[PATCH 08/13] rust: drm/gem: add GEM object query helpers for debugfs

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

Add name(), refcount(), is_imported(), is_exported(), and mmap_offset()
to BaseObject so drivers can expose GEM state in debugfs.

Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
 rust/kernel/drm/gem/mod.rs | 49 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 276ba3c53475d..b6188c8873ece 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -21,9 +21,13 @@
     },
     error::to_result,
     prelude::*,
-    sync::aref::{
-        ARef,
-        AlwaysRefCounted, //
+    sync::{
+        aref::{
+            ARef,
+            AlwaysRefCounted, //
+        },
+        atomic::Relaxed,
+        Refcount, //
     },
     types::Opaque,
 };
@@ -177,6 +181,45 @@ fn size(&self) -> usize {
         unsafe { (*self.as_raw()).size }
     }
 
+    /// Returns the name of the object.
+    #[inline]
+    fn name(&self) -> i32 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
+        unsafe { (*self.as_raw()).name }
+    }
+
+    /// Returns the reference count of the object.
+    #[inline]
+    fn refcount(&self) -> u32 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
+        let raw_refcount = unsafe { &raw mut (*self.as_raw()).refcount }.cast::<Refcount>();
+        // SAFETY: `raw_refcount` has the same layout as `Refcount`.
+        let refcount = unsafe { &*raw_refcount };
+
+        refcount.as_atomic().load(Relaxed) as u32
+    }
+
+    /// Returns true if the object is imported.
+    #[inline]
+    fn is_imported(&self) -> bool {
+        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
+        !unsafe { (*self.as_raw()).import_attach }.is_null()
+    }
+
+    /// Returns true if the object is exported.
+    #[inline]
+    fn is_exported(&self) -> bool {
+        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
+        !unsafe { (*self.as_raw()).dma_buf }.is_null()
+    }
+
+    /// Returns the offset for mmap, or 0 if no offset has been allocated.
+    #[inline]
+    fn mmap_offset(&self) -> u64 {
+        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
+        unsafe { (*self.as_raw()).vma_node.vm_node.start }
+    }
+
     /// Creates a new handle for the object associated with a given `File`
     /// (or returns an existing one).
     fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>

-- 
2.43.0