I just thought I would share something I found out about alsa & udev.

I, along with a few others I suspect, was wondering where /dev/dsp and friends had got to when running udev on kernel 2.6.*

I have a SBlive soundcard and compile ALSA separately from the kernel.

All was fine until udev. udev is still at a fairly beta stage on Slackware I think, and although some ALSA stuff appeared in /dev/snd, there was a fair bit missing.
I think most of it is really for OSS compatibility, but this is important to some people, at least in kde.

First thing I tried was running the alsa snddevices script from rc.local. It worked, but seemed untidy.

From the Gentoo forums I discovered a post by Decibels, who wrote an initscript to load the missing devices into /dev. I modified this to go straight into /etc/udev/scripts/make_extra_nodes.sh. Notice /dev/snd is created. Although this dir was being created, it was too late (presumably because the alsa module is loaded later than the kernel built-in stuff) I also changed the permissions to something fairly lax, so be aware of this if you use it:

________________________________________________________________________

mkdir $udev_root/snd

# load some missing sound stuff:
mknod -m 666 /dev/snd/controlC0 c 116 0
mknod -m 666 /dev/snd/hwC0D0 c 116 4
mknod -m 666 /dev/snd/hwC0D1 c 116 5
mknod -m 666 /dev/snd/hwC0D2 c 116 6
mknod -m 666 /dev/snd/hwC0D3 c 116 7
mknod -m 666 /dev/snd/midiC0D0 c 116 8
mknod -m 666 /dev/snd/midiC0D1 c 116 9
mknod -m 666 /dev/snd/midiC0D2 c 116 10
mknod -m 666 /dev/snd/midiC0D3 c 116 11
mknod -m 666 /dev/snd/midiC0D4 c 116 12
mknod -m 666 /dev/snd/midiC0D5 c 116 13
mknod -m 666 /dev/snd/midiC0D6 c 116 14
mknod -m 666 /dev/snd/midiC0D7 c 116 15
mknod -m 666 /dev/snd/pcmC0D0c c 116 24
mknod -m 666 /dev/snd/pcmC0D0p c 116 16
mknod -m 666 /dev/snd/pcmC0D1c c 116 25
mknod -m 666 /dev/snd/pcmC0D1p c 116 17
mknod -m 666 /dev/snd/pcmC0D2c c 116 26
mknod -m 666 /dev/snd/pcmC0D2p c 116 18
mknod -m 666 /dev/snd/pcmC0D3p c 116 19
mknod -m 666 /dev/snd/pcmC0D3c c 116 27
mknod -m 666 /dev/snd/pcmC0D4c c 116 28
mknod -m 666 /dev/snd/pcmC0D4p c 116 20
mknod -m 666 /dev/snd/pcmC0D5c c 116 29
mknod -m 666 /dev/snd/pcmC0D5p c 116 21
mknod -m 666 /dev/snd/pcmC0D6c c 116 30
mknod -m 666 /dev/snd/pcmC0D6p c 116 22
mknod -m 666 /dev/snd/pcmC0D7c c 116 31
mknod -m 666 /dev/snd/pcmC0D7p c 116 23
mknod -m 666 /dev/snd/seq c 116 1
mknod -m 666 /dev/snd/timer c 116 33
chown root:audio /dev/snd/*
mknod -m 666 /dev/admmidi0 c 14 14
mknod -m 666 /dev/admmidi1 c 14 30
mknod -m 666 /dev/admmidi2 c 14 46
mknod -m 666 /dev/admmidi3 c 14 62
chown root:audio /dev/admmidi*
mknod -m 666 /dev/adsp0 c 14 12
mknod -m 666 /dev/adsp1 c 14 28
mknod -m 666 /dev/adsp2 c 14 44
mknod -m 666 /dev/adsp3 c 14 60
chown root:audio /dev/adsp*
mknod -m 666 /dev/amidi0 c 14 13
mknod -m 666 /dev/amidi1 c 14 29
mknod -m 666 /dev/amidi2 c 14 45
mknod -m 666 /dev/amidi3 c 14 61
chown root:audio /dev/amidi*
mknod -m 666 /dev/amixer0 c 14 11
mknod -m 666 /dev/amixer1 c 14 27
mknod -m 666 /dev/amixer2 c 14 43
mknod -m 666 /dev/amixer3 c 14 59
chown root:audio /dev/amixer*
mknod -m 666 /dev/dmfm0 c 14 10
mknod -m 666 /dev/dmfm1 c 14 26
mknod -m 666 /dev/dmfm2 c 14 42
mknod -m 666 /dev/dmfm3 c 14 58
chown root:audio /dev/dmfm*
mknod -m 666 /dev/dmmidi0 c 14 9
mknod -m 666 /dev/dmmidi1 c 14 25
mknod -m 666 /dev/dmmidi2 c 14 41
mknod -m 666 /dev/dmmidi3 c 14 57
chown root:audio /dev/dmmidi*
mknod -m 666 /dev/mixer0 c 14 0
mknod -m 666 /dev/mixer1 c 14 16
mknod -m 666 /dev/mixer2 c 14 32
mknod -m 666 /dev/mixer3 c 14 48
chown root:audio /dev/mixer*
mknod -m 666 /dev/music c 14 8
chown root:audio /dev/music

