::<Self>)
+ } else {
+ None
+ },
fill_modes: Some(bindings::drm_helper_probe_single_connector_modes),
debugfs_init: None,
oob_hotplug_event: None,
@@ -114,7 +156,11 @@ pub trait DriverConnector: Send + Sync + Sized {
color_format: None,
},
helper_funcs: bindings::drm_connector_helper_funcs {
- mode_valid: None,
+ mode_valid: if Self::HAS_MODE_VALID {
+ Some(mode_valid_callback::<Self>)
+ } else {
+ None
+ },
atomic_check: None,
get_modes: Some(get_modes_callback::<Self>),
detect_ctx: None,
@@ -153,6 +199,31 @@ fn get_modes<'a>(
connector: ConnectorGuard<'a, Self>,
guard: &ModeConfigGuard<'a, Self::Driver>,
) -> i32;
+
+ /// The optional [`drm_connector_funcs.detect`] hook for this connector.
+ ///
+ /// Drivers may implement this to report whether a display is currently attached. If not
+ /// implemented, the connector is always considered connected (DRM's default with no `detect`
+ /// hook). `force` is set when userspace explicitly requested a forced probe.
+ ///
+ /// [`drm_connector_funcs.detect`]: srctree/include/drm/drm_connector.h
+ fn detect(_connector: &Connector<Self>, _force: bool) -> Status {
+ build_error::build_error("This should not be reachable")
+ }
+
+ /// The optional [`drm_connector_helper_funcs.mode_valid`] hook for this connector.
+ ///
+ /// Drivers may implement this to reject modes they cannot drive (for example, a mode whose
+ /// pixel clock exceeds the hardware's budget). Returning anything other than [`ModeStatus::Ok`]
+ /// prunes the mode from the probed list. If not implemented, every mode is accepted.
+ ///
+ /// [`drm_connector_helper_funcs.mode_valid`]: srctree/include/drm/drm_modeset_helper_vtables.h
+ fn mode_valid(
+ _connector: ConnectorModeValidation<'_, Self>,
+ _mode: &DisplayMode,
+ ) -> ModeStatus {
+ build_error::build_error("This should not be reachable")
+ }
}
/// The generated C vtable for a [`DriverConnector`].
@@ -477,6 +548,32 @@ impl<T: AsRawConnector> RawConnector for T {}
T::get_modes(connector.guard(&guard), &guard)
}
+unsafe extern "C" fn detect_callback<T: DriverConnector>(
+ connector: *mut bindings::drm_connector,
+ force: bool,
+) -> bindings::drm_connector_status {
+ // SAFETY: This is safe via `DriverConnector`s type invariants.
+ let connector = unsafe { Connector::<T>::from_raw(connector) };
+
+ T::detect(connector, force) as bindings::drm_connector_status
+}
+
+unsafe extern "C" fn mode_valid_callback<T: DriverConnector>(
+ connector: *mut bindings::drm_connector,
+ mode: *const bindings::drm_display_mode,
+) -> bindings::drm_mode_status {
+ // SAFETY: This is safe via `DriverConnector`s type invariants.
+ let connector = unsafe { Connector::<T>::from_raw(connector) };
+
+ // SAFETY: DRM guarantees `mode` points to a valid `drm_display_mode` for the duration of this
+ // callback, and only passes us shared access to it.
+ let mode = unsafe { DisplayMode::as_ref(mode) };
+
+ // DRM invokes the connector helper while the mode list is stable. Keep that guarantee in a
+ // capability type so drivers can safely compare this mode with the other probed modes.
+ T::mode_valid(ConnectorModeValidation(connector), mode) as bindings::drm_mode_status
+}
+
/// A [`struct drm_connector`] without a known [`DriverConnector`] implementation.
///
/// This is mainly for situations where our bindings can't infer the [`DriverConnector`]
@@ -572,6 +669,44 @@ fn deref(&self) -> &Self::Target {
}
}
+/// A connector being validated while its mode list is stable.
+///
+/// This is only constructed by the DRM connector-helper callback. It permits read-only iteration
+/// over the connector's modes without exposing list pointers or extending a mode reference beyond
+/// the callback.
+#[derive(Copy, Clone)]
+pub struct ConnectorModeValidation<'a, T: DriverConnector>(&'a Connector<T>);
+
+impl<T: DriverConnector> Deref for ConnectorModeValidation<'_, T> {
+ type Target = Connector<T>;
+
+ fn deref(&self) -> &Self::Target {
+ self.0
+ }
+}
+
+impl<T: DriverConnector> ConnectorModeValidation<'_, T> {
+ /// Return whether any mode currently on this connector satisfies `predicate`.
+ pub fn any_mode(&self, mut predicate: impl FnMut(&DisplayMode) -> bool) -> bool {
+ let raw = self.as_raw();
+ // SAFETY: DRM only constructs this capability while `connector->modes` is stable. Each
+ // list entry is an initialized `drm_display_mode`, and the shared reference is confined to
+ // this callback invocation.
+ unsafe {
+ let head: *mut bindings::list_head = &raw mut (*raw).modes;
+ let mut node = (*head).next;
+ while node != head {
+ let mode = crate::container_of!(node, bindings::drm_display_mode, head);
+ if predicate(DisplayMode::as_ref(mode)) {
+ return true;
+ }
+ node = (*node).next;
+ }
+ }
+ false
+ }
+}
+
impl<'a, T: DriverConnector> ConnectorGuard<'a, T> {
/// Add modes for a [`ConnectorGuard`] without an EDID.
///
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 9/23] rust: drm: kms: add plane damage-clip accessors
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (7 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 8/23] rust: drm: kms: add connector detect() and mode_valid() hooks Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 10/23] rust: drm: framebuffer: add validated shmem scanout views Mike Lothian
` (13 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, David Airlie, Simona Vetter,
Lyude Paul, Asahi Lina, Matthew Maurer, Lorenzo Stoakes,
Joel Fernandes, Greg Kroah-Hartman, rust-for-linux, linux-kernel
Add safe access to the FB_DAMAGE_CLIPS rectangles intersected with
the visible source area.
damage_merged() returns the bounding rectangle produced by
drm_atomic_helper_damage_merged(). for_each_damage_clip() wraps
the DRM damage iterator for drivers that can process the individual
rectangles without repainting their bounding box.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/bindings/bindings_helper.h | 1 +
rust/kernel/drm/kms/plane.rs | 105 ++++++++++++++++++++++++++++++++
2 files changed, 106 insertions(+)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 38ad80fae0ed..c4abdd887699 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -41,6 +41,7 @@
#include <drm/clients/drm_client_setup.h>
#include <drm/drm_connector.h>
#include <drm/drm_crtc.h>
+#include <drm/drm_damage_helper.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_edid.h>
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 8e3f711b0767..3bff4091abb2 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -693,6 +693,49 @@ pub trait FromRawPlaneState: AsRawPlaneState {
unsafe fn from_raw_mut<'a>(ptr: *mut bindings::drm_plane_state) -> &'a mut Self;
}
+/// A rectangle in a plane's source (pixel) space, as produced by
+/// [`RawPlaneState::damage_merged`].
+///
+/// The box is inclusive on the top-left and exclusive on the bottom-right (`[x1, x2)` by
+/// `[y1, y2)`), matching [`struct drm_rect`].
+///
+/// [`struct drm_rect`]: srctree/include/drm/drm_rect.h
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Rect {
+ /// Left edge, inclusive.
+ pub x1: i32,
+ /// Top edge, inclusive.
+ pub y1: i32,
+ /// Right edge, exclusive.
+ pub x2: i32,
+ /// Bottom edge, exclusive.
+ pub y2: i32,
+}
+
+impl Rect {
+ #[inline]
+ fn from_raw(r: &bindings::drm_rect) -> Self {
+ Self {
+ x1: r.x1,
+ y1: r.y1,
+ x2: r.x2,
+ y2: r.y2,
+ }
+ }
+
+ /// The width of the rectangle in pixels.
+ #[inline]
+ pub fn width(&self) -> i32 {
+ self.x2 - self.x1
+ }
+
+ /// The height of the rectangle in pixels.
+ #[inline]
+ pub fn height(&self) -> i32 {
+ self.y2 - self.y1
+ }
+}
+
/// Common methods available on any type which implements [`AsRawPlane`].
///
/// This is implemented internally by DRM, and provides many of the basic methods for working with
@@ -774,6 +817,68 @@ fn atomic_helper_check<S, D>(
})
}
+ /// Merge all frame-damage clips on this (new) plane state -- relative to `old` -- into a
+ /// single bounding rectangle, intersected with the plane's visible source area.
+ ///
+ /// Returns [`None`] when the plane is not visible or there is nothing to update. If the client
+ /// supplied no explicit damage clips, the full plane rectangle is returned, so a driver can
+ /// always treat [`Some`] as "repaint this rectangle" and fall back to a full-frame update.
+ /// Coordinates are integer pixels in the plane's source space.
+ ///
+ /// [`drm_atomic_helper_damage_merged`]: srctree/include/drm/drm_damage_helper.h
+ fn damage_merged(&self, old: &impl AsRawPlaneState) -> Option<Rect> {
+ let mut rect = bindings::drm_rect {
+ x1: 0,
+ y1: 0,
+ x2: 0,
+ y2: 0,
+ };
+
+ // SAFETY:
+ // - `old` and `self` are valid initialized `drm_plane_state`s via their type invariants.
+ // - `drm_atomic_helper_damage_merged` only reads the two states (to gather the damage
+ // clips and the source rectangle) and writes the merged result into `rect`; it does not
+ // mutate the plane state, so deriving a `*mut` from our shared reference is sound.
+ let visible = unsafe {
+ bindings::drm_atomic_helper_damage_merged(
+ core::ptr::from_ref(old.as_raw()),
+ core::ptr::from_ref(self.as_raw()).cast_mut(),
+ &mut rect,
+ )
+ };
+
+ visible.then(|| Rect::from_raw(&rect))
+ }
+
+ /// Invoke `f` once per frame-damage clip on this (new) plane state relative to `old`, each
+ /// intersected with the plane's visible source area -- i.e. the individual rectangles that
+ /// [`Self::damage_merged`] collapses into one. If the client supplied no explicit damage clips,
+ /// `f` is called once with the full plane rectangle. Coordinates are integer pixels in the
+ /// plane's source space.
+ ///
+ /// This lets a driver forward each changed region separately (e.g. to a remote display) instead
+ /// of the bounding box of them all.
+ ///
+ /// [`drm_atomic_helper_damage_iter`]: srctree/include/drm/drm_damage_helper.h
+ fn for_each_damage_clip(&self, old: &impl AsRawPlaneState, mut f: impl FnMut(Rect)) {
+ let mut iter = bindings::drm_atomic_helper_damage_iter::default();
+ let mut clip = bindings::drm_rect::default();
+ // SAFETY:
+ // - `old` and `self` are valid initialized `drm_plane_state`s via their type invariants.
+ // - `drm_atomic_helper_damage_iter_init` only reads the two states to set up `iter`, and
+ // `_next` only reads `iter` and writes `clip`; neither escapes a pointer.
+ unsafe {
+ bindings::drm_atomic_helper_damage_iter_init(
+ &mut iter,
+ core::ptr::from_ref(old.as_raw()),
+ core::ptr::from_ref(self.as_raw()),
+ );
+ while bindings::drm_atomic_helper_damage_iter_next(&mut iter, &mut clip) {
+ f(Rect::from_raw(&clip));
+ }
+ }
+ }
+
/// Return the framebuffer currently set for this plane state
#[inline]
fn framebuffer<D>(&self) -> Option<&Framebuffer<D>>
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 10/23] rust: drm: framebuffer: add validated shmem scanout views
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (8 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 9/23] rust: drm: kms: add plane damage-clip accessors Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 11/23] rust: drm: kms: expose checked plane geometry Mike Lothian
` (12 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, David Airlie, Simona Vetter,
Lyude Paul, linux-kernel, rust-for-linux
Add framebuffer geometry and reference-counting operations for drivers
that retain and inspect scanout buffers outside an atomic callback.
