#6670 BLOC 8.2.0 (: Userspace power manager needs to know about the audio device state (was: Userspace (OHM) needs to know about the audio device state)

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#6670: Userspace power manager needs to know about the audio device state
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           Reporter:  cjb        |       Owner:  pgf                 
               Type:  defect     |      Status:  new                 
           Priority:  blocker    |   Milestone:  8.2.0 (was Update.2)
          Component:  kernel     |     Version:                      
         Resolution:             |    Keywords:                      
        Next_action:  never set  |    Verified:  0                   
Deployment_affected:             |   Blockedby:                      
           Blocking:             |  
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Changes (by pgf):

 * cc: AlbertCahalan, dsaxena, dilinger (removed)
 * cc: sascha_silbe (added)
  * owner:  cjb => pgf


Comment:

 inotify is close, but not quite good enough.  turns out data is most often
 transferred to the device via ioctl(), and inotify won't track that.

 it turns out that alsa does offer /proc/asound/card0/pcm0?/sub0/status ,
 which contains a string that corresponds to the device state.  in
 particular "RUNNING" or "DRAINING" tell you that data is being played.

 powerd now uses this, but it exposes issues in activities.   some
 activities (Scratch) send data to the device continuously, long after
 noise is not being made.  this is probably a squeak issue.  others
 (notably the TamTam family, Etoys) send data to the device the entire time
 they're up, whether making noise or not, unless they lose window focus.

-- 
Ticket URL: <http://dev.laptop.org/ticket/6670#comment:8>
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