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/drm/gem/mod.rs | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs index ef697f323e52c..ee74b9bdb7a1f 100644 --- a/rust/kernel/drm/gem/mod.rs +++ b/rust/kernel/drm/gem/mod.rs @@ -225,6 +225,29 @@ 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 a `drm_gem_object`. + // - `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(unsafe { + bindings::drm_gem_prime_export(self.as_raw(), flags as _) + })?; + + // 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::as_ref(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.