[PATCH v4 3/9] rust: helpers: Add bindings/wrappers for dma_resv_lock

[PATCH v4 3/9] rust: helpers: Add bindings/wrappers for dma_resv_lock

[Lyude Paul]

From: Asahi Lina <lina@asahilina.net>

This is just for basic usage in the DRM shmem abstractions for implied
locking, not intended as a full DMA Reservation abstraction yet.

Signed-off-by: Asahi Lina <lina@asahilina.net>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 rust/bindings/bindings_helper.h |  1 +
 rust/helpers/dma-resv.c         | 13 +++++++++++++
 rust/helpers/helpers.c          |  1 +
 3 files changed, 15 insertions(+)
 create mode 100644 rust/helpers/dma-resv.c

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 2e43c66635a2c..07f79e125c329 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -48,6 +48,7 @@
 #include <linux/cpumask.h>
 #include <linux/cred.h>
 #include <linux/debugfs.h>
+#include <linux/dma-resv.h>
 #include <linux/device/faux.h>
 #include <linux/dma-direction.h>
 #include <linux/dma-mapping.h>
diff --git a/rust/helpers/dma-resv.c b/rust/helpers/dma-resv.c
new file mode 100644
index 0000000000000..05501cb814513
--- /dev/null
+++ b/rust/helpers/dma-resv.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-resv.h>
+
+int rust_helper_dma_resv_lock(struct dma_resv *obj, struct ww_acquire_ctx *ctx)
+{
+	return dma_resv_lock(obj, ctx);
+}
+
+void rust_helper_dma_resv_unlock(struct dma_resv *obj)
+{
+	dma_resv_unlock(obj);
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 551da6c9b5064..36d40f911345c 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -25,6 +25,7 @@
 #include "cred.c"
 #include "device.c"
 #include "dma.c"
+#include "dma-resv.c"
 #include "drm.c"
 #include "err.c"
 #include "irq.c"
-- 
2.51.0

Re: [PATCH v4 3/9] rust: helpers: Add bindings/wrappers for dma_resv_lock

[Alice Ryhl]

On Thu, Oct 16, 2025 at 05:08:16PM -0400, Lyude Paul wrote:
> From: Asahi Lina <lina@asahilina.net>
> 
> This is just for basic usage in the DRM shmem abstractions for implied
> locking, not intended as a full DMA Reservation abstraction yet.
> 
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> Signed-off-by: Lyude Paul <lyude@redhat.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

[PATCH v4 4/9] rust: drm: gem: Add raw_dma_resv() function

[Lyude Paul]

For retrieving a pointer to the struct dma_resv for a given GEM object. We
also introduce it in a new trait, BaseObjectPrivate, which we automatically
implement for all gem objects and don't expose to users outside of the
crate.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 rust/kernel/drm/gem/mod.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 981fbb931e952..760fcd61da0b7 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -199,6 +199,18 @@ fn create_mmap_offset(&self) -> Result<u64> {
 
 impl<T: IntoGEMObject> BaseObject for T {}
 
+/// Crate-private base operations shared by all GEM object classes.
+#[expect(unused)]
+pub(crate) trait BaseObjectPrivate: IntoGEMObject {
+    /// Return a pointer to this object's dma_resv.
+    fn raw_dma_resv(&self) -> *mut bindings::dma_resv {
+        // SAFETY: `as_gem_obj()` always returns a valid pointer to the base DRM gem object
+        unsafe { (*self.as_raw()).resv }
+    }
+}
+
+impl<T: IntoGEMObject> BaseObjectPrivate for T {}
+
 /// A base GEM object.
 ///
 /// Invariants
-- 
2.51.0