Detecting ALSA OSS emulation

Detecting ALSA OSS emulation

[Glenn Maynard]

Is there a reliable way to find out if /dev/dsp is being handled by
ALSA?  I want to be able to detect this for diagnostics.  (If /dev/dsp
is ALSA, the native alsa-lib code should have been used, and something
has gone wrong.)  Currently, I'm checking for the existance of
/proc/asound/version, but at least one user had a configuration where
that file existed but /dev/dsp was really OSS.

(That's what it looked like, and what he claimed, at least; I havn't
tried to reproduce that configuration, with both ALSA and OSS loaded
and only OSS actually handling sound.  It's possible something else
was happening and the user was wrong.)

-- 
Glenn Maynard


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RE: Detecting ALSA OSS emulation

[p z oooo]

Hi,

Probably user has normal soundcard handled by ALSA and TV card 
(btaudio or saa7134) which provides only OSS drivers (warning - only 
recording - not playback). TV card is default /dev/dsp (can by 
changed by module option for btaudio, saa7134). For BT87x users there 
is alsa driver in ALSA 1.0.0rc2 for saa7134 not.

Peter Zubaj



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Re: Detecting ALSA OSS emulation

[Glenn Maynard]

On Mon, Dec 08, 2003 at 01:15:18PM +0100, p z oooo wrote:
> Probably user has normal soundcard handled by ALSA and TV card
> (btaudio or saa7134) which provides only OSS drivers (warning - only
> recording - not playback). TV card is default /dev/dsp (can by
> changed by module option for btaudio, saa7134). For BT87x users there
> is alsa driver in ALSA 1.0.0rc2 for saa7134 not.

Err, no, this user's configuration didn't have a working ALSA at all.
dsnd_pcm_open returned ENOENT.  His other applications were likely all
using /dev/dsp, too.  However, since /proc/asound/version existed,
my code figured that ALSA was loaded and complained ("/dev/dsp? why
isn't ALSA being used?")

-- 
Glenn Maynard


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Re: Detecting ALSA OSS emulation

[Jaroslav Kysela]

On Mon, 8 Dec 2003, Glenn Maynard wrote:

> Is there a reliable way to find out if /dev/dsp is being handled by
> ALSA?  I want to be able to detect this for diagnostics.  (If /dev/dsp
> is ALSA, the native alsa-lib code should have been used, and something
> has gone wrong.)  Currently, I'm checking for the existance of
> /proc/asound/version, but at least one user had a configuration where
> that file existed but /dev/dsp was really OSS.
> 
> (That's what it looked like, and what he claimed, at least; I havn't
> tried to reproduce that configuration, with both ALSA and OSS loaded
> and only OSS actually handling sound.  It's possible something else
> was happening and the user was wrong.)

We use this OSS version:

#define SNDRV_OSS_VERSION         ((3<<16)|(8<<8)|(1<<4)|(0))   /* 3.8.1a */

Ok, I've just added a new ioctl for more easy and reliable checks for 
mixer and pcm emulation:

#define OSS_ALSAEMULVER         _SIOR ('M', 249, int)

This ioctl will return 1 as integer:

int ver;
if (ioctl(fd, OSS_ALSAEMULVER, &ver) == 0 && ver > 0)
	printf("fd is ALSA's emulation handle\n");

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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