Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver

[Sowjanya Komatineni]

On 4/30/20 1:21 PM, Dmitry Osipenko wrote:
> 30.04.2020 23:09, Sowjanya Komatineni ÐÐÑÐÑ:
> > On 4/30/20 1:08 PM, Sowjanya Komatineni wrote:
> > > On 4/30/20 1:06 PM, Dmitry Osipenko wrote:
> > > > 30.04.2020 01:00, Sowjanya Komatineni ÐÐÑÐÑ:
> > > > > +static int chan_capture_kthread_start(void *data)
> > > > > +{
> > > > > +ÂÂÂ struct tegra_vi_channel *chan = data;
> > > > > +ÂÂÂ struct tegra_channel_buffer *buf;
> > > > > +ÂÂÂ int err = 0;
> > > > > +
> > > > > +ÂÂÂ set_freezable();
> > > > > +
> > > > > +ÂÂÂ while (1) {
> > > > > +ÂÂÂÂÂÂÂ try_to_freeze();
> > > > > +
> > > > > +ÂÂÂÂÂÂÂ /*
> > > > > +ÂÂÂÂÂÂÂÂ * Source is not streaming if error is non-zero.
> > > > > +ÂÂÂÂÂÂÂÂ * So, do not dequeue buffers on error and let the thread
> > > > > sleep
> > > > > +ÂÂÂÂÂÂÂÂ * till kthread stop signal is received.
> > > > > +ÂÂÂÂÂÂÂÂ */
> > > > > +ÂÂÂÂÂÂÂ wait_event_interruptible(chan->start_wait,
> > > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ kthread_should_stop() ||
> > > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (!list_empty(&chan->capture) &&
> > > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ !err));
> > > > ...
> > > > > +static void tegra_channel_buffer_queue(struct vb2_buffer *vb)
> > > > > +{
> > > > > +ÂÂÂ struct tegra_vi_channel *chan = vb2_get_drv_priv(vb->vb2_queue);
> > > > > +ÂÂÂ struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> > > > > +ÂÂÂ struct tegra_channel_buffer *buf = to_tegra_channel_buffer(vbuf);
> > > > > +
> > > > > +ÂÂÂ /* put buffer into the capture queue */
> > > > > +ÂÂÂ spin_lock(&chan->start_lock);
> > > > > +ÂÂÂ list_add_tail(&buf->queue, &chan->capture);
> > > > > +ÂÂÂ spin_unlock(&chan->start_lock);
> > > > > +
> > > > > +ÂÂÂ /* wait up kthread for capture */
> > > > > +ÂÂÂ wake_up_interruptible(&chan->start_wait);
> > > > > +}
> > > > The V4L doc says that buffers could be enqueued before streaming is
> > > > started. I guess it should be a trouble here, shouldn't it?
> > > >
> > > > https://elixir.bootlin.com/linux/v5.7-rc3/source/include/media/videobuf2-core.h#L379
> > > what trouble are you referring here?
> > >
> > > I dont think so as we set min buffers needed as 2 always there will be
> > > 2 per-queued buffers.
> > typo* pre-queued buffers before streaming start
> > > But buffers from this queue will be dequeued only when ready to
> > > processes in the capture thread
> I see now that the threads won't be running until start_streaming() is
> invoked, should be okay then.
ok. yes threads run only during streaming