[PATCH v2 1/1] rust: drm: add RENDER_CAPABILITY flag for render node support

[Laura Nao <laura.nao@collabora.com>]

Add RENDER_CAPABILITY bool constant to the Driver trait to control
render node support. When enabled, the driver exposes /dev/dri/renderDXX
render nodes to userspace. The flag defaults to false, drivers can opt
in by setting it to true in their Driver implementation.

This is then enabled in the Tyr driver, while it's left disabled for
Nova for the time being.

Co-developed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Laura Nao <laura.nao@collabora.com>
---
 drivers/gpu/drm/tyr/driver.rs |  1 +
 rust/kernel/drm/device.rs     | 12 +++++++++++-
 rust/kernel/drm/driver.rs     |  5 +++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
index e20a5978eed6..b7ae37ce3a1b 100644
--- a/drivers/gpu/drm/tyr/driver.rs
+++ b/drivers/gpu/drm/tyr/driver.rs
@@ -186,6 +186,7 @@ impl drm::Driver for TyrDrmDriver {
     type Object = drm::gem::shmem::Object<BoData>;
 
     const INFO: drm::DriverInfo = INFO;
+    const RENDER_CAPABILITY: bool = true;
 
     kernel::declare_drm_ioctls! {
         (PANTHOR_DEV_QUERY, drm_panthor_dev_query, ioctl::RENDER_ALLOW, TyrDrmFileData::dev_query),
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index adbafe8db54d..e121303d88f0 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -80,6 +80,16 @@ pub struct Device<T: drm::Driver> {
 }
 
 impl<T: drm::Driver> Device<T> {
+    const fn compute_features() -> u32 {
+        let mut features = drm::driver::FEAT_GEM;
+
+        if T::RENDER_CAPABILITY {
+            features |= drm::driver::FEAT_RENDER;
+        }
+
+        features
+    }
+
     const VTABLE: bindings::drm_driver = drm_legacy_fields! {
         load: None,
         open: Some(drm::File::<T::File>::open_callback),
@@ -105,7 +115,7 @@ impl<T: drm::Driver> Device<T> {
         name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
         desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),
 
-        driver_features: drm::driver::FEAT_GEM,
+        driver_features: Self::compute_features(),
         ioctls: T::IOCTLS.as_ptr(),
         num_ioctls: T::IOCTLS.len() as i32,
         fops: &Self::GEM_FOPS,
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 5233bdebc9fc..92cbc26ce11f 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -16,6 +16,8 @@
 
 /// Driver use the GEM memory manager. This should be set for all modern drivers.
 pub(crate) const FEAT_GEM: u32 = bindings::drm_driver_feature_DRIVER_GEM;
+/// Driver supports render nodes, i.e.: /dev/dri/renderDXX devices.
+pub(crate) const FEAT_RENDER: u32 = bindings::drm_driver_feature_DRIVER_RENDER;
 
 /// Information data for a DRM Driver.
 pub struct DriverInfo {
@@ -115,6 +117,9 @@ pub trait Driver {
 
     /// IOCTL list. See `kernel::drm::ioctl::declare_drm_ioctls!{}`.
     const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor];
+
+    /// Sets the `DRIVER_RENDER` feature for this driver.
+    const RENDER_CAPABILITY: bool = false;
 }
 
 /// The registration type of a `drm::Device`.
-- 
2.39.5