On 27/11/2020 15:30, Sergey Senozhatsky wrote:
> On (20/11/27 13:59), Hans Verkuil wrote:
>>
>> I think this needs a comment, basically explaining what you said in
>> the commit log. It's not obvious from the code that this is a
>> workaround.
>
> Something like this?
Yes.
BTW, wouldn't it be sufficient to change this code to:
if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
vb->need_cache_sync_on_prepare = 1;
vb->need_cache_sync_on_finish = 1;
}
Or am I missing something?
DVB drivers do not set this flag, and even for DVB cache sync shouldn't be
needed for DMABUF, right?
Regards,
Hans
>
> ---
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> b/drivers/media/common/videobuf2/videobuf2-core.c
> index 5499013cf82e..21b2b0ae3629 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -414,6 +414,16 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum
> vb2_memory memory,
> vb->index = q->num_buffers + buffer;
> vb->type = q->type;
> vb->memory = memory;
> + /*
> + * A workaround fix. We need to set these flags here so that
> + * videobuf2 core will always call ->prepare()/->finish()
> + * cache sync/flush on vb2 buffers. Otherwise, for backends
> + * that don't rely on V4L2 (perhaps dvb) these flags will
> + * always be false and, hence, videobuf2 core will skip cache
> + * sync/flush operations.
> + */
> + vb->need_cache_sync_on_prepare = 1;
> + vb->need_cache_sync_on_finish = 1;
> for (plane = 0; plane < num_planes; ++plane) {
> vb->planes[plane].length = plane_sizes[plane];
> vb->planes[plane].min_length = plane_sizes[plane];
>
