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

Sowjanya Komatineni
2020-04-30T20:11:28Z

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 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.
typo* pre-queued buffers before streaming start
>
> But buffers from this queue will be dequeued only when ready to
> processes in the capture thread
>