[Intel-gfx] [PATCH] drm/i915: Fix DDC bus selection for multifunction SDVO

[Adam Jackson]

On Wed, 2010-05-05 at 15:38 +0800, ykzhao wrote:

> Hi, Ajax
>    
>     Using the BIOS-defined value in VBT can fix the bug you mentioned.
> but the problem is that it is static and would still have problem if
> user does outputs swap on a multiple function SDVO device at run
> time(E.g. The external monitor is changed from SDVO-VGA to SDVO-DVI). 
>     Indeed, there is a SDVO specification that we use to write the SDVO
> code(Unfortunately, it's not white-washed yet to be released publicly).
> There is a predefined priority scheme described in the specification
> that driver and HW vendor need to follow, in order to pick up the
> correct DDC bus on the SDVO device that supports multiple outputs. For
> example, the RGB0 will have higher priority than TMDS0 if both
> RGB0/TMDS0 exist. RGB0 should use DDC1 and TMDS0 use the DDC2.)
> 
> What do you think the following patch? Would it work for the bug
> reported on redhat bugzilla584229?

I don't think this is correct, though I haven't tried it.  RGB0 and
TMDS0 are both going to be the same DVI connector for DVI-I.  If they
use different DDC buses, one of them won't get DDC, ever, since DVI-I
only has one set of DDC pins.

- ajax
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