media: tegra-video: Implement V4L2 device notify callback

Implement V4L2 device notify callback to handle
V4L2_EVENT_SOURCE_CHANGE event from subdevices.

HDMI-to-CSI bridge drivers trigger V4L2_EVENT_SOURCE_CHANGE when
source DV timing changes are detected or when HDMI hotplug happens.

Runtime source parameter changes during active streaming is not
allowed and Tegra video driver calls vb2_queue_error to signal a
fatal error if a notification of this event happens during an active
streaming.
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/tegra-video/vi.c

@@ -1636,6 +1636,9 @@ static int tegra_vi_graph_notify_complete(struct v4l2_async_notifier *notifier)
 
 	v4l2_set_subdev_hostdata(subdev, chan);
 
+	subdev = tegra_channel_get_remote_source_subdev(chan);
+	v4l2_set_subdev_hostdata(subdev, chan);
+
 	return 0;
 
 unregister_video:

drivers/staging/media/tegra-video/video.c

@@ -7,6 +7,8 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 
+#include <media/v4l2-event.h>
+
 #include "video.h"
 
 static void tegra_v4l2_dev_release(struct v4l2_device *v4l2_dev)
@@ -24,6 +26,21 @@ static void tegra_v4l2_dev_release(struct v4l2_device *v4l2_dev)
 	kfree(vid);
 }
 
+static void tegra_v4l2_dev_notify(struct v4l2_subdev *sd,
+				  unsigned int notification, void *arg)
+{
+	struct tegra_vi_channel *chan;
+	const struct v4l2_event *ev = arg;
+
+	if (notification != V4L2_DEVICE_NOTIFY_EVENT)
+		return;
+
+	chan = v4l2_get_subdev_hostdata(sd);
+	v4l2_event_queue(&chan->video, arg);
+	if (ev->type == V4L2_EVENT_SOURCE_CHANGE && vb2_is_streaming(&chan->queue))
+		vb2_queue_error(&chan->queue);
+}
+
 static int host1x_video_probe(struct host1x_device *dev)
 {
 	struct tegra_video_device *vid;
@@ -49,6 +66,7 @@ static int host1x_video_probe(struct host1x_device *dev)
 
 	vid->v4l2_dev.mdev = &vid->media_dev;
 	vid->v4l2_dev.release = tegra_v4l2_dev_release;
+	vid->v4l2_dev.notify = tegra_v4l2_dev_notify;
 	ret = v4l2_device_register(&dev->dev, &vid->v4l2_dev);
 	if (ret < 0) {
 		dev_err(&dev->dev,