[alsa-devel] [PATCH] Show processing coefficients in codec proc file

[Takashi Iwai]

At Fri, 20 Aug 2010 16:46:25 +0200,
David Henningsson wrote:
> 
> 2010-08-19 22:24, Takashi Iwai skrev:
> > At Thu, 19 Aug 2010 20:48:56 +0200,
> > David Henningsson wrote:
> >>
> >> 2010-08-19 20:28, Takashi Iwai skrev:
> >>> At Thu, 19 Aug 2010 20:17:42 +0200,
> >>> David Henningsson wrote:
> >>>>
> >>>> This patch is helpful for tracking down bugs without having all
> >>>> information about the chip.
> >>>
> >>> I don't want to change coef index in reading a proc file in general.
> >>
> >> Good point. But I think the solution to that problem would be to
> >> - read current index
> >> - do the loop
> >> - restore current index
> >>
> >> ...and perhaps protect that with an appropriate mutex (which one)?
> >>
> >>> If any, you should implement a codec-specific hook.
> >>
> >> I'm sorry, but I don't really see how that would help...?
> > 
> > If it's specific to a codec, then you know whether reading the coef
> > in that way can be harmful or not.  It's not only about the race
> > via proc file but also the influence of coef on the actual codec
> > behavior.
> 
> Oh, so there are chips that are *that* broken...
> 
> Yet it could be a lifesaver so I wouldn't want to give up on the idea
> just yet...

As mentioned, I don't mind to add it but as a beginning, let's add it
conditionally for known-working codecs.  Eventually we can put it to
the generic part, with a blacklisting if needed.

> Do you know off the top of your head approximately what codec chips this
> is about, where reading a coef (or setting its index) can cause unwanted
> side-effects?

I don't remember exactly which one.  I thought either an old Realtek
or AD codec.


Takashi