#8006 HIGH 8.2.0 (: joyride-2301: backlight switches off for no good reason

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#8006: joyride-2301:  backlight switches off for no good reason
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   Reporter:  thomaswamm           |       Owner:  cjb                                               
       Type:  defect               |      Status:  new                                               
   Priority:  high                 |   Milestone:  8.2.0 (was Update.2)                              
  Component:  power manager (OHM)  |     Version:  Development build as of this date                 
 Resolution:                       |    Keywords:  power_manager blocks-:8.2.0 polish:8.2.0 cjbfor8.2
Next_action:  diagnose             |    Verified:  0                                                 
  Blockedby:                       |    Blocking:                                                    
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Changes (by gnu):

 * cc: gnu (added)


Comment:

 While I was doing power testing (http://wiki.laptop.org/go/XO_Power_Draw)
 tonight, I too ran across this bug in 8.2-759.  It's truly annoying,
 mostly because when it hits you, it keeps hitting you over and over.
 Pressing normal keys doesn't fix it, the way a screen saver should; and
 brightening the screen with the brightness keys only fixes it temporarily,
 until it hits you again.

 I was about to file a bug report on it -- then I found this well-
 characterized bug.  Thanks Thomas!

 The bug seems to only appear after you press the "dim" key at least once
 since rebooting.

 An easier end-user circumvention, when it appears, may be to crash and
 restart X (ctrl-alt-erase).  I have not tried this, but if we're going to
 relnote it, I recommend seeing
 if this works; it's less intrusive than typing sudo commands, or rebooting
 the whole machine.

 Hmm!  If something is reading out the brightness setting ONLY WHEN THE
 20-minute DPMS TIMER GOES OFF, and then setting the brightness to that
 value ON THE 1-minute OHM TIMER, no wonder it can't be fixed by normal
 user actions.  Whenever the 20-minute DPMS timer goes off, the 1-minute
 Ohm timer will have first set the brightness to the bad value, so it will
 re-get the bad value 19 minutes later.  The miracle is that it works at
 all, before you dim anything.

 Since we have a perfectly good X screen saver, I wonder why ohm is getting
 involved at all.  Perhaps the problem is that the X screen saver doesn't
 allow dimming -- only blanking the screen, or DPMS off (blanking at a
 deeper level).  Currently the DCON X driver treats all DPMS states other
 than "on" alike: the screen goes off.  If we changed the X driver so that
 "dpms standby" gave a dim or monochrome screen image, and "dpms suspend"
 or "dpms off" turned off the whole screen, perhaps we could rip this stuff
 permanently out of ohm?

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Ticket URL: <http://dev.laptop.org/ticket/8006#comment:34>
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