[alsa-devel] [PATCH] ALSA - hda: hdmi flag to stop playback when monitor is disconnected

[Takashi Iwai]

On Wed, 11 Nov 2015 15:43:00 +0100,
Yang, Libin wrote:
> 
> 
> > -----Original Message-----
> > From: Yang, Libin
> > Sent: Wednesday, November 11, 2015 10:24 PM
> > To: 'Takashi Iwai'; libin.yang at linux.intel.com
> > Cc: David Henningsson; alsa-devel at alsa-project.org;
> > mengdong.lin at linux.intel.com
> > Subject: RE: [PATCH] ALSA - hda: hdmi flag to stop playback when
> > monitor is disconnected
> > 
> > 
> > > -----Original Message-----
> > > From: Takashi Iwai [mailto:tiwai at suse.de]
> > > Sent: Wednesday, November 11, 2015 10:13 PM
> > > To: libin.yang at linux.intel.com
> > > Cc: David Henningsson; alsa-devel at alsa-project.org;
> > > mengdong.lin at linux.intel.com; Yang, Libin
> > > Subject: Re: [PATCH] ALSA - hda: hdmi flag to stop playback when
> > > monitor is disconnected
> > >
> > > On Wed, 11 Nov 2015 10:02:14 +0100,
> > > Takashi Iwai wrote:
> > > >
> > > > On Wed, 11 Nov 2015 09:39:09 +0100,
> > > > libin.yang at linux.intel.com wrote:
> > > > >
> > > > > From: Libin Yang <libin.yang at linux.intel.com>
> > > > >
> > > > > Add a flag that user can decide to stop HDMI/DP playback when
> > > > > the corresponding monitor is disconnected and refuse to open PCM
> > > > > if there is no monitor connected.
> > > > >
> > > > > Background:
> > > > > When a monitor is disconnected and a new monitor is connected,
> > > > > the parameters of the 2 monitors may be different. Audio driver
> > > > > need handle this situation.
> > > > >
> > > > > Besides, stopping playback when monitor is disconnected will
> > > > > help to save the power.
> > > > >
> > > > > Signed-off-by: Libin Yang <libin.yang at linux.intel.com>
> > > >
> > > > Thanks.  Below are just nitpicking, so let's test this patch at first,
> > > > especially to see whether it has any significant influence on PA, then
> > > > respin with the fixes.
> > > >
> > > > David, care to check in your side, too?
> > >
> > > So I tested this with PA 7.1, and it failed, unfortunately.
> > > In short:
> > > - PA needs the PCM access at probe.  If it gets an error, the device
> > >   will be never enumerated again
> > 
> > Thanks for test.
> > 
> > If so, should we re-write the hdmi_pcm_open() and
> > generic_hdmi_playback_pcm_prepare() function to make
> > the probe works? Or not support dynamic pcm assignment?
> > 
> > > - PA removes the device when it's disconnected.  The PCM stop with
> > >   DISCONNECT state leads to the device disappearance.
> > 
> > If we can't use DISCONNECT, what else can we use? Or we can't
> > stop PCM when monitor is disconnected?
> 
> BTW: I did the test on aplay. But I missed the test on PA.
> Where can I get the PA test cases?

Just use PA on your desktop.  Start PA with and without monitor
plugged.  Play via DP, then unplug, then watch the state change of
PA.


Takashi