v4l: warn when desired devnodenr is in use & add _no_warn function

From: Hans Verkuil <hverkuil@xs4all.nl>

Warn when the desired device node number is already in use, except when
the new video_register_device_no_warn function is called since in some
use-cases that warning is not relevant.

Priority: normal

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>

3 files changed, 21 insertions, 3 deletions

diff --git a/linux/drivers/media/video/cx18/cx18-streams.c b/linux/drivers/media/video/cx18/cx18-streams.c
index 816d70cc2..dabe3fadc 100644
--- a/linux/drivers/media/video/cx18/cx18-streams.c
+++ b/linux/drivers/media/video/cx18/cx18-streams.c
@@ -250,7 +250,7 @@ static int cx18_reg_dev(struct cx18 *cx, int type)
 	video_set_drvdata(s->video_dev, s);
 
 	/* Register device. First try the desired minor, then any free one. */
-	ret = video_register_device(s->video_dev, vfl_type, num);
+	ret = video_register_device_no_warn(s->video_dev, vfl_type, num);
 	if (ret < 0) {
 		CX18_ERR("Couldn't register v4l2 device for %s (device node number %d)\n",
 			s->name, num);
diff --git a/linux/drivers/media/video/ivtv/ivtv-streams.c b/linux/drivers/media/video/ivtv/ivtv-streams.c
index 234000352..67699e3f2 100644
--- a/linux/drivers/media/video/ivtv/ivtv-streams.c
+++ b/linux/drivers/media/video/ivtv/ivtv-streams.c
@@ -261,7 +261,7 @@ static int ivtv_reg_dev(struct ivtv *itv, int type)
 	video_set_drvdata(s->vdev, s);
 
 	/* Register device. First try the desired minor, then any free one. */
-	if (video_register_device(s->vdev, vfl_type, num)) {
+	if (video_register_device_no_warn(s->vdev, vfl_type, num)) {
 		IVTV_ERR("Couldn't register v4l2 device for %s (device node number %d)\n",
 				s->name, num);
 		video_device_release(s->vdev);
diff --git a/linux/drivers/media/video/v4l2-dev.c b/linux/drivers/media/video/v4l2-dev.c
index 9a9fc1c83..a6d761dec 100644
--- a/linux/drivers/media/video/v4l2-dev.c
+++ b/linux/drivers/media/video/v4l2-dev.c
@@ -420,6 +420,8 @@ static int get_index(struct video_device *vdev)
  *	@type: type of device to register
  *	@nr:   which device node number (0 == /dev/video0, 1 == /dev/video1, ...
  *             -1 == first free)
+ *	@warn_if_nr_in_use: warn if the desired device node number
+ *	       was already in use and another number was chosen instead.
  *
  *	The registration code assigns minor numbers and device node numbers
  *	based on the requested type and registers the new device node with
@@ -439,7 +441,8 @@ static int get_index(struct video_device *vdev)
  *
  *	%VFL_TYPE_RADIO - A radio card
  */
-int video_register_device(struct video_device *vdev, int type, int nr)
+static int __video_register_device(struct video_device *vdev, int type, int nr,
+		int warn_if_nr_in_use)
 {
 	int i = 0;
 	int ret;
@@ -615,6 +618,10 @@ int video_register_device(struct video_device *vdev, int type, int nr)
 	   reference to the device goes away. */
 	vdev->dev.release = v4l2_device_release;
 
+	if (nr != -1 && nr != vdev->num && warn_if_nr_in_use)
+		printk(KERN_WARNING "%s: requested %s%d, got %s%d\n",
+				__func__, name_base, nr, name_base, vdev->num);
+
 	/* Part 5: Activate this minor. The char device can now be used. */
 	mutex_lock(&videodev_lock);
 	video_device[vdev->minor] = vdev;
@@ -631,8 +638,19 @@ cleanup:
 	vdev->minor = -1;
 	return ret;
 }
+
+int video_register_device(struct video_device *vdev, int type, int nr)
+{
+	return __video_register_device(vdev, type, nr, 1);
+}
 EXPORT_SYMBOL(video_register_device);
 
+int video_register_device_no_warn(struct video_device *vdev, int type, int nr)
+{
+	return __video_register_device(vdev, type, nr, 0);
+}
+EXPORT_SYMBOL(video_register_device_no_warn);
+
 /**
  *	video_unregister_device - unregister a video4linux device
  *	@vdev: the device to unregister