We just added an export() callback that GEM objects can implement, but
without any way of actually exporting a DmaBuf<T>. So let's add one by
introducing bindings for drm_gem_prime_export().
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
rust/kernel/dma_buf.rs | 1 -
rust/kernel/drm/gem/mod.rs | 24 +++++++++++++++++++++++-
2 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/dma_buf.rs b/rust/kernel/dma_buf.rs
index a66829afcd129..a2086918efd17 100644
--- a/rust/kernel/dma_buf.rs
+++ b/rust/kernel/dma_buf.rs
@@ -20,7 +20,6 @@ unsafe impl Send for DmaBuf {}
// SAFETY: `struct dma_buf` is thread-safe
unsafe impl Sync for DmaBuf {}
-#[expect(unused)]
impl DmaBuf {
/// Convert from a `*mut bindings::dma_buf` to a [`DmaBuf`].
///
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 1ac25fc6d527b..75ffd5541e84c 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -11,7 +11,7 @@
bindings, dma_buf,
drm::driver::{AllocImpl, AllocOps},
drm::{self, private::Sealed},
- error::{to_result, Result},
+ error::{from_err_ptr, to_result, Result},
prelude::*,
types::{ARef, AlwaysRefCounted, Opaque},
};
@@ -225,6 +225,28 @@ fn lookup_handle<D, F, O>(file: &drm::File<F>, handle:
u32) -> Result<ARef<Self>
Ok(unsafe { ARef::from_raw(obj.into()) })
}
+ /// Export a [`DmaBuf`] for this GEM object using the DRM prime helper
library.
+ ///
+ /// `flags` should be a set of flags from
[`fs::file::flags`](kernel::fs::file::flags).
+ fn prime_export(&self, flags: u32) -> Result<DmaBuf<Self>> {
+ // SAFETY: `as_raw()` always returns a valid pointer to an initialized
`drm_gem_object`.
+ let dma_ptr = unsafe { bindings::drm_gem_prime_export(self.as_raw(),
flags as i32) };
+
+ // `drm_gem_prime_export()` returns either an error pointer, or a
valid pointer to an
+ // initialized `dma_buf` on success.
+ let dma_ptr = from_err_ptr(dma_ptr)?;
+
+ // SAFETY:
+ // - We checked that dma_ptr is not an error, so it must point to an
initialized dma_buf
+ // - We used drm_gem_prime_export(), so `dma_ptr` will remain valid
until a call to
+ // `drm_gem_prime_release()` which we don't call here.
+ let dma_buf = unsafe { dma_buf::DmaBuf::from_raw(dma_ptr) };
+
+ // INVARIANT: We used drm_gem_prime_export() to create this dma_buf,
fulfilling the
+ // invariant that this dma_buf came from a GEM object of type `Self`.
+ Ok(DmaBuf(dma_buf.into(), PhantomData))
+ }
+
/// Creates an mmap offset to map the object from userspace.
fn create_mmap_offset(&self) -> Result<u64> {
// SAFETY: The arguments are valid per the type invariant.
--
2.50.0
