alsa-oss emulation bug?

alsa-oss emulation bug?

[Roderick Colenbrander]

Hi,

At the moment I'm debugging an alsa-oss emulation related bug. I'm using 
alsa .9.8 on a i810 card. Using native alsa code I can query the capabilities 
of the card. Alsa tells that only some 16bit formats are supported which is 
is correct. When I'm in oss emulation mode, the driver also advertises 
various 8bit formats which is wrong. Because of this problem the app I'm 
debugging (Wine) is crashing as it tries to use 8bit while it isn't 
supported.

After some digging in the alsa oss source I found this in 
snd_pcm_oss_get_formats of pcm_oss.c:
        if ((err = snd_pcm_oss_get_active_substream(pcm_oss_file, &substream)) 
< 0)
                return err;
        if (atomic_read(&substream->runtime->mmap_count)) {
                direct = 1;
        } else {
                snd_pcm_oss_setup_t *setup = substream->oss.setup;
                direct = (setup != NULL && setup->direct);
        }
        if (!direct)
                return AFMT_MU_LAW | AFMT_U8 |
                       AFMT_S16_LE | AFMT_S16_BE |
                       AFMT_S8 | AFMT_U16_LE |
                       AFMT_U16_BE;

The supported formats alsa returns in my case is what you see behind the 
if(!direct) line, so for some reason direct = 0. As I barely know anything 
about alsa I hope you guys can help me out.

Thanks in advance,
Roderick Colenbrander



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Re: alsa-oss emulation bug?

[Takashi Iwai]

At Mon, 17 Nov 2003 23:02:04 +0100,
Roderick Colenbrander wrote:
> 
> Hi,
> 
> At the moment I'm debugging an alsa-oss emulation related bug. I'm using 
> alsa .9.8 on a i810 card. Using native alsa code I can query the capabilities 
> of the card. Alsa tells that only some 16bit formats are supported which is 
> is correct. When I'm in oss emulation mode, the driver also advertises 
> various 8bit formats which is wrong. Because of this problem the app I'm 
> debugging (Wine) is crashing as it tries to use 8bit while it isn't 
> supported.
> 
> After some digging in the alsa oss source I found this in 
> snd_pcm_oss_get_formats of pcm_oss.c:
>         if ((err = snd_pcm_oss_get_active_substream(pcm_oss_file, &substream)) 
> < 0)
>                 return err;
>         if (atomic_read(&substream->runtime->mmap_count)) {
>                 direct = 1;
>         } else {
>                 snd_pcm_oss_setup_t *setup = substream->oss.setup;
>                 direct = (setup != NULL && setup->direct);
>         }
>         if (!direct)
>                 return AFMT_MU_LAW | AFMT_U8 |
>                        AFMT_S16_LE | AFMT_S16_BE |
>                        AFMT_S8 | AFMT_U16_LE |
>                        AFMT_U16_BE;
> 
> The supported formats alsa returns in my case is what you see behind the 
> if(!direct) line, so for some reason direct = 0. As I barely know anything 
> about alsa I hope you guys can help me out.

see alsa-kernel/Documentation/OSS-Emulation.txt, section "PCM mode".
the default (plugin) mode is sometimes problematic when mmap is used.


Takashi


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