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

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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





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