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Re: How to set group of video and audio devices automatically

Derek Tattersall wrote:
Mikkel L. Ellertson wrote:
Derek Tattersall wrote:

think I have the multiple sound cards more or less sorted out.

To sum up what I did, In order to get the 2 sound cards working for different users, I had to modify 4 different configuration files on my machine. They were:


I found that adding this to
/etc/security/console.perms.d/50-default.perms works:

<audio>=/dev/snd/* /dev/mixer* /dev/dsp*

<console>  0660 <video>      0660 root.pulse
<console>  0660 <audio>      0660 root.pulse

Then add any users who might want to use those devices to the pulse group

Unfortunately  this only applies to devices that are plugged in on boot
up. Are devices that are plugged in after boot up handled by udev?

It tuns out that if I write my udev rules correctly (no typos) it does work the way I want it to.

udev rules:

# Webcam
SYSFS{idVendor}=="046d", SYSFS{idProduct}=="0990", MODE="660", GROUP="pulse"
# Usb audio card
SYSFS{idVendor}=="0c45", SYSFS{idProduct}=="1677", MODE="660", GROUP="pulse"

modules.conf entries:

# On board audio card
alias snd-card-0 snd-hda-intel
# HDTV tuner card
alias snd-card-1 cx88_alsa
# USB Audio card
alias snd-card-2 snd-usb-audio
# Webcam microphone
alias snd-card-3 snd-usb-audio

options snd-hda-intel index=0
options cx88_alsa index=1
options snd-usb-audio index=2,3 vid=0x0c45,0x46d pid=0x1677,0x990

My local .asoundrc file. This sets up the default card for the console user. The mythtv user will set the Intel card to be default.

pcm.Intel { type hw; card Intel; }
ctl.Intel { type hw; card Intel; }
pcm.CX8801 { type hw; card CX8801; }
ctl.CX8801 { type hw; card CX8801; }
pcm.Audio { type hw; card Audio; }
ctl.Audio { type hw; card Audio; }
pcm.U0x46d0x990 { type hw; card U0x46d0x990; }
ctl.U0x46d0x990 { type hw; card U0x46d0x990; }
pcm.!default pcm.Audio
ctl.!default ctl.Audio

So after I modified /etc/security/console.perms.d/50-default.perms , /etc/udev/rules.d/90-alsa.rules, /etc/modprobe.d/modprobe.conf.dist, and my local .asoundrc it all just works.

Have you tried it? I have not looked lately, but I know that udev
used to call console.perms when a device was hotplugged, so it could
set permissions if necessary.

Yes I did try it. When the device was plugged into the USB port on boot up, the permissions were set as I wanted them to be.

When the device (A USB audio card) was plugged in after boot up, the permissions were not set properly.

I may have to mess with the udev rules further. Maybe if I write some kind of post-install script that manually sets the permissions.

Derek Tattersall

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