Build borrowed and owned adapters on the existing shmem VMap
implementation. The owned form retains the GEM object so a driver
can prepare and reuse a bounded scanout pool.
Constrain both adapters to the exact Rust shmem object type. Reject
foreign-device, imported, multiplane, non-linear, block-layout,
undersized, and invalid-pitch framebuffers. Apply the framebuffer
offset to the returned SysMem view with checked size arithmetic,
and add KUnit coverage for the validation rules.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/helpers/drm/drm.c | 1 +
rust/helpers/drm/framebuffer.c | 13 ++
rust/kernel/drm/fourcc.rs | 28 ++-
rust/kernel/drm/kms/framebuffer.rs | 345 ++++++++++++++++++++++++++++-
4 files changed, 382 insertions(+), 5 deletions(-)
create mode 100644 rust/helpers/drm/framebuffer.c
diff --git a/rust/helpers/drm/drm.c b/rust/helpers/drm/drm.c
index 45890e9c3290..2144a67623bd 100644
--- a/rust/helpers/drm/drm.c
+++ b/rust/helpers/drm/drm.c
@@ -3,6 +3,7 @@
#ifdef CONFIG_DRM
#ifdef CONFIG_DRM_KMS_HELPER
#include "atomic.c"
+#include "framebuffer.c"
#include "vblank.c"
#endif
diff --git a/rust/helpers/drm/framebuffer.c b/rust/helpers/drm/framebuffer.c
new file mode 100644
index 000000000000..672cee03463a
--- /dev/null
+++ b/rust/helpers/drm/framebuffer.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <drm/drm_framebuffer.h>
+
+__rust_helper void rust_helper_drm_framebuffer_get(struct drm_framebuffer *fb)
+{
+ drm_framebuffer_get(fb);
+}
+
+__rust_helper void rust_helper_drm_framebuffer_put(struct drm_framebuffer *fb)
+{
+ drm_framebuffer_put(fb);
+}
diff --git a/rust/kernel/drm/fourcc.rs b/rust/kernel/drm/fourcc.rs
index a30e40dbc037..010823c4c86c 100644
--- a/rust/kernel/drm/fourcc.rs
+++ b/rust/kernel/drm/fourcc.rs
@@ -12,9 +12,29 @@ const fn fourcc_code(a: u8, b: u8, c: u8, d: u8) -> u32 {
// TODO: We manually import this because we don't have a reasonable way of getting constants from
// function-like macros in bindgen yet.
pub(crate) const FORMAT_MOD_INVALID: u64 = 0xffffffffffffff;
+/// Linear framebuffer layout (`DRM_FORMAT_MOD_LINEAR`).
+pub(crate) const FORMAT_MOD_LINEAR: u64 = 0;
-// TODO: We need to automate importing all of these. For the time being, just add the single one
-// that we need
+/// 32 bpp RGB with unused alpha.
+pub const XRGB8888: u32 = fourcc_code(b'X', b'R', b'2', b'4');
-/// 32 bpp RGB
-pub const XRGB888: u32 = fourcc_code(b'X', b'R', b'2', b'4');
+/// 32 bpp RGB with alpha.
+pub const ARGB8888: u32 = fourcc_code(b'A', b'R', b'2', b'4');
+
+/// 32 bpp BGR with unused alpha.
+pub const XBGR8888: u32 = fourcc_code(b'X', b'B', b'2', b'4');
+
+/// 32 bpp BGR with alpha.
+pub const ABGR8888: u32 = fourcc_code(b'A', b'B', b'2', b'4');
+
+/// 30 bpp 10:10:10 RGB with unused alpha.
+pub const XRGB2101010: u32 = fourcc_code(b'X', b'R', b'3', b'0');
+
+/// 30 bpp 10:10:10 RGB with alpha.
+pub const ARGB2101010: u32 = fourcc_code(b'A', b'R', b'3', b'0');
+
+/// 30 bpp 10:10:10 BGR with unused alpha.
+pub const XBGR2101010: u32 = fourcc_code(b'X', b'B', b'3', b'0');
+
+/// 30 bpp 10:10:10 BGR with alpha.
+pub const ABGR2101010: u32 = fourcc_code(b'A', b'B', b'3', b'0');
diff --git a/rust/kernel/drm/kms/framebuffer.rs b/rust/kernel/drm/kms/framebuffer.rs
index 54d0391388a9..02e9e63cff30 100644
--- a/rust/kernel/drm/kms/framebuffer.rs
+++ b/rust/kernel/drm/kms/framebuffer.rs
@@ -5,8 +5,20 @@
//! C header: [`include/drm/drm_framebuffer.h`](srctree/include/drm/drm_framebuffer.h)
use super::{KmsDriver, ModeObject, Sealed};
-use crate::{drm::device::Device, types::*};
+use crate::{
+ drm::device::Device,
+ prelude::*,
+ sync::aref::{ARef, AlwaysRefCounted},
+ types::*,
+};
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+use crate::{
+ drm::gem::{self, shmem, BaseObject},
+ io::{IoBase, SysMem},
+};
use bindings;
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+use core::ops::Deref;
use core::{marker::*, ptr};
/// The main interface for [`struct drm_framebuffer`].
@@ -55,6 +67,145 @@ fn eq(&self, other: &Self) -> bool {
}
impl<T: KmsDriver> Eq for Framebuffer<T> {}
+// SAFETY: DRM framebuffers use the refcount in their embedded mode object. The C get/put helpers
+// operate on that refcount and release the object only after the last reference is dropped.
+unsafe impl<T: KmsDriver> AlwaysRefCounted for Framebuffer<T> {
+ fn inc_ref(&self) {
+ // SAFETY: A shared reference proves the framebuffer and its refcount are live.
+ unsafe { bindings::drm_framebuffer_get(self.0.get()) };
+ }
+
+ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
+ // SAFETY: The caller transfers one live framebuffer reference to this method.
+ unsafe { bindings::drm_framebuffer_put(obj.as_ref().0.get()) };
+ }
+}
+
+/// A validated packed, linear framebuffer mapping backed by Lyude's shmem [`shmem::VMap`].
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+pub struct FramebufferMapping<O, R>
+where
+ O: gem::DriverObject,
+ R: Deref<Target = shmem::Object<O>>,
+{
+ map: shmem::VMap<O, R>,
+ offset: usize,
+ len: usize,
+ pitch: usize,
+ width: u32,
+ height: u32,
+ format: u32,
+}
+
+/// A framebuffer mapping borrowed from its backing object.
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+pub type FramebufferVMap<'a, O> = FramebufferMapping<O, &'a shmem::Object<O>>;
+
+/// A framebuffer mapping which owns a reference to its backing object.
+///
+/// This is suitable for a bounded scanout-registration cache: dropping it releases the mapping and
+/// object reference, while retaining it keeps the validated CPU view stable across atomic commits.
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+pub type FramebufferVMapOwned<O> = FramebufferMapping<O, ARef<shmem::Object<O>>>;
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+struct PackedLayout {
+ offset: usize,
+ len: usize,
+ pitch: usize,
+}
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+fn packed_layout(raw: &bindings::drm_framebuffer, object_size: usize) -> Result<PackedLayout> {
+ if raw.format.is_null() {
+ return Err(EINVAL);
+ }
+
+ // SAFETY: The caller supplies a live framebuffer, whose format descriptor remains valid.
+ let format = unsafe { &*raw.format };
+ if format.num_planes != 1 || raw.modifier != crate::drm::fourcc::FORMAT_MOD_LINEAR {
+ return Err(EINVAL);
+ }
+
+ // Restrict this convenience adapter to ordinary packed scanlines. More complex block or tiled
+ // layouts need a layout-specific API instead of pretending to be a byte raster.
+ let block_width = unsafe { bindings::drm_format_info_block_width(raw.format, 0) };
+ let block_height = unsafe { bindings::drm_format_info_block_height(raw.format, 0) };
+ if block_width != 1 || block_height != 1 {
+ return Err(EINVAL);
+ }
+
+ let min_pitch =
+ usize::try_from(unsafe { bindings::drm_format_info_min_pitch(raw.format, 0, raw.width) })
+ .map_err(|_| EOVERFLOW)?;
+ let pitch = raw.pitches[0] as usize;
+ if pitch < min_pitch {
+ return Err(EINVAL);
+ }
+
+ let offset = raw.offsets[0] as usize;
+ let len = pitch.checked_mul(raw.height as usize).ok_or(EOVERFLOW)?;
+ let end = offset.checked_add(len).ok_or(EOVERFLOW)?;
+ if end > object_size {
+ return Err(EINVAL);
+ }
+
+ Ok(PackedLayout { offset, len, pitch })
+}
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+fn validate_object(
+ raw: &bindings::drm_framebuffer,
+ object: *mut bindings::drm_gem_object,
+) -> Result {
+ if object.is_null() {
+ return Err(EINVAL);
+ }
+ // SAFETY: The object is non-null and live while its framebuffer owns it.
+ let object = unsafe { &*object };
+ if object.dev != raw.dev || !object.import_attach.is_null() {
+ return Err(EINVAL);
+ }
+ Ok(())
+}
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+impl<O, R> FramebufferMapping<O, R>
+where
+ O: gem::DriverObject,
+ R: Deref<Target = shmem::Object<O>>,
+{
+ /// Return the offset-adjusted pixel storage as a system-memory I/O view.
+ pub fn view(&self) -> SysMem<'_, [u8]> {
+ let base = (&self.map).as_view().as_ptr().cast::<u8>();
+ // SAFETY: the mapping constructor checked `offset + len` against the object's size, and
+ // borrowing `self` keeps the owning VMap alive for the returned view.
+ let ptr = unsafe { core::ptr::slice_from_raw_parts_mut(base.add(self.offset), self.len) };
+ // SAFETY: The range above is mapped, kernel-accessible system memory for this borrow.
+ unsafe { SysMem::new(ptr) }
+ }
+
+ /// Return the validated line pitch in bytes.
+ pub fn pitch(&self) -> usize {
+ self.pitch
+ }
+
+ /// Return the visible width in pixels.
+ pub fn width(&self) -> u32 {
+ self.width
+ }
+
+ /// Return the visible height in pixels.
+ pub fn height(&self) -> u32 {
+ self.height
+ }
+
+ /// Return the DRM fourcc pixel format.
+ pub fn format(&self) -> u32 {
+ self.format
+ }
+}
+
impl<T: KmsDriver> Framebuffer<T> {
/// Convert a raw pointer to a `struct drm_framebuffer` into a [`Framebuffer`]
///
@@ -67,4 +218,196 @@ pub(super) unsafe fn from_raw<'a>(ptr: *const bindings::drm_framebuffer) -> &'a
// SAFETY: Our data layout is identical to drm_framebuffer
unsafe { &*ptr.cast() }
}
+
+ /// Return an owned reference to this framebuffer.
+ pub fn to_aref(&self) -> ARef<Self> {
+ self.into()
+ }
+
+ /// Return the framebuffer width in pixels.
+ pub fn width(&self) -> u32 {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ unsafe { (*self.0.get()).width }
+ }
+
+ /// Return the framebuffer height in pixels.
+ pub fn height(&self) -> u32 {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ unsafe { (*self.0.get()).height }
+ }
+
+ /// Return the framebuffer's DRM fourcc pixel format.
+ pub fn format(&self) -> u32 {
+ // SAFETY: An initialized framebuffer has a valid format descriptor.
+ unsafe { (*(*self.0.get()).format).format }
+ }
+
+ /// Return the pitch for `plane`, rejecting indices outside the format's actual plane count.
+ pub fn pitch(&self, plane: usize) -> Result<u32> {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ let raw = unsafe { &*self.0.get() };
+ if raw.format.is_null() {
+ return Err(EINVAL);
+ }
+ // SAFETY: `format` is non-null and remains valid for the framebuffer's lifetime.
