Overruling BIOS Panel size for 852GM

Keith Packard keithp at keithp.com
Sat Aug 5 07:57:10 PDT 2006

On Sat, 2006-08-05 at 11:27 +0200, Erwin Rol wrote:

> When I try to setup 1280x800 mode the driver complains that only modes
> 320x200 to 1024x768 are allowed. It seems to find the BIOS settings of
> the panel and reports that as;
> (II) I810(0): Found panel of size 1024x768 in BIOS VBT tables

The driver currently believes the VBT tables and ignores anything else
you might mention about the panel size, I'm afraid. That's because you
can't program an arbitrary mode for the panel, and using the wrong mode
can destroy it.

Normally, the VBT tables include the precise panel timings, but in your
case they don't.

> This is with the modesetting branch, I couldn't get it to work with the
> normal 1.6.1 release at all. Using the 915resolution program does not
> help, it still find the 1024x768 VBI entry and refuses to change the
> resolution. 

Yup; even modesetting has to find the panel mode somewhere, and the BIOS
(so far) has always been a reliable source.

> Any idea how to over rule this ? Can it done in the xorg.conf file or
> should I hack the i810 driver ?

The only way you're going to override it is to hack the driver. You'll
want to use the modesetting branch as that will only require minor edits
to change where it gets the timing information. It "should" be easy to
change the code to use a user-specified mode for the LVDS by just
skipping the LVDS VBT overrides.

BTW -- if you've got control over the BIOS as it will be shipped, I'd
recommend sticking the LVDS timings in the VBT tables as you'll be able
to swap panels without changing any other configuration.
keith.packard at intel.com
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