[alsa-devel] Bug in setting channels, related to recent ELD/EDID changes?

[Takashi Iwai]

At Tue, 11 Jan 2011 18:58:51 +0200,
Anssi Hannula wrote:
> 
> (restored CC I removed, sorry about that)
> 
> On 11.01.2011 09:15, Takashi Iwai wrote:
> > At Mon, 10 Jan 2011 21:36:10 +0100,
> > Takashi Iwai wrote:
> >>
> >> At Mon, 10 Jan 2011 21:58:26 +0200,
> >> Anssi Hannula wrote:
> >>>
> >>>
> >>> Takashi Iwai kirjoitti:
> >>>> At Sun, 02 Jan 2011 12:16:44 +0200,
> >>>> Anssi Hannula wrote:
> >>>>>
> >>>>> Hi!
> >>>>>
> >>>>> Takashi, it seems the "allow all when not plugged in" behaviour you
> >>>>> implemented in bbbe3390 is not enough to allow applications to open the
> >>>>> device before the output device is ready. Switched-off A/V receivers may
> >>>>> provide the information of the plugged-in television which usually
> >>>>> restricts the max_channels to 2, causing applications to fail opening
> >>>>> the device with more channels when a the A/V receiver is switched off.
> >>>>>
> >>>>> Also, even if the application can gracefully fallback to stereo, AFAIK
> >>>>> there is no method for an application to get informed when the
> >>>>> limitation is lifted, so it can't automatically resume multichannel
> >>>>> output when the A/V receiver is switched on again.
> >>>>>
> >>>>> Based on this info, I guess the restrictions based on ELD should be
> >>>>> removed :/
> >>>>> Unless you have some other ideas to fix the issue, of course.
> >>>>
> >>>> What about the patch below?  If it's unplugged, the valid flag should
> >>>> be cleared, so the next open fall backs to the default state (i.e.
> >>>> allows all).
> >>>
> >>> But it is not unplugged. The multichannel-capable receiver forwards EDID
> >>> of TV which doesn't allow more than 2 channels, when the receiver is
> >>> swtiched off.
> >>
> >> Well, in that case, this is the correct behavior, IMO.  At this
> >> moment, setting channels to 2 is the right thing.  Then, how can you
> >> know that more channels will be available in future at all?
> >>
> >> What you want to have a static configuration way by ignoring the ELD
> >> information.  But, the interface isn't pretty easy if it's implemented
> >> in control API, I suppose.
> > 
> > ... or, maybe an easier option is to use the module parameter like
> > the patch below.  It can be changed dynamically via sysfs as well.
> 
> Better than nothing I guess.
> 
> Note that the condition is backwards in the below patch :)

Oh yeah.  I applied the fixed patch to sound git tree now.


thanks,

Takashi