+ if plane >= unsafe { (*raw.format).num_planes as usize } || plane >= raw.pitches.len() {
+ return Err(EINVAL);
+ }
+ Ok(raw.pitches[plane])
+ }
+
+ /// Map a packed, single-plane, linear Rust shmem framebuffer.
+ ///
+ /// The returned view starts at the framebuffer plane's declared offset rather than the start
+ /// of the GEM object. Multi-plane, imported, non-linear, block-compressed, undersized and
+ /// cross-device objects are rejected.
+ #[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+ pub fn vmap<O>(&self) -> Result<FramebufferVMap<'_, O>>
+ where
+ O: gem::DriverObject<Driver = T>,
+ T: crate::drm::Driver<Object = shmem::Object<O>>,
+ {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ let raw = unsafe { &*self.0.get() };
+ let object_raw = raw.obj[0];
+ validate_object(raw, object_raw)?;
+
+ // SAFETY:
+ // - `T::Object` is exactly `shmem::Object<O>` by the associated-type bound above.
+ // - `validate_object` checked that this is a local, non-imported object owned by this
+ // framebuffer's instance of `T`.
+ // - The framebuffer keeps its backing object alive for this borrow.
+ let object = unsafe { <shmem::Object<O> as gem::IntoGEMObject>::from_raw(object_raw) };
+ let layout = packed_layout(raw, object.size())?;
+
+ Ok(FramebufferMapping {
+ map: object.vmap()?,
+ offset: layout.offset,
+ len: layout.len,
+ pitch: layout.pitch,
+ width: raw.width,
+ height: raw.height,
+ // SAFETY: `packed_layout` rejected a null format pointer above.
+ format: unsafe { (*raw.format).format },
+ })
+ }
+
+ /// Returns the GEM object backing plane 0 of this framebuffer.
+ ///
+ /// A driver needs this to hand the buffer to a client, which is done by minting a handle for it
+ /// in that client's file. The same type, ownership, import and device checks as [`Self::vmap`]
+ /// apply, so the returned reference is known to belong to this driver.
+ #[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+ pub fn object<O>(&self) -> Result<&shmem::Object<O>>
+ where
+ O: gem::DriverObject<Driver = T>,
+ T: crate::drm::Driver<Object = shmem::Object<O>>,
+ {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ let raw = unsafe { &*self.0.get() };
+ let object_raw = raw.obj[0];
+ validate_object(raw, object_raw)?;
+
+ // SAFETY: `validate_object` established that `object_raw` is a live object of this
+ // driver's type, and it is owned by the framebuffer for at least this borrow.
+ Ok(unsafe { <shmem::Object<O> as gem::IntoGEMObject>::from_raw(object_raw) })
+ }
+
+ /// Map a packed, single-plane, linear Rust shmem framebuffer and retain its backing object.
+ ///
+ /// The validation is identical to [`Framebuffer::vmap`], but the returned mapping is not tied
+ /// to this framebuffer borrow. It can therefore be retained in a bounded prepared-scanout
+ /// cache and reused by later commits. The mapping itself keeps the GEM object alive.
+ #[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+ pub fn owned_vmap<O>(&self) -> Result<FramebufferVMapOwned<O>>
+ where
+ O: gem::DriverObject<Driver = T>,
+ T: crate::drm::Driver<Object = shmem::Object<O>>,
+ {
+ // SAFETY: The framebuffer is initialized via its type invariant.
+ let raw = unsafe { &*self.0.get() };
+ let object_raw = raw.obj[0];
+ validate_object(raw, object_raw)?;
+
+ // SAFETY: The same type, ownership, import, and device checks as `vmap` hold here. The
+ // returned VMap takes its own object reference before this framebuffer borrow can end.
+ let object = unsafe { <shmem::Object<O> as gem::IntoGEMObject>::from_raw(object_raw) };
+ let layout = packed_layout(raw, object.size())?;
+
+ Ok(FramebufferMapping {
+ map: object.owned_vmap()?,
+ offset: layout.offset,
+ len: layout.len,
+ pitch: layout.pitch,
+ width: raw.width,
+ height: raw.height,
+ // SAFETY: `packed_layout` rejected a null format pointer above.
+ format: unsafe { (*raw.format).format },
+ })
+ }
+}
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+#[kunit_tests(rust_drm_framebuffer)]
+mod tests {
+ use super::*;
+
+ fn linear_fb(width: u32, height: u32, pitch: u32, offset: u32) -> bindings::drm_framebuffer {
+ let mut fb = bindings::drm_framebuffer::default();
+ // SAFETY: `XRGB8888` is a valid DRM fourcc and the returned descriptor has static lifetime.
+ fb.format = unsafe { bindings::drm_format_info(crate::drm::fourcc::XRGB8888) };
+ fb.modifier = crate::drm::fourcc::FORMAT_MOD_LINEAR;
+ fb.width = width;
+ fb.height = height;
+ fb.pitches[0] = pitch;
+ fb.offsets[0] = offset;
+ fb
+ }
+
+ #[test]
+ fn packed_layout_honours_nonzero_offset() -> Result {
+ let fb = linear_fb(4, 2, 16, 128);
+ let layout = packed_layout(&fb, 160)?;
+ assert_eq!(layout.offset, 128);
+ assert_eq!(layout.len, 32);
+ Ok(())
+ }
+
+ #[test]
+ fn packed_layout_rejects_too_small_object() {
+ let fb = linear_fb(4, 2, 16, 128);
+ assert!(packed_layout(&fb, 159).is_err());
+ }
+
+ #[test]
+ fn packed_layout_rejects_multiple_planes() {
+ let mut fb = linear_fb(4, 2, 16, 0);
+ // SAFETY: `linear_fb` stored a non-null static format descriptor.
+ let mut format = unsafe { *fb.format };
+ format.num_planes = 2;
+ fb.format = &raw const format;
+ assert!(packed_layout(&fb, 32).is_err());
+ }
+
+ #[test]
+ fn imported_object_is_rejected() {
+ let mut fb = linear_fb(4, 2, 16, 0);
+ let dev = ptr::NonNull::<bindings::drm_device>::dangling().as_ptr();
+ fb.dev = dev;
+ let mut object = bindings::drm_gem_object::default();
+ object.dev = dev;
+ object.import_attach = ptr::NonNull::<bindings::dma_buf_attachment>::dangling().as_ptr();
+ assert!(validate_object(&fb, &raw mut object).is_err());
+ }
+
+ #[test]
+ fn cross_device_object_is_rejected() {
+ let mut first = core::mem::MaybeUninit::<bindings::drm_device>::uninit();
+ let mut second = core::mem::MaybeUninit::<bindings::drm_device>::uninit();
+ let mut fb = linear_fb(4, 2, 16, 0);
+ fb.dev = first.as_mut_ptr();
+ let mut object = bindings::drm_gem_object::default();
+ object.dev = second.as_mut_ptr();
+ assert!(validate_object(&fb, &raw mut object).is_err());
+ }
}
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 11/23] rust: drm: kms: expose checked plane geometry
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (9 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 10/23] rust: drm: framebuffer: add validated shmem scanout views Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 12/23] rust: drm: kms: add owned CRTC and vblank references Mike Lothian
` (11 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Expose the requested source rectangle and the visibility and clipped
rectangles produced by drm_atomic_helper_check_plane_state().
Keep 16.16 source coordinates explicit at the raw-state
boundary. Convert helper-clipped source coordinates to integer pixels
only after rejecting negative or fractional values, and return the
clipped destination in CRTC coordinates.
These generic accessors let Rust KMS drivers implement cursor
clipping and validate full-frame scanout without reaching into
generated bindings.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/plane.rs | 59 ++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 3bff4091abb2..bc830503b142 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -758,6 +758,65 @@ fn crtc_h(&self) -> u32 {
self.as_raw().crtc_h
}
+ /// Return the requested source X coordinate in 16.16 fixed-point pixels.
+ fn source_x_16_16(&self) -> u32 {
+ self.as_raw().src_x
+ }
+
+ /// Return the requested source Y coordinate in 16.16 fixed-point pixels.
+ fn source_y_16_16(&self) -> u32 {
+ self.as_raw().src_y
+ }
+
+ /// Return the requested source width in 16.16 fixed-point pixels.
+ fn source_width_16_16(&self) -> u32 {
+ self.as_raw().src_w
+ }
+
+ /// Return the requested source height in 16.16 fixed-point pixels.
+ fn source_height_16_16(&self) -> u32 {
+ self.as_raw().src_h
+ }
+
+ /// Return whether [`Self::atomic_helper_check`] found any visible part of the plane.
+ fn visible(&self) -> bool {
+ self.as_raw().visible
+ }
+
+ /// Return the helper-clipped source rectangle in integer framebuffer pixels.
+ ///
+ /// This is valid after [`Self::atomic_helper_check`]. Fractional source coordinates are
+ /// rejected with [`EINVAL`].
+ fn visible_source(&self) -> Result<Option<Rect>> {
+ if !self.visible() {
+ return Ok(None);
+ }
+
+ let src = &self.as_raw().src;
+ if src.x1 < 0
+ || src.y1 < 0
+ || src.x2 < 0
+ || src.y2 < 0
+ || (src.x1 | src.y1 | src.x2 | src.y2) & 0xffff != 0
+ {
+ return Err(EINVAL);
+ }
+
+ Ok(Some(Rect {
+ x1: src.x1 >> 16,
+ y1: src.y1 >> 16,
+ x2: src.x2 >> 16,
+ y2: src.y2 >> 16,
+ }))
+ }
+
+ /// Return the helper-clipped destination rectangle in CRTC pixels.
+ ///
+ /// This is valid after [`Self::atomic_helper_check`].
+ fn visible_destination(&self) -> Option<Rect> {
+ self.visible().then(|| Rect::from_raw(&self.as_raw().dst))
+ }
+
/// The plane's rotation/reflection (`DRM_MODE_ROTATE_*` | `DRM_MODE_REFLECT_*` bitmask), for a
/// plane with a rotation property (see
/// [`UnregisteredPlane::create_rotation_property`]). Defaults to `DRM_MODE_ROTATE_0`.
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 12/23] rust: drm: kms: add owned CRTC and vblank references
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (10 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 11/23] rust: drm: kms: expose checked plane geometry Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 13/23] rust: drm: kms: plane: add FB_DAMAGE_CLIPS property support Mike Lothian
` (10 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
`&Crtc<T>` is only valid for the callback DRM handed it to, and
`VblankRef` borrows one. That does not fit two common shapes:
- a driver that enables vblanks in `atomic_enable` and releases
them in
`atomic_disable` holds the reference across two callbacks,
so it has to `mem::forget` the guard and hand-balance a raw
`drm_crtc_vblank_put`;
- a driver with a software vblank clock must reach its CRTC from
a timer
callback, so it stashes a raw `drm_crtc` pointer and calls
`drm_crtc_handle_vblank` on it.
Both are safe in principle -- mode objects live until their DRM device
is freed -- but neither can be expressed, so drivers reintroduce raw
pointers that the safe KMS API exists to remove.
Add `CrtcRef`, an owned handle holding an `ARef` to the DRM device,
which keeps the CRTC alive and hands back a `&Crtc<T>` from any context,
and `OwnedVblankRef`, a vblank reference built on it and obtained by
converting a `VblankRef` with `into_owned()`. The vblank reference
is still released exactly once, on drop.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/crtc.rs | 54 +++++++++++++++++++++++++++++++++++
rust/kernel/drm/kms/vblank.rs | 47 ++++++++++++++++++++++++++++++
2 files changed, 101 insertions(+)
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index a7024d8921ca..892f04f04e22 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -14,6 +14,7 @@
drm::device::Device,
error::{from_result, to_result},
prelude::*,
+ sync::aref::ARef,
types::{NotThreadSafe, Opaque},
};
use core::{
@@ -304,6 +305,59 @@ pub(crate) fn get_vblank_ptr(&self) -> *mut bindings::drm_vblank_crtc {
pub(crate) const fn has_vblank() -> bool {
T::OPS.funcs.enable_vblank.is_some()
}
+
+ /// Returns an owned handle to this [`Crtc`].
