Re: assigning specific /dev/videoN to specific USB webcams

Newsgroups	comp.os.linux.misc
From	Eric Pozharski <whynot@pozharski.name>
Subject	Re: assigning specific /dev/videoN to specific USB webcams
References	<ki552n$nat$1@dont-email.me>
Message-ID	<slrnklipms.9ir.whynot@orphan.zombinet> (permalink)
Date	2013-04-01 13:52 +0300
Organization	SunSITE.dk - Supporting Open source

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with <ki552n$nat$1@dont-email.me> J G Miller wrote:
>
> Is it possible to create a udev rule to assign specific
> /dev/videoN numbers to USB  webcams. 

If my reading of devices.txt is correct then /dev/videoN is real
character special and supplied by kernel itself.  Then, I believe,
answer is -- no.  Quoting udev(7):

	Also, as a temporary workaround, this is what a device node
	should be named; usually the kernel provides the defined node
	name or creates and removes the node before udev even receives
	any event.  Changing the node name from the kernel's default
	creates inconsistencies and is not supported. If the kernel and
	NAME specify different names, an error is logged. udev is only
	expected to handle device node permissions and to create
	additional symlinks, not to change kernel-provided device node
	names. Instead of renaming a device node, SYMLINK should be
	used. However, symlink names must never conflict with device
	node names, as that would result in unpredictable behavior.

Shortly, it's possible to create device specials but kernel won't give a
fsck.  I suggest that symlinks are fine too.

*SKIP*
> I have tried various udev rules, one of which appeared to
> give the desired results with udevadm test, but with an
> actual reboot, nothing changed

Probably, udev rules written in initrd fail to play accordingly.  Or
fail to play at all (and logs are written to syslog what's is missing so
far).

*CUT*

-- 
Torvalds' goal for Linux is very simple: World Domination
Stallman's goal for GNU is even simpler: Freedom

Thread

assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-03-17 19:20 +0000
  Re: assigning specific /dev/videoN to specific USB webcams Robert Heller <heller@deepsoft.com> - 2013-03-17 14:46 -0500
    Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-03-17 20:04 +0000
  Re: assigning specific /dev/videoN to specific USB webcams Kevin Snodgrass <kdsnodgrass@yahoo.com> - 2013-03-24 21:51 +0000
    Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-03-24 22:54 +0000
      Re: assigning specific /dev/videoN to specific USB webcams Robert Heller <heller@deepsoft.com> - 2013-03-24 18:27 -0500
        Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-03-25 02:34 +0000
      Re: assigning specific /dev/videoN to specific USB webcams Kevin Snodgrass <kdsnodgrass@yahoo.com> - 2013-03-31 18:16 +0000
        Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-03-31 19:33 +0000
          Re: assigning specific /dev/videoN to specific USB webcams Kevin Snodgrass <kdsnodgrass@yahoo.com> - 2013-04-11 14:19 +0000
            Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-04-11 15:21 +0000
  Re: assigning specific /dev/videoN to specific USB webcams Eric Pozharski <whynot@pozharski.name> - 2013-04-01 13:52 +0300
    Re: assigning specific /dev/videoN to specific USB webcams J G Miller <miller@yoyo.ORG> - 2013-04-01 18:24 +0000

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