Hi all,
I have a C-Media USB Headphone Set which is working well. One issue though is
that when plugging it in the mixer levels are initialized to bad values. The
"Speaker" level is set to 100% (*very* loud, like in "ouch !!!") while the "Mic
Capture" level is set to 0%.
Therefore I set the mixer levels by hand (using alsamixer) until now. So I wrote
a script which is invoked by udev. The script tries to set the levels using amixer.
dmesg output:
================================================================================
[ 6010.971400] usb 5-1: new full speed USB device using uhci_hcd and address 2
[ 6011.116126] usb 5-1: configuration #1 chosen from 1 choice
[ 6011.124401] input: C-Media USB Headphone Set as
/devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1:1.3/input/input9
[ 6011.127448] generic-usb 0003:0D8C:000C.0002: input: USB HID v1.00 Device
[C-Media USB Headphone Set ] on usb-0000:00:1d.0-1/input3
[ 6011.127931] usb 5-1: New USB device found, idVendor=0d8c, idProduct=000c
[ 6011.127936] usb 5-1: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[ 6011.127942] usb 5-1: Product: C-Media USB Headphone Set
[ 6011.309124] usbcore: registered new interface driver snd-usb-audio
================================================================================
amixer output:
================================================================================
jens:~> amixer -c1
Simple mixer control 'Mic',0
Capabilities: pvolume pvolume-joined cvolume cvolume-joined pswitch
pswitch-joined cswitch cswitch-joined
Playback channels: Mono
Capture channels: Mono
Limits: Playback 0 - 32 Capture 0 - 16
Mono: Playback 23 [72%] [34.50dB] [off] Capture 0 [0%] [0.00dB] [on]
Simple mixer control 'Auto Gain Control',0
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Simple mixer control 'Speaker',0
Capabilities: pvolume pswitch pswitch-joined
Playback channels: Front Left - Front Right
Limits: Playback 0 - 151
Mono:
Front Left: Playback 150 [99%] [-1.37dB] [on]
Front Right: Playback 150 [99%] [-1.37dB] [on]
================================================================================
So I wrote the following script and udev rule:
Udev rule (a single line in the file):
================ /etc/udev/rules.d/usb-headset.rules contents: =================
ATTR{idProduct}=="000c", ATTR{idVendor}=="0d8c", ACTION=="add",
RUN+="/usr/local/bin/headset_volume.sh"
================================================================================
Script (It writes the amixer output to a logfile for debugging purposes):
================ /usr/local/bin/headset_volume.sh contents: ====================
#!/bin/sh
exec >> /home/jens/log.file
/usr/bin/amixer -c1 sset Mic 75%
echo $?
/usr/bin/amixer -c1 sset Speaker 25%
echo $?
================================================================================
The script is executed since I get the log file, but amixer obviously isn't
executed correctly, here's the log file contents:
============================ logfile contents ================================
Usage: amixer <options> [command]
Available options:
-h,--help this help
-c,--card N select the card
-D,--device N select the device, default 'default'
-d,--debug debug mode
-n,--nocheck do not perform range checking
-v,--version print version of this program
-q,--quiet be quiet
-i,--inactive show also inactive controls
-a,--abstract L select abstraction level (none or basic)
-s,--stdin Read and execute commands from stdin sequentially
Available commands:
scontrols show all mixer simple controls
scontents show contents of all mixer simple controls (default command)
sset sID P set contents for one mixer simple control
sget sID get contents for one mixer simple control
controls show all controls for given card
contents show contents of all controls for given card
cset cID P set control contents for one control
cget cID get control contents for one control
1
Usage: amixer <options> [command]
Available options:
-h,--help this help
-c,--card N select the card
-D,--device N select the device, default 'default'
-d,--debug debug mode
-n,--nocheck do not perform range checking
-v,--version print version of this program
-q,--quiet be quiet
-i,--inactive show also inactive controls
-a,--abstract L select abstraction level (none or basic)
-s,--stdin Read and execute commands from stdin sequentially
Available commands:
scontrols show all mixer simple controls
scontents show contents of all mixer simple controls (default command)
sset sID P set contents for one mixer simple control
sget sID get contents for one mixer simple control
controls show all controls for given card
contents show contents of all controls for given card
cset cID P set control contents for one control
cget cID get control contents for one control
1
============================ end of logfile ================================
Of course, if I manually execute the commands from the script they work
flawlessly. Also executing the script manually from a terminal sets the volume
levels correctly.
Adding a "sleep 5" at the top of the script didn't work either.
I also tried manually invoking amixer with a clean environment (since udev only
passes a very minimalistic environment to the script) but amixer worked without
problems.
What am I missing ? Why is amixer not working correctly when it is called from udev.
Best regards,
Jens
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