+ ///
+ /// A `&Crtc<T>` is only valid for the callback that produced it. Drivers that must reach a
+ /// CRTC from a context DRM did not hand one to -- a timer callback driving a software vblank
+ /// clock, for instance -- can keep a [`CrtcRef`] instead of stashing a raw pointer.
+ pub fn to_owned_ref(&self) -> CrtcRef<T> {
+ CrtcRef {
+ dev: self.drm_dev().into(),
+ crtc: NonNull::from(self),
+ }
+ }
+}
+
+/// An owned handle to a [`Crtc`].
+///
+/// Mode objects are owned by their DRM device and live until it is freed, so holding an [`ARef`] to
+/// that device is enough to keep the CRTC valid. [`crtc`](CrtcRef::crtc) then hands back a usable
+/// reference from any context.
+///
+/// [`ARef`]: crate::sync::aref::ARef
+pub struct CrtcRef<T: DriverCrtc> {
+ /// Keeps the DRM device -- and with it every mode object it owns, including `crtc` -- alive.
+ dev: ARef<Device<T::Driver>>,
+ crtc: NonNull<Crtc<T>>,
+}
+
+// SAFETY: This is an owning handle to device state, not to anything thread-local, and the
+// `ARef` it holds is itself `Send`.
+unsafe impl<T: DriverCrtc> Send for CrtcRef<T> {}
+
+// SAFETY: The only shared access offered is `crtc()`, which yields the same `&Crtc<T>` that is
+// already freely shareable between threads.
+unsafe impl<T: DriverCrtc> Sync for CrtcRef<T> {}
+
+impl<T: DriverCrtc> CrtcRef<T> {
+ /// The [`Crtc`] this handle refers to.
+ pub fn crtc(&self) -> &Crtc<T> {
+ // SAFETY: `self.dev` holds a reference to the DRM device that owns this CRTC, and mode
+ // objects live until their device is freed, so the pointer is still valid.
+ unsafe { self.crtc.as_ref() }
+ }
+
+ /// The DRM device that owns the [`Crtc`].
+ pub fn drm_dev(&self) -> &Device<T::Driver> {
+ &self.dev
+ }
+}
+
+impl<T: DriverCrtc> Clone for CrtcRef<T> {
+ fn clone(&self) -> Self {
+ self.crtc().to_owned_ref()
+ }
}
/// A [`Crtc`] that has not yet been registered with userspace.
diff --git a/rust/kernel/drm/kms/vblank.rs b/rust/kernel/drm/kms/vblank.rs
index a725a46110d8..672968c1d3cb 100644
--- a/rust/kernel/drm/kms/vblank.rs
+++ b/rust/kernel/drm/kms/vblank.rs
@@ -359,6 +359,53 @@ fn new(crtc: &'a Crtc<T>) -> Result<Self> {
Ok(Self(crtc))
}
+
+ /// Converts this reference into an [`OwnedVblankRef`], which is not tied to the borrow of the
+ /// [`Crtc`] it came from.
+ pub fn into_owned(self) -> OwnedVblankRef<T> {
+ let crtc = self.0;
+
+ // The new owner takes over the reference this guard was holding.
+ mem::forget(self);
+
+ OwnedVblankRef(crtc.to_owned_ref())
+ }
+}
+
+/// A vblank reference that owns a reference to its DRM device.
+///
+/// [`VblankRef`] borrows the [`Crtc`] it was taken from, so it cannot outlive the callback that
+/// created it. A driver whose vblank interval spans several callbacks -- typically one that enables
+/// vblanks in [`atomic_enable`] and releases them in [`atomic_disable`], or that drives a software
+/// vblank clock from a timer -- needs a reference it can store instead.
+///
+/// It wraps a [`CrtcRef`], which keeps the DRM device -- and so the CRTC -- alive, so [`crtc`]
+/// hands back a usable reference for as long as this object exists. Dropping it releases the
+/// vblank reference exactly once.
+///
+/// [`atomic_enable`]: DriverCrtc::atomic_enable
+/// [`atomic_disable`]: DriverCrtc::atomic_disable
+/// [`crtc`]: OwnedVblankRef::crtc
+pub struct OwnedVblankRef<T: VblankDriverCrtc>(CrtcRef<T>);
+
+impl<T: VblankDriverCrtc> OwnedVblankRef<T> {
+ /// The [`Crtc`] whose vblanks this reference is keeping enabled.
+ pub fn crtc(&self) -> &Crtc<T> {
+ self.0.crtc()
+ }
+
+ /// The DRM device that owns the [`Crtc`].
+ pub fn drm_dev(&self) -> &Device<T::Driver> {
+ self.0.drm_dev()
+ }
+}
+
+impl<T: VblankDriverCrtc> Drop for OwnedVblankRef<T> {
+ fn drop(&mut self) {
+ // SAFETY: `crtc()` returns a valid, initialized `drm_crtc`, and this type holds exactly
+ // one vblank reference -- taken by `VblankRef::new()` and transferred by `into_owned()`.
+ unsafe { bindings::drm_crtc_vblank_put(self.crtc().as_raw()) };
+ }
}
/// The base wrapper for [`drm_vblank_crtc`].
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 13/23] rust: drm: kms: plane: add FB_DAMAGE_CLIPS property support
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (11 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 12/23] rust: drm: kms: add owned CRTC and vblank references Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 14/23] rust: drm: add a safe constructor for owned registration data Mike Lothian
` (9 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Userspace can only hand a driver the rectangles that actually changed
between two framebuffers if the plane advertises the FB_DAMAGE_CLIPS
property. Without it a compositor supplies nothing, and unchanged
commits are indistinguishable from missing damage information --
which forces a driver either to freeze or to re-send whole frames.
That matters most for drivers uploading their scanout over a slow link.
Wrap `drm_plane_enable_fb_damage_clips()` so a plane can attach
the property before registration, alongside the existing rotation
property helper.
The consumer is the vino DisplayLink driver, which encodes and sends
only the changed strips of each frame over USB.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/plane.rs | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index bc830503b142..62de8a1dad19 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -438,6 +438,27 @@ pub fn create_rotation_property(
)
})
}
+
+ /// Attaches the `FB_DAMAGE_CLIPS` property to this plane.
+ ///
+ /// Userspace can then hand the driver the list of rectangles that actually changed between two
+ /// framebuffers, instead of leaving it to infer damage from a buffer swap. Drivers that upload
+ /// their scanout over a slow link -- USB display adapters especially -- need this to send only
+ /// the changed regions.
+ ///
+ /// Without the property attached, a compositor cannot supply clips at all: unchanged commits
+ /// arrive with an empty list, which is indistinguishable from "no damage information".
+ ///
+ /// The clips are read back through
+ /// [`RawPlaneState::damage_clips`](crate::drm::kms::plane::RawPlaneState::damage_clips).
+ ///
+ /// Call this during [`KmsDriver::create_objects`](crate::drm::kms::KmsDriver::create_objects),
+ /// before the device is registered.
+ pub fn enable_fb_damage_clips(&self) {
+ // SAFETY: `as_raw()` is a valid, not-yet-registered plane; attaching a property before
+ // registration is exactly what this helper is for.
+ unsafe { bindings::drm_plane_enable_fb_damage_clips(self.as_raw()) }
+ }
}
/// A trait implemented by any type that acts as a [`struct drm_plane`] interface.
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 14/23] rust: drm: add a safe constructor for owned registration data
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (12 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 13/23] rust: drm: kms: plane: add FB_DAMAGE_CLIPS property support Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 15/23] rust: drm: pin the owner while DRM files remain open Mike Lothian
` (8 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, rust-for-linux, linux-kernel
A DRM registration whose associated data is 'static cannot outlive any
references held by that data. Add a safe constructor for this common
case so drivers do not have to promise manually that their registration
will never be forgotten.
Keep the existing unsafe constructor for registration data which
genuinely borrows from the bus binding.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/driver.rs | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 356be329a2b6..2e7987a71a7a 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -169,7 +169,8 @@ pub struct Registration<'a, T: Driver> {
}
impl<'a, T: Driver> Registration<'a, T> {
- /// Register a new [`UnregisteredDevice`](drm::UnregisteredDevice) with userspace.
+ /// Registers a new [`UnregisteredDevice`](drm::UnregisteredDevice) with borrowed
+ /// registration data.
///
/// # Safety
///
@@ -177,7 +178,7 @@ impl<'a, T: Driver> Registration<'a, T> {
/// [`Drop`] implementation from running, since the registration data may contain borrowed
/// references that become invalid after `'a` ends.
pub unsafe fn new<E>(
- dev: &'a device::Device<device::Bound>,
+ dev: &device::Device<device::Bound>,
drm: drm::UnregisteredDevice<T>,
reg_data: impl PinInit<T::RegistrationData<'a>, E>,
flags: usize,
@@ -243,6 +244,29 @@ pub fn device(&self) -> &drm::Device<T> {
}
}
+impl<T: Driver> Registration<'static, T> {
+ /// Registers a new [`UnregisteredDevice`](drm::UnregisteredDevice) with owned registration
+ /// data.
+ ///
+ /// Unlike [`Registration::new`], this constructor is safe because its registration
+ /// data cannot contain non-static references. Forgetting the returned registration can leak
+ /// the DRM device and its parent reference, but cannot leave a live registration referring to
+ /// expired data.
+ pub fn new_static<E>(
+ dev: &device::Device<device::Bound>,
+ drm: drm::UnregisteredDevice<T>,
+ reg_data: impl PinInit<T::RegistrationData<'static>, E>,
+ flags: usize,
+ ) -> Result<Self>
+ where
+ Error: From<E>,
+ {
+ // SAFETY: `RegistrationData<'static>` cannot borrow data that expires while a forgotten
+ // registration remains accessible.
+ unsafe { Self::new(dev, drm, reg_data, flags) }
+ }
+}
+
// SAFETY: `Registration` doesn't offer any methods or access to fields when shared between
// threads, hence it's safe to share it.
unsafe impl<T: Driver> Sync for Registration<'_, T> {}
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 15/23] rust: drm: pin the owner while DRM files remain open
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (13 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 14/23] rust: drm: add a safe constructor for owned registration data Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 16/23] rust: drm: kms: add the plane blend-mode property Mike Lothian
` (7 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Mukesh Kumar Chaurasiya (IBM),
Asahi Lina, rust-for-linux, linux-kernel
Give each Rust DRM device its own driver and file-operations tables
so file_operations::owner can identify the module that owns the
implementation. Open DRM file descriptors then hold the same module
reference that C DRM drivers receive through DEFINE_DRM_GEM_*_FOPS().
Pass the owning module to UnregisteredDevice::new() and use the
built-in null module for the shmem KUnit device.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/device.rs | 46 ++++++++++++++++++++++++++++++++++--
rust/kernel/drm/gem/shmem.rs | 8 ++++++-
2 files changed, 51 insertions(+), 3 deletions(-)
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index bc2cdcd2b695..efbec3f42bda 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -208,9 +208,14 @@ const fn compute_features() -> u32 {
/// Create a new `UnregisteredDevice` for a `drm::Driver`.
///
/// This can be used to create a [`Registration`](kernel::drm::Registration).
+ ///
+ /// `module` must be the module that owns the driver implementation, i.e. `&THIS_MODULE`. It is
+ /// stamped into this device's `file_operations::owner` so that an open `/dev/dri/cardN` file
+ /// descriptor pins the module, exactly as `DEFINE_DRM_GEM_*_FOPS()` does in C.
pub fn new(
dev: &T::ParentDevice<device::Bound>,
data: impl PinInit<T::Data, Error>,
+ module: &'static ThisModule,
) -> Result<Self> {
// `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
// compatible `Layout`.
