alsa-lib, dmix, and snd_pcm_open_conf function

alsa-lib, dmix, and snd_pcm_open_conf function

[Simon Tremblay]

Hi, 

I have a problem using dmix on my embedded system (manual installation of
alsa-lib 1.0.15)

When I play a sound with aplay, it works well.

When I try -D dmix or -D plug:dmix parameter, it doesn't work. 

The output is: 

aplay: main:547: audio open error: Operation not permitted

I located my problem in alsa-lib, around line 2154 of alsa-lib/src/pcm/pcm.c: 

err = snd_pcm_open_conf(pcmp, name, root, pcm_conf, stream, mode); (in
snd_pcm_open_noupdate function)

err result is -1 when it's used with dmix...


I don't know how works alsa-lib. I suppose snd_pcm_open_conf has something
related with configuration files... Since I have all default configuration
files... Maybe I must tweak some to be able to use dmix...

Re: alsa-lib, dmix, and snd_pcm_open_conf function

[Simon Tremblay]

Simon Tremblay <bidou <at> videotron.qc.ca> writes:

> I located my problem in alsa-lib, around line 2154 of alsa-lib/src/pcm/pcm.c: 
> 
> err = snd_pcm_open_conf(pcmp, name, root, pcm_conf, stream, mode); (in
> snd_pcm_open_noupdate function)
> 
> err result is -1 when it's used with dmix...
> 


Note that I get 1 for snd_config_search_definition return value.

Re: alsa-lib, dmix, and snd_pcm_open_conf function

[Jaroslav Kysela]

On Mon, 1 Sep 2008, Simon Tremblay wrote:

> Hi, 
> 
> I have a problem using dmix on my embedded system (manual installation of
> alsa-lib 1.0.15)
> 
> When I play a sound with aplay, it works well.
> 
> When I try -D dmix or -D plug:dmix parameter, it doesn't work. 
> 
> The output is: 
> 
> aplay: main:547: audio open error: Operation not permitted

strace will help you. I would look to ipc permissions (alsa.conf):

defaults.pcm.ipc_gid audio
defaults.pcm.ipc_perm 0660

					Jaroslav

-----
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

Re: alsa-lib, dmix, and snd_pcm_open_conf function

[Simon Tremblay]

Jaroslav Kysela a écrit :
> On Mon, 1 Sep 2008, Simon Tremblay wrote:
>
>   
>> Hi, 
>>
>> I have a problem using dmix on my embedded system (manual installation of
>> alsa-lib 1.0.15)
>>
>> When I play a sound with aplay, it works well.
>>
>> When I try -D dmix or -D plug:dmix parameter, it doesn't work. 
>>
>> The output is: 
>>
>> aplay: main:547: audio open error: Operation not permitted
>>     
>
> strace will help you. I would look to ipc permissions (alsa.conf):
>
> defaults.pcm.ipc_gid audio
> defaults.pcm.ipc_perm 066
Thanks, but I just want to know where I manage that for IPC? I created 
an audio group and my /dev/snd/* files are in this group and have 0660 
as permissions.

Simon