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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