On 15/10/2025 14:00, Boris Brezillon wrote:
> Prepare things for standardizing synchronization around CPU accesses
> of GEM buffers. This will be used to provide default
> drm_gem_dmabuf_{begin,end}_cpu_access() implementations, and provide
> a way for drivers to add their own ioctls to synchronize CPU
> writes/reads when they can't do it directly from userland.
>
> v2:
> - New commit
>
> v3:
> - No changes
>
> Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Steven Price <[email protected]>
> ---
> drivers/gpu/drm/drm_gem.c | 10 +++++++++
> include/drm/drm_gem.h | 45 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 55 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index a1a9c828938b..a1431e4f2404 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1333,6 +1333,16 @@ void drm_gem_vunmap(struct drm_gem_object *obj, struct
> iosys_map *map)
> }
> EXPORT_SYMBOL(drm_gem_vunmap);
>
> +int drm_gem_sync(struct drm_gem_object *obj, size_t offset, size_t size,
> + enum drm_gem_object_access_flags access)
> +{
> + if (obj->funcs->sync)
> + return obj->funcs->sync(obj, offset, size, access);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_gem_sync);
> +
> /**
> * drm_gem_lock_reservations - Sets up the ww context and acquires
> * the lock on an array of GEM objects.
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 8d48d2af2649..1c33e59ab305 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -66,6 +66,33 @@ enum drm_gem_object_status {
> DRM_GEM_OBJECT_ACTIVE = BIT(2),
> };
>
> +/**
> + * enum drm_gem_object_status - bitmask describing GEM access types to
> prepare for
> + */
> +enum drm_gem_object_access_flags {
> + /** @DRM_GEM_OBJECT_CPU_ACCESS: Prepare for a CPU access. */
> + DRM_GEM_OBJECT_CPU_ACCESS = 0,
> +
> + /** @DRM_GEM_OBJECT_DEV_ACCESS: Prepare for a device access. */
> + DRM_GEM_OBJECT_DEV_ACCESS = BIT(0),
> +
> + /** @DRM_GEM_OBJECT_ACCESSOR_MASK: Mask used to check the entity doing
> the access. */
> + DRM_GEM_OBJECT_ACCESSOR_MASK = BIT(0),
> +
> + /** @DRM_GEM_OBJECT_READ_ACCESS: Prepare for read-only accesses. */
> + DRM_GEM_OBJECT_READ_ACCESS = BIT(1),
> +
> + /** @DRM_GEM_OBJECT_WRITE_ACCESS: Prepare for write-only accesses. */
> + DRM_GEM_OBJECT_WRITE_ACCESS = BIT(2),
> +
> + /** @DRM_GEM_OBJECT_RW_ACCESS: Prepare for a read/write accesses. */
> + DRM_GEM_OBJECT_RW_ACCESS = DRM_GEM_OBJECT_READ_ACCESS |
> + DRM_GEM_OBJECT_WRITE_ACCESS,
> +
> + /** @DRM_GEM_OBJECT_ACCESS_TYPE_MASK: Mask used to check the access
> type. */
> + DRM_GEM_OBJECT_ACCESS_TYPE_MASK = DRM_GEM_OBJECT_RW_ACCESS,
> +};
> +
> /**
> * struct drm_gem_object_funcs - GEM object functions
> */
> @@ -191,6 +218,21 @@ struct drm_gem_object_funcs {
> */
> int (*mmap)(struct drm_gem_object *obj, struct vm_area_struct *vma);
>
> + /**
> + * @sync:
> + *
> + * Prepare for CPU/device access. This can involve migration of
> + * a buffer to the system-RAM/VRAM, or for UMA, flushing/invalidating
> + * the CPU caches. The range can be used to optimize the synchronization
> + * when possible.
> + *
> + * Returns 0 on success, -errno otherwise.
> + *
> + * This callback is optional.
> + */
> + int (*sync)(struct drm_gem_object *obj, size_t offset, size_t size,
> + enum drm_gem_object_access_flags access);
> +
> /**
> * @evict:
> *
> @@ -559,6 +601,9 @@ void drm_gem_unlock(struct drm_gem_object *obj);
> int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map);
> void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map);
>
> +int drm_gem_sync(struct drm_gem_object *obj, size_t offset, size_t size,
> + enum drm_gem_object_access_flags access);
> +
> int drm_gem_objects_lookup(struct drm_file *filp, void __user *bo_handles,
> int count, struct drm_gem_object ***objs_out);
> struct drm_gem_object *drm_gem_object_lookup(struct drm_file *filp, u32
> handle);
