[PATCH 07/13] rust: drm: add Device::primary_index()

[Alvin Sun <alvin.sun@linux.dev>]

Add primary_index() to return the primary minor index (e.g. the N in
/dev/dri/cardN). Needed by drivers to register per-device debugfs under
a unique directory name.

Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
 rust/kernel/drm/device.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index d7bb338efb9d8..268ac02e800fd 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -336,6 +336,16 @@ pub(crate) unsafe fn assume_ctx<NewCtx: DeviceContext>(&self) -> &Device<T, NewC
     }
 }
 
+impl<T: drm::Driver> Device<T, Registered> {
+    /// Returns the primary minor index (the number in `/dev/dri/cardN`).
+    #[inline]
+    pub fn primary_index(&self) -> u32 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a valid pointer to a `struct drm_device`.
+        let index = unsafe { (*(*self.as_raw()).primary).index };
+        index as u32
+    }
+}
+
 impl<T: drm::Driver> Deref for Device<T, Registered> {
     type Target = T::Data;
 

-- 
2.43.0