On 15/10/2025 14:00, Boris Brezillon wrote:
> Hook-up drm_gem_dmabuf_{begin,end}_cpu_access() to drm_gem_sync() so
> that drivers relying on the default prime_dmabuf_ops can still have
> a way to prepare for CPU accesses from outside the UMD.
>
> v2:
> - New commit
>
> v3:
> - Don't return an error on NOP syncs, and document that case in a
> comment
>
> Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Steven Price <[email protected]>
> ---
> drivers/gpu/drm/drm_prime.c | 42 +++++++++++++++++++++++++++++++++++++
> include/drm/drm_prime.h | 5 +++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 43a10b4af43a..30d495c70afb 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -823,6 +823,46 @@ int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct
> vm_area_struct *vma)
> }
> EXPORT_SYMBOL(drm_gem_dmabuf_mmap);
>
> +int drm_gem_dmabuf_begin_cpu_access(struct dma_buf *dma_buf,
> + enum dma_data_direction direction)
> +{
> + struct drm_gem_object *obj = dma_buf->priv;
> + enum drm_gem_object_access_flags access = DRM_GEM_OBJECT_CPU_ACCESS;
> +
> + /* begin_cpu_access(DMA_TO_DEVICE) is a NOP, the sync will happen
> + * in the end_cpu_access() path.
> + */
> + if (direction == DMA_FROM_DEVICE)
> + access |= DRM_GEM_OBJECT_READ_ACCESS;
> + else if (direction == DMA_BIDIRECTIONAL)
> + access |= DRM_GEM_OBJECT_RW_ACCESS;
> + else
> + return 0;
> +
> + return drm_gem_sync(obj, 0, obj->size, access);
> +}
> +EXPORT_SYMBOL(drm_gem_dmabuf_begin_cpu_access);
> +
> +int drm_gem_dmabuf_end_cpu_access(struct dma_buf *dma_buf,
> + enum dma_data_direction direction)
> +{
> + struct drm_gem_object *obj = dma_buf->priv;
> + enum drm_gem_object_access_flags access = DRM_GEM_OBJECT_DEV_ACCESS;
> +
> + /* end_cpu_access(DMA_FROM_DEVICE) is a NOP, the sync should have
> + * happened in the begin_cpu_access() path already.
> + */
> + if (direction == DMA_TO_DEVICE)
> + access |= DRM_GEM_OBJECT_READ_ACCESS;
> + else if (direction == DMA_BIDIRECTIONAL)
> + access |= DRM_GEM_OBJECT_RW_ACCESS;
> + else
> + return 0;
> +
> + return drm_gem_sync(obj, 0, obj->size, access);
> +}
> +EXPORT_SYMBOL(drm_gem_dmabuf_end_cpu_access);
> +
> static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
> .attach = drm_gem_map_attach,
> .detach = drm_gem_map_detach,
> @@ -832,6 +872,8 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops
> = {
> .mmap = drm_gem_dmabuf_mmap,
> .vmap = drm_gem_dmabuf_vmap,
> .vunmap = drm_gem_dmabuf_vunmap,
> + .begin_cpu_access = drm_gem_dmabuf_begin_cpu_access,
> + .end_cpu_access = drm_gem_dmabuf_end_cpu_access,
> };
>
> /**
> diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
> index f50f862f0d8b..052fba039bb6 100644
> --- a/include/drm/drm_prime.h
> +++ b/include/drm/drm_prime.h
> @@ -92,6 +92,11 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, struct
> iosys_map *map);
> int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct
> *vma);
> int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma);
>
> +int drm_gem_dmabuf_begin_cpu_access(struct dma_buf *dma_buf,
> + enum dma_data_direction direction);
> +int drm_gem_dmabuf_end_cpu_access(struct dma_buf *dma_buf,
> + enum dma_data_direction direction);
> +
> struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev,
> struct page **pages, unsigned int
> nr_pages);
> struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
