[PATCH 4/7] drm/rust: allow drivers to override file operations

[Deborah Brouwer <deborah.brouwer@collabora.com>]

Add a Driver::FOPS associated constant so Rust DRM drivers can override
or extend the default file operations table.

Use the driver's FOPS in drm::Device instead of always constructing the
default GEM file operations internally.

Also make drm::gem::create_fops() public so drivers can build on top of
the default GEM handlers while overriding selected operations such as
mmap.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
---
 rust/kernel/drm/device.rs  | 4 ++--
 rust/kernel/drm/driver.rs  | 6 ++++++
 rust/kernel/drm/gem/mod.rs | 3 ++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index adbafe8db54d..82760a9a426e 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -108,10 +108,10 @@ impl<T: drm::Driver> Device<T> {
         driver_features: drm::driver::FEAT_GEM,
         ioctls: T::IOCTLS.as_ptr(),
         num_ioctls: T::IOCTLS.len() as i32,
-        fops: &Self::GEM_FOPS,
+        fops: &Self::FOPS,
     };
 
-    const GEM_FOPS: bindings::file_operations = drm::gem::create_fops();
+    const FOPS: bindings::file_operations = T::FOPS;
 
     /// Create a new `drm::Device` for a `drm::Driver`.
     pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<ARef<Self>> {
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 5233bdebc9fc..79218c482fce 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -115,6 +115,12 @@ pub trait Driver {
 
     /// IOCTL list. See `kernel::drm::ioctl::declare_drm_ioctls!{}`.
     const IOCTLS: &'static [drm::ioctl::DrmIoctlDescriptor];
+
+    /// File operations for this driver.
+    ///
+    /// Override to replace or extend the default GEM file operations. The default
+    /// provides the standard GEM mmap handler via [`drm::gem::create_fops`].
+    const FOPS: bindings::file_operations = drm::gem::create_fops();
 }
 
 /// The registration type of a `drm::Device`.
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 75acda7ba500..de7222ee0542 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -348,7 +348,8 @@ impl<T: DriverObject> AllocImpl for Object<T> {
     };
 }
 
-pub(super) const fn create_fops() -> bindings::file_operations {
+/// Returns the default GEM [`bindings::file_operations`] for a DRM driver.
+pub const fn create_fops() -> bindings::file_operations {
     let mut fops: bindings::file_operations = pin_init::zeroed();
 
     fops.owner = core::ptr::null_mut();

-- 
2.53.0