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Groups > comp.os.linux.misc > #7710

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

From J G Miller <miller@yoyo.ORG>
Newsgroups comp.os.linux.misc
Subject Re: assigning specific /dev/videoN to specific USB webcams
Date 2013-03-31 19:33 +0000
Organization A noiseless patient Spider
Message-ID <kja32b$olk$1@dont-email.me> (permalink)
References <ki552n$nat$1@dont-email.me> <kinsh3$2ua$2@dont-email.me> <kio081$ui1$2@dont-email.me> <kj9ui3$7pp$1@dont-email.me>

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On Sunday, March 31st, 2013, at 18:16:36h +0000, Kevin Snodgrass wrote:

> ok, but WHY does V4L assign analog devices /dev/videoX and digital /dev/
> dvb/adapterX ?

As I tried to explain/second guess, back in the days of the analog devices,
the developers only recognized one "capability/feature" on the card and
so that was /dev/videoN.

For digital cards, these have more than one "capability/feature"
and so require a directory to keep the device interface files
together.

It is similar to the way there was a change for audio in device interface
files in going from OSS to ALSA.

Under OSS, an audio card has /dev/dspN and /dev/mixerN and maybe
/dev/sequencerN.  Now under ALSA, everything is kept
together under /dev/snd.

They should have used a similar scheme to v4l2 of /dev/snd/card0,
/dev/snd/card1 as for DVB cards, but as you so correctly observed
there is a more or less a total lack of consist*e*ncy between
different kernel modules, and I suppose, ultimately the blame
for that can be laid at the foot of Linus Torvalds, who will probably
respond that he could care less about such issues.

There seems to be a general attitude of "so long as it works"
(sort of anyways), that is good enough, so stop asking awkward
questions.

Maybe they do things more logically and consistently in BSD
with their benevolent dictatorship style of management, rather
than the Linux laissez-faire approach?

Anyways I am still awaiting (probably in vain) for some
help with udev rules, since obviously this is the wrong group
in which to post such a technical question.

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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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