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SubjectRe: [PATCHv3 01/11] videobuf2: add cache management members
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On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> Extend vb2_buffer and vb2_queue structs with cache management
> members.
>
> V4L2 UAPI already contains two buffer flags which user-space,
> supposedly, can use to control buffer cache sync:
>
> - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
> - V4L2_BUF_FLAG_NO_CACHE_CLEAN
>
> None of these, however, do anything at the moment. This patch
> set is intended to change it.
>
> Since user-space cache management hints are supposed to be
> implemented on a per-buffer basis we need to extend vb2_buffer
> struct with two new memebers ->need_cache_sync_on_prepare and

memebers -> members

Regards,

Hans

> ->need_cache_sync_on_finish, which will store corresponding
> user-space hints.
>
> In order to preserve the existing behaviour, user-space cache
> managements flags will be handled only by those drivers that
> permit user-space cache hints. That's the purpose of vb2_queue
> ->allow_cache_hints member. Driver must set ->allow_cache_hints
> during queue initialisation to enable cache management hints
> mechanism.
>
> Only drivers that set ->allow_cache_hints during queue initialisation
> will handle user-space cache management hints. Otherwise hints
> will be ignored.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
> include/media/videobuf2-core.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index a2b2208b02da..4a19170672ac 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -263,6 +263,10 @@ struct vb2_buffer {
> * after the 'buf_finish' op is called.
> * copied_timestamp: the timestamp of this capture buffer was copied
> * from an output buffer.
> + * need_cache_sync_on_prepare: when set buffer's ->prepare() function
> + * performs cache sync/invalidation.
> + * need_cache_sync_on_finish: when set buffer's ->finish() function
> + * performs cache sync/invalidation.
> * queued_entry: entry on the queued buffers list, which holds
> * all buffers queued from userspace
> * done_entry: entry on the list that stores all buffers ready
> @@ -273,6 +277,8 @@ struct vb2_buffer {
> unsigned int synced:1;
> unsigned int prepared:1;
> unsigned int copied_timestamp:1;
> + unsigned int need_cache_sync_on_prepare:1;
> + unsigned int need_cache_sync_on_finish:1;
>
> struct vb2_plane planes[VB2_MAX_PLANES];
> struct list_head queued_entry;
> @@ -491,6 +497,9 @@ struct vb2_buf_ops {
> * @uses_requests: requests are used for this queue. Set to 1 the first time
> * a request is queued. Set to 0 when the queue is canceled.
> * If this is 1, then you cannot queue buffers directly.
> + * @allow_cache_hints: when set user-space can pass cache management hints in
> + * order to skip cache flush/invalidation on ->prepare() or/and
> + * ->finish().
> * @lock: pointer to a mutex that protects the &struct vb2_queue. The
> * driver can set this to a mutex to let the v4l2 core serialize
> * the queuing ioctls. If the driver wants to handle locking
> @@ -564,6 +573,7 @@ struct vb2_queue {
> unsigned requires_requests:1;
> unsigned uses_qbuf:1;
> unsigned uses_requests:1;
> + unsigned allow_cache_hints:1;
>
> struct mutex *lock;
> void *owner;
>

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