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, 9 insertions, 0 deletions

diff --git a/linux/drivers/media/video/Kconfig b/linux/drivers/media/video/Kconfig
index e28e292fe..2dce16f86 100644
--- a/linux/drivers/media/video/Kconfig
+++ b/linux/drivers/media/video/Kconfig
@@ -72,6 +72,15 @@ config VIDEO_ADV_DEBUG
 	  V4L devices.
 	  In doubt, say N.
 
+config VIDEO_FIXED_MINOR_RANGES
+	bool "Enable old-style fixed minor ranges for video devices"
+	default n
+	---help---
+	  Say Y here to enable the old-style fixed-range minor assignments.
+	  Only useful if you rely on the old behavior and use mknod instead of udev.
+
+	  When in doubt, say N.
+
 config VIDEO_HELPER_CHIPS_AUTO
 	bool "Autoselect pertinent encoders/decoders and other helper chips"
 	default y