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

[Sowjanya Komatineni]

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)
> > +{
> > +	struct tegra_vi_channel *chan = data;
> > +	struct tegra_channel_buffer *buf;
> > +	int err = 0;
> > +
> > +	set_freezable();
> > +
> > +	while (1) {
> > +		try_to_freeze();
> > +
> > +		/*
> > +		 * Source is not streaming if error is non-zero.
> > +		 * So, do not dequeue buffers on error and let the thread sleep
> > +		 * till kthread stop signal is received.
> > +		 */
> > +		wait_event_interruptible(chan->start_wait,
> > +					 kthread_should_stop() ||
> > +					 (!list_empty(&chan->capture) &&
> > +					 !err));
> ...
> > +static void tegra_channel_buffer_queue(struct vb2_buffer *vb)
> > +{
> > +	struct tegra_vi_channel *chan = vb2_get_drv_priv(vb->vb2_queue);
> > +	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> > +	struct tegra_channel_buffer *buf = to_tegra_channel_buffer(vbuf);
> > +
> > +	/* put buffer into the capture queue */
> > +	spin_lock(&chan->start_lock);
> > +	list_add_tail(&buf->queue, &chan->capture);
> > +	spin_unlock(&chan->start_lock);
> > +
> > +	/* wait up kthread for capture */
> > +	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.

But buffers from this queue will be dequeued only when ready to 
processes in the capture thread