[alsa-devel] PROC_COEF/PROC_INDEX question

[Takashi Iwai]

At Fri, 7 Aug 2009 18:01:21 +0800,
Wu Fengguang wrote:
> 
> On Fri, Aug 07, 2009 at 05:45:14PM +0800, Takashi Iwai wrote:
> > At Fri, 7 Aug 2009 17:38:59 +0800,
> > Wu Fengguang wrote:
> > > 
> > > Hello,
> > > 
> > > I'm not sure of the usage for GET_PROC_COEF/GET_COEF_INDEX, and found
> > > that their return value is unstable (changing all the time) for codec:
> > > 
> > >         Codec: Realtek ALC888
> > >         Address: 2
> > >         Function Id: 0x1
> > >         Vendor Id: 0x10ec0888
> > >         Subsystem Id: 0x80860023
> > >         Revision Id: 0x100202
> > > 
> > > For example:
> > > 
> > > # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0 
> > > nid = 0x20, verb = 0xc00, param = 0x0
> > > value = 0x80
> > > # hda-verb /dev/snd/hwC0D2 0x20 GET_COEF_INDEX 0
> > > nid = 0x20, verb = 0xd00, param = 0x0
> > > value = 0xe
> > > # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0 
> > > nid = 0x20, verb = 0xc00, param = 0x0
> > > value = 0x9c00
> > > # hda-verb /dev/snd/hwC0D2 0x20 GET_COEF_INDEX 0
> > > nid = 0x20, verb = 0xd00, param = 0x0
> > > value = 0xf
> > > 
> > > I wonder if this is the normal case?
> > 
> > AFAIK, depending on the mode, the index is incremented automatically.
> 
> Ah, yes. That's in line with the above data.
> 
> When repeatingly call  GET_PROC_COEF, it returns some 'random' values:
> 
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0
>         nid = 0x20, verb = 0xc00, param = 0x0
>         value = 0x4f
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0
>         nid = 0x20, verb = 0xc00, param = 0x0
>         value = 0x8000
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0
>         nid = 0x20, verb = 0xc00, param = 0x0
>         value = 0x2520
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_PROC_COEF 0
>         nid = 0x20, verb = 0xc00, param = 0x0
>         value = 0x3e00

I guess it's not random but just the value of the next index.

> But when repeatingly call GET_COEF_INDEX, it returns the same value:
> 
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_COEF_INDEX 0
>         nid = 0x20, verb = 0xd00, param = 0x0
>         value = 0xd
>         # hda-verb /dev/snd/hwC0D2 0x20 GET_COEF_INDEX 0
>         nid = 0x20, verb = 0xd00, param = 0x0
>         value = 0xd

Reading the index itself doesn't increment the index.  Reading
the coef value increases the index.  So is my understanding.


Takashi