[PATCH v2] drm: document that blobs are ref'counted

[Daniel Vetter]

On Wed, Nov 04, 2020 at 05:01:40PM +0000, Simon Ser wrote:
> User-space doesn't need to keep track of blobs that might be in use by
> the kernel. User-space can just destroy blobs as soon as they don't need
> them anymore.
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Signed-off-by: Daniel Stone <daniel at fooishbar.org>
> Reviewed-by: Jonas Ådahl <jadahl at gmail.com>
> Cc: Pekka Paalanen <ppaalanen at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  include/uapi/drm/drm_mode.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 863eda048265..5ad10ab2a577 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -924,6 +924,12 @@ struct drm_mode_create_blob {
>   * struct drm_mode_destroy_blob - Destroy user blob
>   * @blob_id: blob_id to destroy
>   * Destroy a user-created blob property.
> + *
> + * User-space can release blobs as soon as they do not need to refer to them by
> + * their blob object ID.  For instance, if you are using a MODE_ID blob in an
> + * atomic commit and you will not make another commit re-using the same ID, you
> + * can destroy the blob as soon as the commit has been issued, without waiting
> + * for it to complete.
>   */
>  struct drm_mode_destroy_blob {
>  	__u32 blob_id;
> -- 
> 2.29.2
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch