#10210 NORM 1.5-sof: Make SISUSBVGA devices trivial to use

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#10210: Make SISUSBVGA devices trivial to use
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 Reporter:  martin.langhoff  |                 Owner:                     
     Type:  enhancement      |                Status:  new                
 Priority:  normal           |             Milestone:  1.5-software-update
Component:  olpc-utils       |               Version:  not specified      
 Keywords:                   |           Next_action:  never set          
 Verified:  0                |   Deployment_affected:                     
Blockedby:                   |              Blocking:                     
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 After exploring various techniques, I have a winner using Xinerama +
 Xephyr.

 This patch to olpc-utils, plus a dependency on xorg-x11-drv-sisvga makes
 it Just Work.

 All the components of the patch attached have been tested, except the SPEC
 file changes.

 To use

  - Plug the SISUSB2VGA device

  - Reboot & Enjoy

 Limitations and notes:

   - Needs to be "switched on" at X startup time. olpc-configure checks at
 boot time if sisusbvga is loaded and changes the xorg.conf symlink if
 needed. My patch also fixes a longstanding old bug where the xorg.conf was
 'set' in the first boot.

   - The desktop is 1024x768 on both screens. On the XO, the desktop
 appears in the top-left corner -- on the external monitor / projector it
 fills up the screen perfectly.

   - Icons can appear slightly pixellated. I think this technique may
 expose a bug in Sugar and in some activities (ie: TurtleArt) that keep a
 copy of rendered SVGs as bitmaps.

   - Performance is slow but acceptable. The SiSUSB driver is not
 accelerated, and we are saturating the USB 2 bandwidth with the amount of
 pixels and the bitdepth.

  - The Sugar cursor works, thanks to Xephyr (it doesn't with most of the
 other techniques, including pure Xinerama).

  - Video works. No Xv however, so it's not particularly fast.

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Ticket URL: <http://dev.laptop.org/ticket/10210>
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