[alsa-devel] [RFC] Fix for conflict of HDMI and SPDIF IEC958 controls

[Takashi Iwai]

At Mon, 15 Oct 2012 16:15:20 +0800,
Raymond Yau wrote:
> 
> 2012-10-15 下午3:46 於 "Takashi Iwai" <tiwai at suse.de> 寫道：
> >
> > At Mon, 15 Oct 2012 10:31:50 +0800,
> > Raymond Yau wrote:
> > >
> > > 2012-10-12 下午11:19 於 "Takashi Iwai" <tiwai at suse.de> 寫道：
> > > >
> > > > Hi,
> > > >
> > > > there is a long-standing problem in HD-audio regarding IEC958
> > > > controls.  When both an SPDIF and an HDMI are created on the same
> > > > card (e.g. one from analog codec and one from graphics chip), the
> > > > driver assigns the IEC958 controls just with new indices, 0, 1, 2...
> > > >
> > > > The problem is that there is no way to connect between this index and
> > > > the actual PCM device.  Currently, alsa-lib HDA-Intel.conf has a fixed
> > > > configuration:
> > > >   spdif  -> IEC958 xxx index=0, PCM dev=1
> > > >   hdmi,0 -> IEC958 xxx index=0, PCM dev=3
> > > >   hdmi,1 -> IEC958 xxx index=1, PCM dev=7
> > > >   hdmi,2 -> IEC958 xxx index=2, PCM dev=8
> > > >   hdmi,3 -> IEC958 xxx index=3, PCM dev=9
> > > >
> > > > So obviously spdif and the first hdmi conflict.
> > > >
> > > > Basically this can be fixed by reassigning each IEC958 control with
> > > > the same device number corresponding to the PCM device.  That is, for
> > > > SPDIF, assign a control element with device=1, for HDMI,
> > > > device=3,7...
> > > > However, this obviously breaks the old configuration unless user
> > > > upgrades the alsa-lib configuration.  Thus this is no-go.
> > > >
> > > > Now here is a compromise: the IEC958 control for SPDIF is reassigned
> > > > to device=1 *only* when SPDIF and HDMI coexist.  Since the
> > > > configuration is anyway broken as is now in such a case, it's no big
> > > > deal to fix one side in an incompatible way.  (The reason why SPDIF
> > > > is re-assigned is that I guess majority of user require more HDMI than
> > > > SPDIF in such a configuration.)
> > > >
> > > > In addition, we need a fix in alsa-lib.  Also not for breaking the
> > > > compatibility with older kernel, we need some fallback check.  I did a
> > > > quick hack to alsa-lib conf code and added "skip_rest" option to the
> > > > hook element, so that only the first matching element is taken.
> > >
> > > how about those hdmi jack and iec958 on ad1989b?
> >
> > On AD codecs, all digital outputs are exposed as a single cloned
> > device with HDA_PCM_TYPE_SPDIF.
> 
> how about ad1988b with nvidia codec ?

Nvidia codec provides devices only with HDA_PCM_TYPE_HDMI, of course.

> from user point of view , how can they differenitate hdmi jack is digital
> ouput and hdmi output ?

The device 1 is from AD and the device 3 is from Nvidia codec, as you
can see below.  And this is exactly the case the conflict happens as I
mentioned in the original mail.

Which is connected to what output, you can't know exactly unless you
compare the obtained ELD.  The HD-audio spec isn't good enough to
identify the actual output.


Takashi


> https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/881826
> 
> **** List of PLAYBACK Hardware Devices ****
> card 0: NVidia [HDA NVidia], device 0: AD198x Analog [AD198x Analog]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
> card 0: NVidia [HDA NVidia], device 1: AD198x Digital [AD198x Digital]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
> card 0: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0