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 lyude@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.