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  10. May 09, 2008
    • Mike Isely's avatar
      Implement option to ignore external fixed mode settings · 7fb914a5
      Mike Isely authored and Zhenyu Wang's avatar Zhenyu Wang committed
      
      The Intel xorg driver tries mightily to determine the native fixed
      panel mode settings for the LVDS output.  It does this through various
      means, including scanning video BIOS tables, and noticing if the pipe
      in question has already been set up by somebody else (and adopting
      those timings).  This strategy works well for say a laptop where the
      LCD panel is an integral part of the machine.  But for other
      applications where the display is unrelated to the system's BIOS or
      other software, then the BIOS will likely have no clue how to
      configure the LVDS output.  Worse still, the BIOS can simply "get it
      wrong", leaving the pipe misconfigured.  Unfortunately the Intel
      driver can potentially notice this, adopt the same settings, leaving a
      messed up display.
      
      All of this complexity normally happens independently, behind the
      scenes, from the mode timings that might otherwise be specified by the
      user.  This driver has a concept of fixed, i.e. "native" mode, and
      then user-specified mode.  If the corresponding resolutions between
      those concepts don't match, then the driver in theory will arrange for
      scaling to take place while adhering to the actual native mode of the
      panel.  Said another way, if the user says 800x600 but the driver
      mistakenly (see above) thinks the native mode is 640x480, then 640x480
      is the mode set with scaling to an 800x600 frame buffer.  If the
      driver gets the wrong native mode, then the result is a miserable mess
      with no way for the user to override what the driver thinks is right.
      
      This patch provides a means to override the driver.  This implements a
      new driver option, "LVDSFixedMode" which defaults to true (the normal,
      probe-what-I-need behavior).  However when set to false, then all the
      guessing is skipped and the driver will assume no fixed, i.e. "native"
      mode for the display device.  Instead with this option set to false,
      the driver will directly set the timings specified by the user,
      providing an escape hatch for situations where the driver can't
      correctly figure out the right mode.
      
      Under most scenarios of course, this option should not be needed.  But
      in situations where the Intel video BIOS is hopelessly fouled up
      related to the LVDS output, this option provides the escape hatch for
      the user to get a working display in spite of the BIOS situation.
      
      Signed-off-by: default avatarMike Isely <isely@pobox.com>
      (cherry picked from commit 9f324860)
      7fb914a5
  11. May 08, 2008
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