@@ -253,8 +258,37 @@ pub fn new(
unsafe { bindings::drm_dev_put(drm_dev) };
})?;
- // SAFETY: `drm_dev` is still private to this function.
- unsafe { (*drm_dev).driver = const { &Self::VTABLE } };
+ // Give this device its own `file_operations`/`drm_driver` pair so that the owning module
+ // can be stamped into the fops. `fops->owner` is what makes `fops_get()` in
+ // `drm_stub_open()` take a module reference for every open DRM file: without it nothing
+ // pins the module, and unloading the driver while a compositor still has
+ // `/dev/dri/cardN` in a poll set frees the `file_operations` out from under
+ // `do_sys_poll()`, which then faults on `f_op->poll`.
+ //
+ // SAFETY: `raw_drm` is a valid pointer to `Self`, still private to this function, and
+ // both fields are plain data that need no drop.
+ let raw_fops = unsafe { Opaque::cast_into(ptr::addr_of!((*raw_drm.as_ptr()).fops)) };
+ // SAFETY: `raw_fops` is valid, aligned and points at uninitialized memory we own.
+ unsafe {
+ raw_fops.write(bindings::file_operations {
+ owner: module.as_ptr(),
+ ..Self::GEM_FOPS
+ })
+ };
+
+ // SAFETY: as above, for the per-device `drm_driver` copy.
+ let raw_vtable = unsafe { Opaque::cast_into(ptr::addr_of!((*raw_drm.as_ptr()).vtable)) };
+ // SAFETY: `raw_vtable` is valid, aligned and points at uninitialized memory we own.
+ unsafe {
+ raw_vtable.write(bindings::drm_driver {
+ fops: raw_fops,
+ ..Self::VTABLE
+ })
+ };
+
+ // SAFETY: `drm_dev` is still private to this function; `raw_vtable` lives inside the DRM
+ // device allocation and so outlives every use of `drm_device::driver`.
+ unsafe { (*drm_dev).driver = raw_vtable };
// SAFETY: `raw_drm` is valid; no concurrent access before registration.
unsafe { (*raw_drm.as_ptr()).registration_data = UnsafeCell::new(NonNull::dangling()) };
@@ -277,12 +311,20 @@ pub fn new(
///
/// * `self.dev` is a valid instance of a `struct device`.
/// * The data layout of `Self` remains the same across all implementations of `C`.
+/// * `self.vtable` and `self.fops` are initialized before the device is registered and are never
+/// mutated afterwards; `self.dev.driver` points at `self.vtable`, whose `fops` points at
+/// `self.fops`.
/// * Any invariants for `C` also apply.
#[repr(C)]
pub struct Device<T: drm::Driver, C: DeviceContext = Normal> {
dev: Opaque<bindings::drm_device>,
data: T::Data,
pub(super) registration_data: UnsafeCell<NonNull<T::RegistrationData<'static>>>,
+ /// Per-device copy of the driver vtable, so that `fops` below can be referenced from it.
+ vtable: Opaque<bindings::drm_driver>,
+ /// Per-device copy of the DRM file operations, carrying the owning module in `owner` so that
+ /// an open DRM file descriptor pins the module.
+ fops: Opaque<bindings::file_operations>,
_ctx: PhantomData<C>,
}
diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs
index 86797ab39ffd..8751000c92bb 100644
--- a/rust/kernel/drm/gem/shmem.rs
+++ b/rust/kernel/drm/gem/shmem.rs
@@ -642,12 +642,18 @@ impl drm::Driver for KunitDriver {
const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor] = &[];
}
+ // These tests only ever build into the kernel image, so there is no module to pin. A null
+ // `file_operations::owner` is exactly what a built-in driver uses.
+ //
+ // SAFETY: `NULL` is the correct `THIS_MODULE` for built-in code.
+ static KUNIT_MODULE: ThisModule = unsafe { ThisModule::from_ptr(ptr::null_mut()) };
+
fn create_drm_dev() -> Result<(faux::Registration, UnregisteredDevice<KunitDriver>)> {
// Create a faux DRM device so we can test gem object creation.
let data = try_pin_init!(KunitData {});
let reg = faux::Registration::new(c"Kunit", None)?;
let fdev = reg.as_ref();
- let drm = UnregisteredDevice::new(fdev, data)?;
+ let drm = UnregisteredDevice::new(fdev, data, &KUNIT_MODULE)?;
Ok((reg, drm))
}
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 16/23] rust: drm: kms: add the plane blend-mode property
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (14 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 15/23] rust: drm: pin the owner while DRM files remain open Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 17/23] rust: drm: add an owned display mode constructor Mike Lothian
` (6 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Expose drm_plane_create_blend_mode_property() so Rust KMS drivers
advertising alpha formats can declare how userspace should interpret
the alpha channel.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/plane.rs | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 62de8a1dad19..f148aed812f2 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -459,6 +459,22 @@ pub fn enable_fb_damage_clips(&self) {
// registration is exactly what this helper is for.
unsafe { bindings::drm_plane_enable_fb_damage_clips(self.as_raw()) }
}
+
+ /// Attaches the `pixel blend mode` property to this plane.
+ ///
+ /// `supported_modes` is a bitmask of `BIT(DRM_MODE_BLEND_*)`; `DRM_MODE_BLEND_PREMULTI` must
+ /// always be included. Any plane that advertises a pixel format with an alpha channel is
+ /// required to have this property -- `drm_mode_config_validate()` `WARN`s at registration
+ /// otherwise, because userspace has no way to know how the alpha will be interpreted.
+ ///
+ /// Call this during [`KmsDriver::create_objects`](crate::drm::kms::KmsDriver::create_objects),
+ /// before the device is registered.
+ pub fn create_blend_mode_property(&self, supported_modes: BlendModes) -> Result {
+ // SAFETY: `as_raw()` is a valid, not-yet-registered plane.
+ to_result(unsafe {
+ bindings::drm_plane_create_blend_mode_property(self.as_raw(), supported_modes.bits())
+ })
+ }
}
/// A trait implemented by any type that acts as a [`struct drm_plane`] interface.
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 17/23] rust: drm: add an owned display mode constructor
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (15 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 16/23] rust: drm: kms: add the plane blend-mode property Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 18/23] rust: drm: expose mode flags and CTA VIC matching Mike Lothian
` (5 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Add a safe constructor for standalone display modes used by drivers
and tests.
Accept the essential timing fields and reject invalid active, sync,
and total ordering before exposing the owned mode.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/modes.rs | 62 +++++++++++++++++++++++++++++++++++-
1 file changed, 61 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/drm/kms/modes.rs b/rust/kernel/drm/kms/modes.rs
index cc3c486eecf1..b48a02edfc13 100644
--- a/rust/kernel/drm/kms/modes.rs
+++ b/rust/kernel/drm/kms/modes.rs
@@ -6,7 +6,33 @@
use bindings;
-use crate::types::Opaque;
+use crate::{
+ error::{code::EINVAL, Result},
+ types::Opaque,
+};
+
+/// The essential timing fields of a display mode.
+#[derive(Clone, Copy)]
+pub struct ModeTimings {
+ /// Pixel clock in kHz.
+ pub clock_khz: i32,
+ /// Horizontal active pixels.
+ pub hdisplay: u16,
+ /// Start of the horizontal sync pulse.
+ pub hsync_start: u16,
+ /// End of the horizontal sync pulse.
+ pub hsync_end: u16,
+ /// Total horizontal pixels including blanking.
+ pub htotal: u16,
+ /// Vertical active lines.
+ pub vdisplay: u16,
+ /// Start of the vertical sync pulse.
+ pub vsync_start: u16,
+ /// End of the vertical sync pulse.
+ pub vsync_end: u16,
+ /// Total vertical lines including blanking.
+ pub vtotal: u16,
+}
/// DRM kernel-internal display mode structure.
///
@@ -30,6 +56,40 @@ unsafe impl Send for DisplayMode {}
unsafe impl Sync for DisplayMode {}
impl DisplayMode {
+ /// Creates a standalone display mode from validated timings.
+ ///
+ /// This is useful when a driver needs an owned mode for validation or tests rather than a
+ /// reference to a mode owned by the DRM core.
+ pub fn from_timings(t: ModeTimings) -> Result<Self> {
+ if t.clock_khz <= 0
+ || t.hdisplay == 0
+ || t.hdisplay > t.hsync_start
+ || t.hsync_start > t.hsync_end
+ || t.hsync_end > t.htotal
+ || t.vdisplay == 0
+ || t.vdisplay > t.vsync_start
+ || t.vsync_start > t.vsync_end
+ || t.vsync_end > t.vtotal
+ {
+ return Err(EINVAL);
+ }
+
+ let mut mode = bindings::drm_display_mode::default();
+ mode.clock = t.clock_khz;
+ mode.hdisplay = t.hdisplay;
+ mode.hsync_start = t.hsync_start;
+ mode.hsync_end = t.hsync_end;
+ mode.htotal = t.htotal;
+ mode.vdisplay = t.vdisplay;
+ mode.vsync_start = t.vsync_start;
+ mode.vsync_end = t.vsync_end;
+ mode.vtotal = t.vtotal;
+
+ Ok(Self {
+ inner: Opaque::new(mode),
+ })
+ }
+
/// Convert a raw pointer to a `struct drm_display_mode` into an immutable [`DisplayMode`] ref.
///
/// # SAFETY
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 18/23] rust: drm: expose mode flags and CTA VIC matching
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (16 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 17/23] rust: drm: add an owned display mode constructor Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 19/23] rust: drm: expose CRTC mode changes Mike Lothian
` (4 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Let Rust DRM drivers construct modes with signal flags, inspect those
flags, and use the DRM EDID helper to identify the matching CTA-861
Video Identification Code. This keeps drivers from duplicating the
canonical HDMI mode table.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/modes.rs | 73 ++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)
diff --git a/rust/kernel/drm/kms/modes.rs b/rust/kernel/drm/kms/modes.rs
index b48a02edfc13..584f20456c07 100644
--- a/rust/kernel/drm/kms/modes.rs
+++ b/rust/kernel/drm/kms/modes.rs
@@ -11,6 +11,60 @@
types::Opaque,
};
+/// Flags describing signal polarity and scan format for a display mode.
+///
+/// These correspond to the `DRM_MODE_FLAG_*` values accepted by the DRM mode helpers.
+#[derive(Clone, Copy, Default, PartialEq, Eq)]
+pub struct ModeFlags(u32);
+
+impl ModeFlags {
+ /// Horizontal sync is active high.
+ pub const PHSYNC: Self = Self(bindings::DRM_MODE_FLAG_PHSYNC);
+ /// Horizontal sync is active low.
+ pub const NHSYNC: Self = Self(bindings::DRM_MODE_FLAG_NHSYNC);
+ /// Vertical sync is active high.
+ pub const PVSYNC: Self = Self(bindings::DRM_MODE_FLAG_PVSYNC);
+ /// Vertical sync is active low.
+ pub const NVSYNC: Self = Self(bindings::DRM_MODE_FLAG_NVSYNC);
+ /// The mode is interlaced.
+ pub const INTERLACE: Self = Self(bindings::DRM_MODE_FLAG_INTERLACE);
+ /// The mode uses doublescan.
+ pub const DBLSCAN: Self = Self(bindings::DRM_MODE_FLAG_DBLSCAN);
+ /// The mode uses composite sync.
+ pub const CSYNC: Self = Self(bindings::DRM_MODE_FLAG_CSYNC);
+ /// Composite sync is active high.
+ pub const PCSYNC: Self = Self(bindings::DRM_MODE_FLAG_PCSYNC);
+ /// Composite sync is active low.
+ pub const NCSYNC: Self = Self(bindings::DRM_MODE_FLAG_NCSYNC);
+ /// The mode carries a horizontal skew value.
+ pub const HSKEW: Self = Self(bindings::DRM_MODE_FLAG_HSKEW);
+ /// The mode is double-clocked.
+ pub const DBLCLK: Self = Self(bindings::DRM_MODE_FLAG_DBLCLK);
+ /// The mode uses a half-rate clock.
