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    SubjectRe: [PATCH v6 1/6] [media] vb2: add is_unordered callback for drivers
    2017-12-21 Mauro Carvalho Chehab <mchehab@osg.samsung.com>:

    > Em Mon, 11 Dec 2017 16:27:36 -0200
    > Gustavo Padovan <gustavo@padovan.org> escreveu:
    >
    > > From: Gustavo Padovan <gustavo.padovan@collabora.com>
    > >
    > > Explicit synchronization benefits a lot from ordered queues, they fit
    > > better in a pipeline with DRM for example so create a opt-in way for
    > > drivers notify videobuf2 that the queue is unordered.
    > >
    > > Drivers don't need implement it if the queue is ordered.
    > >
    > > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
    > > ---
    > > include/media/videobuf2-core.h | 5 +++++
    > > 1 file changed, 5 insertions(+)
    > >
    > > diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
    > > index ef9b64398c8c..eddb38a2a2f3 100644
    > > --- a/include/media/videobuf2-core.h
    > > +++ b/include/media/videobuf2-core.h
    > > @@ -368,6 +368,9 @@ struct vb2_buffer {
    > > * callback by calling vb2_buffer_done() with either
    > > * %VB2_BUF_STATE_DONE or %VB2_BUF_STATE_ERROR; may use
    > > * vb2_wait_for_all_buffers() function
    > > + * @is_unordered: tell if the queue format is unordered. The default is
    > > + * assumed to be ordered and this function only needs to
    > > + * be implemented for unordered queues.
    > > * @buf_queue: passes buffer vb to the driver; driver may start
    > > * hardware operation on this buffer; driver should give
    > > * the buffer back by calling vb2_buffer_done() function;
    > > @@ -391,6 +394,7 @@ struct vb2_ops {
    > >
    > > int (*start_streaming)(struct vb2_queue *q, unsigned int count);
    > > void (*stop_streaming)(struct vb2_queue *q);
    > > + int (*is_unordered)(struct vb2_queue *q);
    > >
    > > void (*buf_queue)(struct vb2_buffer *vb);
    > > };
    > > @@ -564,6 +568,7 @@ struct vb2_queue {
    > > u32 cnt_wait_finish;
    > > u32 cnt_start_streaming;
    > > u32 cnt_stop_streaming;
    > > + u32 cnt_is_unordered;
    >
    > If I understand, this is just a bit, right?
    >
    > if so, better to declare it as:
    >
    > u32 cnt_is_unordered : 1;

    no, is_unordered() is a vb2 callback to ask drivers if their current
    queue is not ordered and cnt_is_unordered is the counter of how many
    times this callback was called. This happens for all vb2 callbacks, see
    the other counters above, so I decided to add one for is_unordered() as
    well.

    Gustavo

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