On Thu, 2013-11-21 at 08:56 +0100, Hans Verkuil wrote:
> Hi Andy,
>
> As I mentioned in irc I have been working in this same area as well, so
> I'll take this patch and merge it in my tree and test it as well.
>
> I suspect that it might be easiest if I add the patch to my upcoming
> patch series in order to prevent merge conflicts. I'll know more later
> today.
Hi Hans,
That sounds good to me. :)
I have 4 comments on my own stuff below:
> On 11/21/2013 02:05 AM, Andy Walls wrote:
> > (This patch is RFC, because it was compiled and tested against kernel
> > v3.5)
> >
> > videobuf2 file I/O emulation assumed that buffers dequeued from the
> > driver would return in the order they were enqueued in the driver.
> >
> > Improve the file I/O emulator's book-keeping to remove this assumption.
> >
> > Also remove the, AFAICT, assumption that only read() calls would need to
> > dequeue a buffer from the driver.
Please remove the above sentence, it is incorrect.
> > Also set the buf->size properly, if a write() dequeues a buffer.
Please append: ", and the VB2_FILEIO_WRITE_IMMEDIATELY flag is set."
> > Signed-off-by: Andy Walls <awalls@xxxxxxxxxxxxxxxx>
> > Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> > Cc: PawelOsciak<pawel@xxxxxxxxxx>
> > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> >
> >
> > diff --git a/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c
> > index 9d4e9ed..f330aa4 100644
> > --- a/drivers/media/video/videobuf2-core.c
> > +++ b/drivers/media/video/videobuf2-core.c
> > @@ -1796,6 +1796,7 @@ struct vb2_fileio_data {
> > unsigned int dq_count;
> > unsigned int flags;
> > };
> > +#define FILEIO_INDEX_NOT_SET ((unsigned int) INT_MAX)
> >
> > /**
> > * __vb2_init_fileio() - initialize file io emulator
> > @@ -1889,6 +1890,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> > goto err_reqbufs;
> > fileio->bufs[i].queued = 1;
> > }
> > + fileio->index = FILEIO_INDEX_NOT_SET;
> >
> > /*
> > * Start streaming.
> > @@ -1975,15 +1977,11 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> > */
> > q->fileio = NULL;
> >
> > - index = fileio->index;
> > - buf = &fileio->bufs[index];
> > -
> > /*
> > * Check if we need to dequeue the buffer.
> > */
> > - if (buf->queued) {
> > - struct vb2_buffer *vb;
> > -
> > + index = fileio->index;
> > + if (index == FILEIO_INDEX_NOT_SET) {
> > /*
> > * Call vb2_dqbuf to get buffer back.
> > */
> > @@ -1997,12 +1995,19 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> > goto end;
> > fileio->dq_count += 1;
> >
> > + fileio->index = fileio->b.index;
> > + index = fileio->index;
> > + buf = &fileio->bufs[index];
> > +
> > /*
> > * Get number of bytes filled by the driver
> > */
> > - vb = q->bufs[index];
> > - buf->size = vb2_get_plane_payload(vb, 0);
> > + buf->pos = 0;
> > buf->queued = 0;
> > + buf->size = read ? vb2_get_plane_payload(q->bufs[index], 0)
> > + : vb2_plane_size(q->bufs[index], 0);
> > + } else {
> > + buf = &fileio->bufs[index];
> > }
> >
> > /*
> > @@ -2070,13 +2075,28 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> > */
> > buf->pos = 0;
> > buf->queued = 1;
> > - buf->size = q->bufs[0]->v4l2_planes[0].length;
> > + buf->size = vb2_plane_size(q->bufs[index], 0);
> > fileio->q_count += 1;
> >
> > /*
> > - * Switch to the next buffer
> > + * Decide on the next buffer
> > */
> > - fileio->index = (index + 1) % q->num_buffers;
> > + if (read || (q->num_buffers == 1)) {
Change to
if (read || (fileio->q_count >= q->num_buffers))
After the initial write() calls queue all the buffers, steady state is
all the buffers queued in the driver. At steady state, the do-while
loop below is wasted effort. This change to the if() condition avoids
that wasted effort, except for briefly after every roll-over of
fileio->q_count.
> > + /* Use the next buffer the driver provides back */
> > + fileio->index = FILEIO_INDEX_NOT_SET;
> > + } else {
> > + /* Prefer a buffer that is not quequed in the driver */
s/quequed/queued/
> > + int initial_index = fileio->index;
> > + fileio->index = FILEIO_INDEX_NOT_SET;
> > + do {
> > + if (++index == q->num_buffers)
> > + index = 0;
> > + if (!fileio->bufs[index].queued) {
> > + fileio->index = index;
> > + break;
> > + }
> > + } while (index != initial_index);
> > + }
> > /*
> > * Start streaming if required.
> >
> >
Regards,
Andy
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