+ pub const CLKDIV2: Self = Self(bindings::DRM_MODE_FLAG_CLKDIV2);
+
+ /// Return whether all flags in `other` are set.
+ pub fn contains(self, other: Self) -> bool {
+ self & other == other
+ }
+}
+
+impl core::ops::BitOr for ModeFlags {
+ type Output = Self;
+
+ fn bitor(self, rhs: Self) -> Self::Output {
+ Self(self.0 | rhs.0)
+ }
+}
+
+impl core::ops::BitAnd for ModeFlags {
+ type Output = Self;
+
+ fn bitand(self, rhs: Self) -> Self::Output {
+ Self(self.0 & rhs.0)
+ }
+}
+
/// The essential timing fields of a display mode.
#[derive(Clone, Copy)]
pub struct ModeTimings {
@@ -32,6 +86,8 @@ pub struct ModeTimings {
pub vsync_end: u16,
/// Total vertical lines including blanking.
pub vtotal: u16,
+ /// Signal polarity and scan-format flags.
+ pub flags: ModeFlags,
}
/// DRM kernel-internal display mode structure.
@@ -84,6 +140,7 @@ pub fn from_timings(t: ModeTimings) -> Result<Self> {
mode.vsync_start = t.vsync_start;
mode.vsync_end = t.vsync_end;
mode.vtotal = t.vtotal;
+ mode.flags = t.flags.0;
Ok(Self {
inner: Opaque::new(mode),
@@ -202,10 +259,26 @@ pub fn clock(&self) -> i32 {
unsafe { (*self.as_raw()).clock }
}
+ /// Return the mode's signal-polarity and scan-format flags.
+ #[inline]
+ pub fn flags(&self) -> ModeFlags {
+ // SAFETY: Reading this field is safe via the type invariants.
+ ModeFlags(unsafe { (*self.as_raw()).flags })
+ }
+
/// Return the refresh rate in Hz as computed by DRM.
#[inline]
pub fn vrefresh(&self) -> i32 {
// SAFETY: `drm_mode_vrefresh` only reads this valid display mode.
unsafe { bindings::drm_mode_vrefresh(self.as_raw()) }
}
+
+ /// Return the CTA-861 Video Identification Code matching this mode.
+ ///
+ /// A return value of zero means the mode is not one of the CTA-861 modes known to DRM.
+ #[inline]
+ pub fn cea_vic(&self) -> u8 {
+ // SAFETY: `drm_match_cea_mode` only reads this valid display mode.
+ unsafe { bindings::drm_match_cea_mode(self.as_raw()) }
+ }
}
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 19/23] rust: drm: expose CRTC mode changes
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (17 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 18/23] rust: drm: expose mode flags and CTA VIC matching Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 20/23] rust: drm: kms: add synthesized CVT connector modes Mike Lothian
` (3 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Allow Rust DRM drivers to distinguish a modeset or enable transition
from an ordinary atomic page flip. This avoids repeating mode-specific
validation on the page-flip hot path.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/crtc.rs | 139 +++++++++++++++++++++++++++++++++++-
1 file changed, 138 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 892f04f04e22..9e888c4e2f68 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -31,6 +31,17 @@
pub struct ColorLut(bindings::drm_color_lut);
impl ColorLut {
+ /// Build an entry. Mainly useful for tests and for drivers synthesising a ramp.
+ #[inline]
+ pub const fn new(red: u16, green: u16, blue: u16) -> Self {
+ Self(bindings::drm_color_lut {
+ red,
+ green,
+ blue,
+ reserved: 0,
+ })
+ }
+
/// Red channel value.
pub fn red(&self) -> u16 {
self.0.red
@@ -47,6 +58,65 @@ pub fn blue(&self) -> u16 {
}
}
+/// A colour transformation matrix, as programmed through the CRTC's `CTM` property.
+///
+/// The matrix is applied to the pixel values that the degamma LUT produced, before the gamma LUT:
+///
+/// ```text
+/// out matrix in
+/// |R| |0 1 2| |R|
+/// |G| = |3 4 5| x |G|
+/// |B| |6 7 8| |B|
+/// ```
+#[repr(transparent)]
+pub struct ColorCtm(bindings::drm_color_ctm);
+
+impl ColorCtm {
+ /// Build a matrix from raw S31.32 **sign-magnitude** entries. Mainly useful for tests.
+ #[inline]
+ pub const fn from_raw(matrix: [u64; 9]) -> Self {
+ Self(bindings::drm_color_ctm { matrix })
+ }
+
+ /// The raw matrix, in the UAPI's S31.32 **sign-magnitude** encoding.
+ ///
+ /// Prefer [`Self::coefficient`], which decodes an entry into an ordinary signed value.
+ #[inline]
+ pub fn raw(&self) -> &[u64; 9] {
+ &self.0.matrix
+ }
+
+ /// Return matrix entry `i` as a two's-complement S31.32 fixed-point value, or [`None`] if `i`
+ /// is out of range.
+ ///
+ /// The UAPI encodes these in **sign-magnitude, not two's complement** (bit 63 is the sign and
+ /// the remaining 63 bits are the magnitude), so reading the `u64` as an `i64` silently turns
+ /// every negative coefficient into a huge positive one. Decoding here means no driver has to
+ /// remember that.
+ #[inline]
+ pub fn coefficient(&self, i: usize) -> Option<i64> {
+ let raw = *self.0.matrix.get(i)?;
+ // The magnitude is capped so it always fits a positive i64.
+ let magnitude = (raw & !(1u64 << 63)) as i64;
+ Some(if raw & (1u64 << 63) != 0 {
+ -magnitude
+ } else {
+ magnitude
+ })
+ }
+
+ /// Return all nine coefficients decoded by [`Self::coefficient`].
+ #[inline]
+ pub fn coefficients(&self) -> [i64; 9] {
+ let mut out = [0i64; 9];
+ for (i, o) in out.iter_mut().enumerate() {
+ // The index is in range by construction, so the fallback is unreachable.
+ *o = self.coefficient(i).unwrap_or(0);
+ }
+ out
+ }
+}
+
/// The main trait for implementing the [`struct drm_crtc`] API for [`Crtc`].
///
/// Any KMS driver should have at least one implementation of this type, which allows them to create
@@ -440,8 +510,28 @@ pub fn new<'a, PrimaryData, CursorData>(
/// Call this during [`KmsDriver::probe`](crate::drm::kms::KmsDriver::probe), before the device
/// is registered.
pub fn enable_gamma(&self, gamma_size: u32) {
+ self.enable_color_mgmt(0, false, gamma_size)
+ }
+
+ /// Enable colour management on this CRTC, creating the `DEGAMMA_LUT`, `CTM` and `GAMMA_LUT`
+ /// properties that userspace can program.
+ ///
+ /// A size of zero suppresses the corresponding LUT property, and `has_ctm` selects whether the
+ /// `CTM` property is created. The programmed values are then readable from the CRTC state via
+ /// [`RawCrtcState::degamma_lut`], [`RawCrtcState::ctm`] and [`RawCrtcState::gamma_lut`].
+ ///
+ /// A driver with no colour hardware can still advertise these and apply them in software while
+ /// it has the pixels; compositors that colour-correct through the CRTC properties (rather than
+ /// by rewriting the framebuffer) otherwise have nowhere to put the correction on such an
+ /// output.
+ ///
+ /// Call this during [`KmsDriver::probe`](crate::drm::kms::KmsDriver::probe), before the device
+ /// is registered.
+ pub fn enable_color_mgmt(&self, degamma_size: u32, has_ctm: bool, gamma_size: u32) {
// SAFETY: `as_raw()` is a valid, not-yet-registered CRTC.
- unsafe { bindings::drm_crtc_enable_color_mgmt(self.as_raw(), 0, false, gamma_size) };
+ unsafe {
+ bindings::drm_crtc_enable_color_mgmt(self.as_raw(), degamma_size, has_ctm, gamma_size)
+ };
}
}
@@ -766,6 +856,12 @@ fn active(&self) -> bool {
unsafe { (*self.as_raw()).active }
}
+ /// Returns whether the mode or enable state changed in this atomic state.
+ fn mode_changed(&self) -> bool {
+ // SAFETY: The atomic-state API serializes access to this state, including its bitfields.
+ unsafe { (*self.as_raw()).mode_changed() }
+ }
+
/// Return the display mode programmed into this CRTC state.
fn mode(&self) -> &DisplayMode {
// SAFETY: `mode` is embedded in the CRTC state and therefore has the same lifetime. The
@@ -793,6 +889,47 @@ fn gamma_lut(&self) -> Option<&[ColorLut]> {
// entries valid for the state's lifetime.
Some(unsafe { core::slice::from_raw_parts(data.cast::<ColorLut>(), n) })
}
+
+ /// Returns the CRTC's degamma LUT for this state as an array of [`ColorLut`] entries, or
+ /// [`None`] if none is programmed. Requires a non-zero `degamma_size` to have been passed to
+ /// [`UnregisteredCrtc::enable_color_mgmt`].
+ fn degamma_lut(&self) -> Option<&[ColorLut]> {
+ // SAFETY: `as_raw()` is a valid `drm_crtc_state`.
+ let blob = unsafe { (*self.as_raw()).degamma_lut };
+ if blob.is_null() {
+ return None;
+ }
+ // SAFETY: a non-null degamma_lut blob is valid for the state's lifetime.
+ let (data, length) = unsafe { ((*blob).data, (*blob).length) };
+ let n = length / core::mem::size_of::<ColorLut>();
+ if data.is_null() || n == 0 {
+ return None;
+ }
+ // SAFETY: `ColorLut` is transparent over `drm_color_lut`; the blob holds `n` contiguous
+ // entries valid for the state's lifetime.
+ Some(unsafe { core::slice::from_raw_parts(data.cast::<ColorLut>(), n) })
+ }
+
+ /// Returns the CRTC's colour transformation matrix for this state, or [`None`] if none is
+ /// programmed. Requires `has_ctm` to have been passed to
+ /// [`UnregisteredCrtc::enable_color_mgmt`].
+ fn ctm(&self) -> Option<&ColorCtm> {
+ // SAFETY: `as_raw()` is a valid `drm_crtc_state`.
+ let blob = unsafe { (*self.as_raw()).ctm };
+ if blob.is_null() {
+ return None;
+ }
+ // SAFETY: a non-null ctm blob is valid for the state's lifetime.
+ let (data, length) = unsafe { ((*blob).data, (*blob).length) };
+ // DRM validates the blob length when the property is set, but this is the boundary where
+ // a short blob would become an out-of-bounds read of nine u64s.
+ if data.is_null() || length < core::mem::size_of::<ColorCtm>() {
+ return None;
+ }
+ // SAFETY: `ColorCtm` is transparent over `drm_color_ctm`, and the blob is at least that
+ // long and valid for the state's lifetime.
+ Some(unsafe { &*data.cast::<ColorCtm>() })
+ }
}
impl<T: AsRawCrtcState> RawCrtcState for T {}
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 20/23] rust: drm: kms: add synthesized CVT connector modes
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (18 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 19/23] rust: drm: expose CRTC mode changes Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 21/23] rust: drm: kms: read a connector's colorimetry and HDR metadata Mike Lothian
` (2 subsequent siblings)
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
Expose a lock-scoped helper for adding a driver-synthesized CVT timing
to a connector probe result. This lets virtual and transport-backed
displays offer valid continuous-frequency modes without reaching into
DRM mode lists.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/connector.rs | 84 ++++++++++++++++++++++++++++++++
1 file changed, 84 insertions(+)
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index dd126469788f..952c8e02777b 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -495,6 +495,60 @@ pub fn attach_encoder<E>(&self, encoder: &UnregisteredEncoder<E>) -> Result
bindings::drm_connector_attach_encoder(self.as_raw(), encoder.as_raw())
})
}
+
+ /// Attach the HDR output metadata property to this [`Connector`].
