[PATCH 3.12 062/107] media: media: v4l2-dev: fix video device index assignment

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

commit 6c3df5da67f1f53df78c7e20cd53a481dc28eade upstream.

The side effect of commit 1056e4388b045 ("v4l2-dev: Fix race condition on
__video_register_device") is the increased number of index value assigned
on video_device registration. Before that commit video_devices were
numbered from 0, after it, the indexes starts from 1, because get_index()
always count the device, which is being registered. Some device drivers
rely on video_device index number for internal purposes, i.e. s5p-mfc
driver stopped working after that patch. This patch restores the old method
of numbering the video_device indexes.

Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Acked-by: Ricardo Ribalda <ricardo.ribalda@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/media/v4l2-core/v4l2-dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -872,8 +872,8 @@ int __video_register_device(struct video
 
 	/* Should not happen since we thought this minor was free */
 	WARN_ON(video_device[vdev->minor] != NULL);
-	video_device[vdev->minor] = vdev;
 	vdev->index = get_index(vdev);
+	video_device[vdev->minor] = vdev;
 	mutex_unlock(&videodev_lock);
 
 	if (vdev->ioctl_ops)


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