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

Sowjanya Komatineni
2020-04-30T20:10:10Z

On 4/30/20 1:06 PM, Dmitry Osipenko wrote:
> 30.04.2020 01:00, Sowjanya Komatineni пишет:
>> +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