v4l: disconnect kernel number from minor

From: Hans Verkuil <hverkuil@xs4all.nl>

The v4l core creates four different video devices (video, vbi, radio, vtx)
and each has its own range of minor numbers. However, modern devices keep
increasing the number of devices that they need so a maximum of 64 video
devices will not be enough in the future. In addition this scheme makes
it very hard to add new device types.

This patch disconnects the kernel number allocation (e.g. video0, video1,
etc.) from the actual minor number (just pick the first free minor).

This allows for much more flexibility in the future. However, it does
require the use of udev. For those who cannot use udev a new CONFIG option
was created that changes the allocation scheme back to the old behavior.

Thanks to Greg KH for suggesting this approach during the 2008 LPC.

In addition, several bugs were fixed in the ivtv and cx18 drivers: these
drivers try to allocate specific kernel numbers but that scheme contained
a bug which caused what should have been e.g. video17 to appear as e.g.
video2.

Priority: normal

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

1 files changed, 3 insertions, 5 deletions

diff --git a/linux/drivers/media/video/em28xx/em28xx-video.c b/linux/drivers/media/video/em28xx/em28xx-video.c
index e94b50f00..2d0cd4abc 100644
--- a/linux/drivers/media/video/em28xx/em28xx-video.c
+++ b/linux/drivers/media/video/em28xx/em28xx-video.c
@@ -1657,8 +1657,7 @@ static void em28xx_release_resources(struct em28xx *dev)
 	/*FIXME: I2C IR should be disconnected */
 
 	em28xx_info("V4L2 devices /dev/video%d and /dev/vbi%d deregistered\n",
-				dev->vdev->minor-MINOR_VFL_TYPE_GRABBER_MIN,
-				dev->vbi_dev->minor-MINOR_VFL_TYPE_VBI_MIN);
+				dev->vdev->num, dev->vbi_dev->num);
 	list_del(&dev->devlist);
 	if (dev->sbutton_input_dev)
 		em28xx_deregister_snapshot_button(dev);
@@ -2138,8 +2137,7 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
 	video_mux(dev, 0);
 
 	em28xx_info("V4L2 device registered as /dev/video%d and /dev/vbi%d\n",
-				dev->vdev->minor-MINOR_VFL_TYPE_GRABBER_MIN,
-				dev->vbi_dev->minor-MINOR_VFL_TYPE_VBI_MIN);
+				dev->vdev->num, dev->vbi_dev->num);
 
 	mutex_lock(&em28xx_extension_devlist_lock);
 	if (!list_empty(&em28xx_extension_devlist)) {
@@ -2350,7 +2348,7 @@ static void em28xx_usb_disconnect(struct usb_interface *interface)
 		em28xx_warn
 		    ("device /dev/video%d is open! Deregistration and memory "
 		     "deallocation are deferred on close.\n",
-				dev->vdev->minor-MINOR_VFL_TYPE_GRABBER_MIN);
+				dev->vdev->num);
 
 		dev->state |= DEV_MISCONFIGURED;
 		em28xx_uninit_isoc(dev);