Overruling BIOS Panel size for 852GM

Erwin Rol mailinglists at erwinrol.com
Sat Aug 5 12:54:29 PDT 2006

Hey Keith,

first of all thanks for your reply.

On Sat, 2006-08-05 at 07:57 -0700, Keith Packard wrote:
> 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.

That's a risk I could take, of course it would be a bit of a waste to
kill several panels, but the risk of killing one or two is less bad than
not being able to get things working in the first place. 

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

Nope the CPU-board BIOS is rather poor and does not support any wide
screen panels. 

> > 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.

Well i guess it is reliable when the right resolution is there :-)

> > 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.

I was already using the modesetting branch, i will try to hack things in
a way that i can get it working. This hacking might of course case some
more mails from me to the mailing list :-)

> 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.

I have no control over the BIOS at all :-/ So i have not much choice
here, I will talk to the manufacturer to ask if they maybe could do a
BIOS update that supports a few more panels.

- Erwin

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