Re: Not important oops

[James Courtier-Dutton <James@superbug.demon.co.uk>]

Takashi Iwai wrote:
> At Wed, 21 Jan 2004 19:49:39 +0100 (CET),
> Jaroslav wrote:
> 
>>On Wed, 21 Jan 2004, Takashi Iwai wrote:
>>
>>
>>>At Wed, 21 Jan 2004 13:55:53 +0100,
>>>p z oooo wrote:
>>>
>>>>Hi,
>>>>
>>>>When I remove control through hwdep layer on emu10k1 
>>>>driver when in use by oss emulation I got oops. 
>>>>This is because oss emulation holds pointer to this control.
>>>>Is there any api to disable an then enable oss emulation or 
>>>>only proc interface ???
>>>
>>>hmm weird, the access to ctl elements in mixer_oss.c is restricted
>>>with card->controls_rwsem.  since snd_emu10k1_del_controls issues
>>>down_write() for it, it must be safe...
>>
>>I think that he meant that slot->kcontrol members are not removed. 
> 
> 
> ah yes, i overlooked that.
> 
> 
>>We need probably rebuild the OSS mixer -> ALSA control connections when
>>a control - which is used with the OSS mixer code - was removed.
> 
> 
> or, store only the snd_ctl_elem_id instead of kcontrol, and retrieve
> the control at each time.  since the access to the mixer element is
> less frequent than pcm, the overhead by this won't be too much, i
> think.
> 
> but rebuilding would be better, when the mixer elements are completely
> changed and become incompatible with the old setting.
> 
> we can use notify handler for this (e.g. SND_MIXER_OSS_NOTIFY_RECONFIGURE).
> (but the caller should be blocked until the notification is processed,
>  otherwise there would be a race condition.)
> 
> 
> Takashi
> 
While you are looking at the oss emulation mixer, there is another bug 
there.

User application does VOL++.
OSS has a range from 0-100
ALSA uses hardware range of 0-31.
THus: -
OSS VOL=0
OSS VOL++
ALSA VOL stays at 0
OSS READ VOL, = 0;

It seems like to emulate OSS correctly, one needs to hold volume values 
in the OSS mixer emulation code, instead of just passing them through to 
the ALSA mixer.

Cheers
James



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