+ ///
+ /// This property carries a blob supplied by userspace. Drivers must still validate and apply
+ /// the metadata in their atomic commit path before claiming that HDR output is supported.
+ pub fn attach_hdr_output_metadata_property(&self) {
+ // SAFETY: `self` is an initialized connector owned by this DRM device. The helper only
+ // attaches the mode-config-owned standard property to its mode object.
+ unsafe {
+ bindings::drm_connector_attach_hdr_output_metadata_property(self.as_raw());
+ }
+ }
+
+ /// Create and attach the standard DP colorspace property to this [`Connector`].
+ ///
+ /// A zero mask asks DRM to expose every colorspace defined for DisplayPort. A driver must
+ /// still reject values its sink or transport cannot actually carry in its atomic check.
+ pub fn attach_colorspace_property(&self) -> Result {
+ to_result(unsafe { bindings::drm_mode_create_dp_colorspace_property(self.as_raw(), 0) })?;
+ // SAFETY: the successful create call above initialized `colorspace_property` for this
+ // connector; the C helper only attaches that property to this connector's mode object.
+ to_result(unsafe { bindings::drm_connector_attach_colorspace_property(self.as_raw()) })
+ }
+
+ /// Attach the standard `max bpc` range property to this [`Connector`].
+ ///
+ /// `min_bpc` and `max_bpc` are validated before conversion so callers cannot wrap an invalid
+ /// range through the C `int` API. DRM requires the connector to have an atomic state before
+ /// this helper is called; newly-created Rust connectors acquire that state here.
+ pub fn attach_max_bpc_property(&self, min_bpc: u32, max_bpc: u32) -> Result {
+ if min_bpc == 0 || min_bpc > max_bpc || max_bpc > i32::MAX as u32 {
+ return Err(EINVAL);
+ }
+
+ // `drm_connector_attach_max_bpc_property()` writes the initial bpc values into the
+ // connector state. `KmsDriver::create_objects()` runs before the mode-config-wide reset,
+ // so initialize our state through the driver's Rust reset callback when necessary.
+ let state = unsafe { (*self.as_raw()).state };
+ if state.is_null() {
+ // SAFETY: `self` is a newly initialized `Connector<T>` and this unregistered typestate
+ // prevents concurrent access. The callback creates the matching `ConnectorState<T>`.
+ unsafe { connector_reset_callback::<T::State>(self.as_raw()) };
+ }
+
+ // SAFETY: `self` is initialized and now owns a connector state. The validated bounds fit
+ // the C API's signed integer parameters, and the helper only installs a DRM core property.
+ to_result(unsafe {
+ bindings::drm_connector_attach_max_bpc_property(
+ self.as_raw(),
+ min_bpc as i32,
+ max_bpc as i32,
+ )
+ })
+ }
}
/// Common methods available on any type which implements [`AsRawConnector`].
@@ -723,6 +777,36 @@ pub fn set_preferred_mode(&self, (h_pref, w_pref): (u32, u32)) {
unsafe { bindings::drm_set_preferred_mode(self.as_raw(), h_pref, w_pref) }
}
+ /// Add a driver-synthesised CVT mode to this connector's probed mode list.
+ ///
+ /// For a display whose EDID declares continuous frequencies, a driver may legitimately offer a
+ /// timing the EDID does not itself enumerate. `reduced` selects CVT reduced blanking (CVT-RB),
+ /// which matters when the *pixel clock* rather than the pixel rate is the constrained
+ /// resource -- RB cuts the clock for the same active pixels.
+ ///
+ /// Returns `EINVAL` if the core could not build the timing.
+ pub fn add_cvt_mode(
+ &self,
+ hdisplay: i32,
+ vdisplay: i32,
+ vrefresh: i32,
+ reduced: bool,
+ ) -> Result {
+ let dev = self.drm_dev().as_raw();
+ // SAFETY: `dev` is this connector's live `drm_device`; `drm_cvt_mode` only computes a
+ // timing and allocates it, and we hold the mode-config lock via our type invariants.
+ let mode = unsafe {
+ bindings::drm_cvt_mode(dev, hdisplay, vdisplay, vrefresh, reduced, false, false)
+ };
+ if mode.is_null() {
+ return Err(EINVAL);
+ }
+ // SAFETY: `mode` was just allocated by `drm_cvt_mode` and ownership passes to the
+ // connector here; we hold the locks required to modify its mode list.
+ unsafe { bindings::drm_mode_probed_add(self.as_raw(), mode) };
+ Ok(())
+ }
+
/// Parse an EDID, update the connector information, and add its advertised modes.
///
/// Returns the number of modes added.
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 21/23] rust: drm: kms: read a connector's colorimetry and HDR metadata
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (19 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 20/23] rust: drm: kms: add synthesized CVT connector modes Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 22/23] rust: drm: kms: walk the CRTCs an atomic commit carries Mike Lothian
2026-08-26 16:31 ` [PATCH v3 23/23] rust: drm: kms: expose a connector's requested link depth Mike Lothian
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
A driver that carries a transfer function to its sink needs the connector
state's colorimetry and HDR_OUTPUT_METADATA, and needs to reach the
connector state routed to a CRTC from the CRTC's own atomic callback.
Add ConnectorState::hdr_output_eotf() and
AtomicState::new_connector_state_for_crtc().
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/atomic.rs | 104 +++++++++++++++++++++++++++++++
rust/kernel/drm/kms/connector.rs | 77 +++++++++++++++++++++++
rust/kernel/drm/kms/crtc.rs | 13 ++++
3 files changed, 194 insertions(+)
diff --git a/rust/kernel/drm/kms/atomic.rs b/rust/kernel/drm/kms/atomic.rs
index 18dc136940f3..f9f91edc89c3 100644
--- a/rust/kernel/drm/kms/atomic.rs
+++ b/rust/kernel/drm/kms/atomic.rs
@@ -96,6 +96,88 @@ pub fn get_old_connector_state<C>(&self, connector: &C) -> Option<&C::State>
.map(|p| C::State::from_raw(p))
}
}
+
+ /// Return the new state of the first connector routed to `crtc` in this [`AtomicState`], if
+ /// any.
+ ///
+ /// This is the Rust spelling of walking `for_each_new_connector_in_state()` looking for
+ /// `conn_state->crtc == crtc`, which is how a CRTC callback reaches the connector properties
+ /// that describe the signal it is about to drive -- colorimetry, HDR metadata, `max bpc`.
+ /// Those live on the connector state, but the driver decisions they feed are frequently made
+ /// where only the CRTC is in hand.
+ ///
+ /// The state is returned opaquely because the caller is looking across mode objects and has
+ /// no way to name the connector's driver-private state type. A CRTC that clones to several
+ /// connectors gets the first; a driver that cares about the difference should walk the
+ /// connectors itself.
+ pub fn new_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnectorState<T>>
+ where
+ C: ModesettableCrtc + ModeObject<Driver = T>,
+ {
+ let crtc_raw = crtc.as_raw();
+ // SAFETY: `state` is initialized via our type invariants, and `connectors` /
+ // `num_connector` are invariant for as long as we hold a reference to it.
+ let (connectors, num) = unsafe {
+ let raw = self.as_raw();
+ ((*raw).connectors, (*raw).num_connector)
+ };
+ if connectors.is_null() || num <= 0 {
+ return None;
+ }
+ for i in 0..num as usize {
+ // SAFETY: `connectors` points to `num_connector` initialized entries.
+ let new_state = unsafe { (*connectors.add(i)).new_state };
+ if new_state.is_null() {
+ continue;
+ }
+ // SAFETY: a non-null `new_state` is a valid `drm_connector_state` for the lifetime of
+ // the atomic state.
+ if unsafe { (*new_state).crtc } != crtc_raw {
+ continue;
+ }
+ // SAFETY: as above, and the returned reference borrows from `self`, so it cannot
+ // outlive the atomic state that owns the connector state.
+ return Some(unsafe { OpaqueConnectorState::<T>::from_raw(new_state) });
+ }
+ None
+ }
+
+ /// Return the old state of the first connector routed to `crtc` in this [`AtomicState`], if
+ /// any.
+ ///
+ /// The counterpart to [`Self::new_connector_state_for_crtc`], for a driver comparing the two
+ /// to decide whether a connector property it consumes has changed.
+ pub fn old_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnectorState<T>>
+ where
+ C: ModesettableCrtc + ModeObject<Driver = T>,
+ {
+ let crtc_raw = crtc.as_raw();
+ // SAFETY: `state` is initialized via our type invariants, and `connectors` /
+ // `num_connector` are invariant for as long as we hold a reference to it.
+ let (connectors, num) = unsafe {
+ let raw = self.as_raw();
+ ((*raw).connectors, (*raw).num_connector)
+ };
+ if connectors.is_null() || num <= 0 {
+ return None;
+ }
+ for i in 0..num as usize {
+ // SAFETY: `connectors` points to `num_connector` initialized entries.
+ let old_state = unsafe { (*connectors.add(i)).old_state };
+ if old_state.is_null() {
+ continue;
+ }
+ // SAFETY: a non-null `old_state` is a valid `drm_connector_state` for the lifetime of
+ // the atomic state.
+ if unsafe { (*old_state).crtc } != crtc_raw {
+ continue;
+ }
+ // SAFETY: as above, and the returned reference borrows from `self`, so it cannot
+ // outlive the atomic state that owns the connector state.
+ return Some(unsafe { OpaqueConnectorState::<T>::from_raw(old_state) });
+ }
+ None
+ }
}
// SAFETY: DRM atomic state objects are always reference counted and the get/put functions satisfy
@@ -188,6 +270,28 @@ pub fn get_old_connector_state<C>(&self, connector: &C) -> Option<&C::State>
self.state.get_old_connector_state(connector)
}
+ /// Return the new state of the first connector routed to `crtc`, if any.
+ ///
+ /// See [`AtomicState::new_connector_state_for_crtc`]. This borrows the connector state rather
+ /// than taking a mutator out for it, so it does not participate in the mutator bookkeeping and
+ /// cannot conflict with [`Self::get_new_connector_state`].
+ pub fn new_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnectorState<T>>
+ where
+ C: ModesettableCrtc + ModeObject<Driver = T>,
+ {
+ self.state.new_connector_state_for_crtc(crtc)
+ }
+
+ /// Return the old state of the first connector routed to `crtc`, if any.
+ ///
+ /// See [`AtomicState::old_connector_state_for_crtc`].
+ pub fn old_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnectorState<T>>
+ where
+ C: ModesettableCrtc + ModeObject<Driver = T>,
+ {
+ self.state.old_connector_state_for_crtc(crtc)
+ }
+
/// Retrieve the last committed atomic state for `plane` if `plane` has already been added to
/// the atomic state being composed.
///
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index 952c8e02777b..231857cc1f20 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -922,7 +922,84 @@ fn connector(&self) -> &Self::Connector {
// `self.state.connector` points to a valid instance of a `Connector<T>`
unsafe { Self::Connector::from_raw((*self.as_raw()).connector) }
}
+
+ /// The colorimetry userspace has requested through the `Colorspace` property, as a
+ /// [`enum drm_colorspace`] value.
+ ///
+ /// Meaningful only on a connector that
+ /// [`UnregisteredConnector::attach_colorspace_property`] was called for; everything else
+ /// leaves it at `DRM_MODE_COLORIMETRY_DEFAULT`.
+ ///
+ /// [`enum drm_colorspace`]: srctree/include/drm/drm_connector.h
+ fn colorspace(&self) -> u32 {
+ self.as_raw().colorspace
+ }
+
+ /// The electro-optical transfer function from the `HDR_OUTPUT_METADATA` blob, or [`None`] if
+ /// userspace has not set one.
+ ///
+ /// This is deliberately just the curve: the rest of the infoframe is mastering-display
+ /// metadata for the sink, and a driver that only needs to know *which curve the pixels are
+ /// encoded in* should not have to reason about the union's other members or their versioning.