ln -s /dev/adsp0 /dev/adsp
ln -s /dev/amidi0 /dev/amidi
ln -s /dev/midi0 /dev/midi
ln -s /dev/music /dev/sequencer2

______________________________________________________________________


if you are interested in using this, first back up the original.
Then read /dev and see what is already there, and remove from the above list
then paste into the file make_extra_nodes.sh.
You may also want to review the permissions in /etc/udev/permissions.d/udev.permissions.

I hope that was at least food for thought for someone - it took me 20mins to write!

tobyl

Would it not be simpler to build what you need into the kernel?

Most of this stuff is already provided by the new udev package, here is what I get without modif :

$ ls -al /dev/* | grep audio
lrwxrwxrwx 1 root root 11 2004-07-05 11:35 /dev/audio -> sound/audio
crw-rw--w- 1 root audio 14, 9 2004-07-05 11:35 /dev/dmmidi
crw-rw--w- 1 root audio 14, 2 2004-07-05 11:35 /dev/midi
crw-rw-rw- 1 root audio 116, 0 2004-07-05 13:34 controlC0
crw-rw--w- 1 root audio 116, 4 2004-07-05 11:35 hwC0D0
crw-rw-rw- 1 root audio 116, 8 2004-07-05 11:35 midiC0D0
crw-rw--w- 1 root audio 116, 24 2004-07-05 11:35 pcmC0D0c
crw-rw-rw- 1 root audio 116, 16 2004-07-05 11:35 pcmC0D0p
crw-rw--w- 1 root audio 116, 25 2004-07-05 11:35 pcmC0D1c
crw-rw--w- 1 root audio 116, 26 2004-07-05 11:35 pcmC0D2c
crw-rw-rw- 1 root audio 116, 19 2004-07-05 11:35 pcmC0D3p
crw-rw-rw- 1 root audio 116, 33 2004-07-05 11:35 timer
crw-rw--w- 1 root audio 14, 12 2004-07-05 11:35 adsp
crw-rw--w- 1 root audio 14, 4 2004-07-05 11:35 audio
crw-rw--w- 1 root audio 14, 3 2004-07-05 11:35 dsp
crw-rw--w- 1 root audio 14, 0 2004-07-05 11:35 mixer
$

/sbin/udevstart should take care of this as well.

Udev should work fine as long as you have hotplug enabled, as well -- the two work together to create the /dev nodes you need.

--Shade

Thanks for your comments
Andrew: yes this is a fair comment. Up until now I have tried to keep things modular, and Slackware is designed to use alsa as a module. Also due to various problems with sound in the past I have found compiling my own alsa to be the most successful.

Keefaz & Shade: I went to all this trouble precisely because I was not getting the correct entries in /dev. Yes, I have hotplug and udev, the most recent versions.
I did get some stuff like keefaz but with several omissions, including /dev/dsp and /dev/mixer. (actually I missed /dev/dsp and /dev/dsp > /dev/dsp0 in my first post)

I am now wondering whether something else is amiss for these entries to be missed by udev. Still, it is working now.

I ran into the problem when I disabled hotplug on my laptop... Didn't have the problem before.

Running udevstart and re-enabling hotplug corrected the problems, though -- Just sharing my experience

I need to read up some more on dynamic device creation -- what hotplug's role is with udev -- that sort of thing.

--Shade

Exact same situation here... disabled hotplug and devices disappeared... turned it back on and sound worked again...

This is from my post here.