On 09/16/14 15:50, Mauro Carvalho Chehab wrote: > Em Tue, 16 Sep 2014 11:28:16 +0200 > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > >> (My proposal to fix this. Note that it is untested, I plan to do that this >> evening) >> >> Commit 9241650d62f7 broke vbi capture applications that expect POLLERR to be >> returned if STREAMON wasn't called. >> >> Rather than checking whether buffers were queued AND vb2 was not yet streaming, >> just check whether streaming is in progress and return POLLERR if not. >> >> This change makes it impossible to poll in one thread and call STREAMON in >> another, but doing that breaks existing applications and is also not according >> to the spec. So be it. >> >> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> >> >> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c >> index 7e6aff6..0452fb2 100644 >> --- a/drivers/media/v4l2-core/videobuf2-core.c >> +++ b/drivers/media/v4l2-core/videobuf2-core.c >> @@ -2583,10 +2583,10 @@ unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) >> } >> >> /* >> - * There is nothing to wait for if no buffer has been queued and the >> - * queue isn't streaming, or if the error flag is set. >> + * There is nothing to wait for if the queue isn't streaming, or if >> + * the error flag is set. >> */ >> - if ((list_empty(&q->queued_list) && !vb2_is_streaming(q)) || q->error) >> + if (!vb2_is_streaming(q) || q->error) >> return res | POLLERR; > > This makes the code even more different than what VB1 does. I suspect > that this will likely cause even more regressions. > > The following (untested) patch seems to be what matches best what VB1 > does, and are likely to cause less harm, but needs test of course. > > diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c > index 5b808e25fc09..0d86526cbcb0 100644 > --- a/drivers/media/v4l2-core/videobuf2-core.c > +++ b/drivers/media/v4l2-core/videobuf2-core.c > @@ -2586,6 +2586,9 @@ unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) > * There is nothing to wait for if no buffer has been queued and the > * queue isn't streaming, or if the error flag is set. > */ > + if (!vb2_is_streaming(q)) > + vb2_internal_streamon(q, q->type); > + As mentioned in my previous email, this is certainly not what vb1 does. VB1 returns POLLERR and does not start streaming, that's what I saw when debugging this yesterday. The automatic streaming when poll is called is valid only if REQBUFS was never called since it assumes read() mode. Regards, Hans > if ((list_empty(&q->queued_list) && !vb2_is_streaming(q)) || q->error) > return res | POLLERR; > > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