+ ///
+ /// [`struct hdr_output_metadata`]: srctree/include/uapi/drm/drm_mode.h
+ fn hdr_output_eotf(&self) -> Option<Eotf> {
+ let blob = self.as_raw().hdr_output_metadata;
+ if blob.is_null() {
+ return None;
+ }
+ // SAFETY: a non-null `hdr_output_metadata` blob is valid for the state's lifetime.
+ let (data, length) = unsafe { ((*blob).data, (*blob).length) };
+ // DRM validates the blob length when the property is set, but this is the boundary where
+ // a short blob would become an out-of-bounds read.
+ if data.is_null() || length < core::mem::size_of::<bindings::hdr_output_metadata>() {
+ return None;
+ }
+ // SAFETY: the blob is at least a whole `hdr_output_metadata` and lives as long as the
+ // state. `eotf` is the first byte of the only union member DRM defines.
+ let eotf = unsafe {
+ (*data.cast::<bindings::hdr_output_metadata>())
+ .__bindgen_anon_1
+ .hdmi_metadata_type1
+ .eotf
+ };
+ Some(Eotf::from_raw(eotf))
+ }
+}
+/// An electro-optical transfer function named by a `HDR_OUTPUT_METADATA` blob.
+///
+/// Mirrors the `HDMI_EOTF_*` values in [`enum hdmi_eotf`]. A driver matches on this rather than
+/// comparing against the raw constants, so the one place that has to agree with the C enum is
+/// [`Eotf::from_raw`].
+///
+/// [`enum hdmi_eotf`]: srctree/include/linux/hdmi.h
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Eotf {
+ /// Ordinary SDR gamma.
+ TraditionalGammaSdr,
+ /// The traditional HDR gamma curve.
+ TraditionalGammaHdr,
+ /// SMPTE ST 2084, i.e. PQ. What a compositor sets to drive an output in HDR10.
+ SmpteSt2084,
+ /// BT.2100 hybrid log-gamma.
+ Bt2100Hlg,
+ /// A value this kernel does not name, carried through rather than discarded.
+ Other(u8),
}
+
+impl Eotf {
+ /// Classify the raw `eotf` byte from an infoframe.
+ fn from_raw(eotf: u8) -> Self {
+ match u32::from(eotf) {
+ bindings::hdmi_eotf_HDMI_EOTF_TRADITIONAL_GAMMA_SDR => Self::TraditionalGammaSdr,
+ bindings::hdmi_eotf_HDMI_EOTF_TRADITIONAL_GAMMA_HDR => Self::TraditionalGammaHdr,
+ bindings::hdmi_eotf_HDMI_EOTF_SMPTE_ST2084 => Self::SmpteSt2084,
+ bindings::hdmi_eotf_HDMI_EOTF_BT_2100_HLG => Self::Bt2100Hlg,
+ _ => Self::Other(eotf),
+ }
+ }
+}
+
impl<T: AsRawConnectorState> RawConnectorState for T {}
/// The main interface for a [`struct drm_connector_state`].
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 9e888c4e2f68..ec01ae0430f7 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -1047,6 +1047,19 @@ pub(super) fn new<D: KmsDriver>(
}
}
+impl<'a, T: FromRawCrtcState> CrtcStateMutator<'a, T> {
+ /// Require a full mode set for this CRTC.
+ ///
+ /// Called from [`DriverCrtc::atomic_check`] when something the core does not track has changed
+ /// in a way the hardware can only adopt by being reprogrammed, such as a connector property
+ /// that forms part of the signal description the driver sends to its device.
+ pub fn set_mode_changed(&mut self, changed: bool) {
+ // SAFETY: `as_raw()` is a valid `drm_crtc_state`, and holding this mutator is proof that
+ // no other reference to it exists.
+ unsafe { (*self.as_raw()).set_mode_changed(changed) };
+ }
+}
+
impl<'a, T: DriverCrtcState> CrtcStateMutator<'a, CrtcState<T>> {
super::impl_from_opaque_mode_obj! {
fn <D, C>(CrtcStateMutator<'a, OpaqueCrtcState<D>>) -> Self
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 22/23] rust: drm: kms: walk the CRTCs an atomic commit carries
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (20 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 21/23] rust: drm: kms: read a connector's colorimetry and HDR metadata Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
2026-08-26 16:31 ` [PATCH v3 23/23] rust: drm: kms: expose a connector's requested link depth Mike Lothian
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, David Airlie, Simona Vetter, Danilo Krummrich,
Alice Ryhl, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
A driver enforcing a constraint its CRTCs share -- a bandwidth budget,
a clock source, a fixed pool of scanout engines -- has to weigh what
every head will be once the commit lands, and a per-CRTC callback can
only reach its own new state. Reaching the others through committed
state answers a different question: it prices each sibling at what it
is leaving rather than what it is taking, so two heads that both rise
in one commit each find the other still low, pass individually, and
break the shared limit together.
Add the walk over the CRTCs an atomic state carries, the Rust spelling
of for_each_new_crtc_in_state(), on both the state and its mutator.
The CRTC is handed over alongside its new state because the
driver-private data that names what a CRTC drives hangs off the CRTC,
not off the state.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/kms/atomic.rs | 52 +++++++++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/rust/kernel/drm/kms/atomic.rs b/rust/kernel/drm/kms/atomic.rs
index f9f91edc89c3..24daeaeca075 100644
--- a/rust/kernel/drm/kms/atomic.rs
+++ b/rust/kernel/drm/kms/atomic.rs
@@ -142,6 +142,48 @@ pub fn new_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnect
None
}
+ /// Invoke `f` for every CRTC this [`AtomicState`] carries a new state for, passing the CRTC
+ /// and that state.
+ ///
+ /// This is the Rust spelling of walking `for_each_new_crtc_in_state()`.
+ ///
+ /// A driver enforcing a constraint its heads share -- a bandwidth budget, a clock source, a
+ /// fixed pool of scanout engines -- has to weigh what every head will be once the commit
+ /// lands. A per-CRTC callback that consults committed state instead sees each sibling at its
+ /// old value, so two heads that both rise in one commit each find the other still low, pass
+ /// individually, and break the shared limit together.
+ pub fn for_each_new_crtc_state<F>(&self, mut f: F)
+ where
+ F: FnMut(&Crtc<T::Crtc>, &OpaqueCrtcState<T>),
+ {
+ // SAFETY: `state` is initialized via our type invariants, and `crtcs` together with the
+ // device's `num_crtc` are invariant for as long as we hold a reference to it.
+ let (crtcs, num) = unsafe {
+ let raw = self.as_raw();
+ ((*raw).crtcs, (*(*raw).dev).mode_config.num_crtc)
+ };
+ if crtcs.is_null() || num <= 0 {
+ return;
+ }
+ for i in 0..num as usize {
+ // SAFETY: `crtcs` points to `num_crtc` initialized entries.
+ let (ptr, new_state) = unsafe { ((*crtcs.add(i)).ptr, (*crtcs.add(i)).new_state) };
+ if ptr.is_null() || new_state.is_null() {
+ continue;
+ }
+ // SAFETY: every CRTC of a `KmsDriver` device is a `Crtc<T::Crtc>`, and a non-null
+ // `new_state` is a valid `drm_crtc_state`. Both borrow from `self`, so neither can
+ // outlive the atomic state owning them.
+ let (crtc, state) = unsafe {
+ (
+ Crtc::<T::Crtc>::from_raw(ptr),
+ OpaqueCrtcState::<T>::from_raw(new_state),
+ )
+ };
+ f(crtc, state);
+ }
+ }
+
/// Return the old state of the first connector routed to `crtc` in this [`AtomicState`], if
/// any.
///
@@ -282,6 +324,16 @@ pub fn new_connector_state_for_crtc<C>(&self, crtc: &C) -> Option<&OpaqueConnect
self.state.new_connector_state_for_crtc(crtc)
}
+ /// Invoke `f` for every CRTC this state carries a new state for.
+ ///
+ /// See [`AtomicState::for_each_new_crtc_state`].
+ pub fn for_each_new_crtc_state<F>(&self, f: F)
+ where
+ F: FnMut(&Crtc<T::Crtc>, &OpaqueCrtcState<T>),
+ {
+ self.state.for_each_new_crtc_state(f)
+ }
+
/// Return the old state of the first connector routed to `crtc`, if any.
///
/// See [`AtomicState::old_connector_state_for_crtc`].
^ permalink raw reply related [flat|nested] 24+ messages in thread* [PATCH v3 23/23] rust: drm: kms: expose a connector's requested link depth
2026-08-26 16:31 [PATCH v3 0/23] rust: drm: KMS abstractions for a Rust display driver Mike Lothian
` (21 preceding siblings ...)
2026-08-26 16:31 ` [PATCH v3 22/23] rust: drm: kms: walk the CRTCs an atomic commit carries Mike Lothian
@ 2026-08-26 16:31 ` Mike Lothian
22 siblings, 0 replies; 24+ messages in thread
From: Mike Lothian @ 2026-08-26 16:31 UTC (permalink / raw)
To: dri-devel
Cc: Mike Lothian, Danilo Krummrich, Alice Ryhl, David Airlie,
Simona Vetter, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, rust-for-linux, linux-kernel
`max bpc` is how userspace asks for the number of bits the link
carries, and it is deliberately independent of the framebuffer's
format: scanning out an eight-bit surface over a ten-bit link is the
ordinary case. A driver could attach the property but had no way to
read back what was asked for, so the request could only be ignored.
Add the accessor, and make the linear format modifier nameable outside
the crate so a driver that accepts only linear scanout can say so in
its plane's modifier list rather than leaving userspace to infer it.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
---
rust/kernel/drm/fourcc.rs | 5 ++++-
rust/kernel/drm/kms/connector.rs | 16 ++++++++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/drm/fourcc.rs b/rust/kernel/drm/fourcc.rs
index 010823c4c86c..3a68af66f236 100644
--- a/rust/kernel/drm/fourcc.rs
+++ b/rust/kernel/drm/fourcc.rs
@@ -13,7 +13,10 @@ const fn fourcc_code(a: u8, b: u8, c: u8, d: u8) -> u32 {
// function-like macros in bindgen yet.
pub(crate) const FORMAT_MOD_INVALID: u64 = 0xffffffffffffff;
/// Linear framebuffer layout (`DRM_FORMAT_MOD_LINEAR`).
-pub(crate) const FORMAT_MOD_LINEAR: u64 = 0;
+///
+/// A driver that accepts only linear scanout has to say so through the plane's format-modifier
+/// list, or userspace sees no `IN_FORMATS` property and has to guess what the plane will take.
+pub const FORMAT_MOD_LINEAR: u64 = 0;
/// 32 bpp RGB with unused alpha.
pub const XRGB8888: u32 = fourcc_code(b'X', b'R', b'2', b'4');
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index 231857cc1f20..633f4f76a610 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -935,6 +935,22 @@ fn colorspace(&self) -> u32 {
self.as_raw().colorspace
}
+ /// The bits per colour channel userspace has asked the link to carry, through the `max bpc`
+ /// property.
+ ///
+ /// This is a property of the *link*, not of the framebuffer: userspace routinely scans out an
+ /// eight-bit surface over a ten-bit link, and a driver that derives its output depth from the
+ /// framebuffer format alone silently ignores what was asked for.
+ ///
+ /// Meaningful only on a connector that
+ /// [`UnregisteredConnector::attach_max_bpc_property`] was called for; everything else leaves
+ /// it at zero.
+ fn max_requested_bpc(&self) -> u32 {
+ // `max_requested_bpc` is an `unsigned int` clamped by DRM to the range the driver gave
+ // `drm_connector_attach_max_bpc_property()`, so it needs no validation here.
+ self.as_raw().max_requested_bpc as u32
+ }
+
/// The electro-optical transfer function from the `HDR_OUTPUT_METADATA` blob, or [`None`] if
/// userspace has not set one.
///
^ permalink raw reply related [flat|nested] 24+ messages in thread