[Intel-gfx] DDC/CI on Q965 DVI port

[Chris Wilson]

On Mon, 20 Sep 2010 10:00:23 +0800 (SGT), Val Ferdinand Caro <valcaro at yahoo.com> wrote:
> I am doing a simple DDC/CI app (change brightness/contrast/etc...) For this 
> project I am scanning the PCI bus, identifying the device, getting the base 
> address and mapping it. Then using I2C bit algorithm on each GPIO register 
> 0x5010, 0x5014, 0x5018, 0x501C..., and 0x502C. The approach is similar with 
> "Linux ddccontrol" project. But this one is targeted only for Intel chipsets.

How do I say "don't do this" in a loud and clear manner? Those registers
are already used by the kernel and you are stomping over any communication
in progress. Use the i2c devices exposed by the kernel if you want to do
this from userspace.
 
> For my 855GM card, I can get EDID and do DDC/CI (send/write MCCS) on both VGA 
> and DVI ports.
> 
> Now the problem is the Q965 card, it only detects my VGA monitor and the digital 
> display doesn't. Am I missing something here that is different with the DVI 
> port? Any other registers that needs to read or written first?

No, but the pins and regs were moved around between generations and the
manufacturers were allowed to remap them to different functions as well.
Exactly how the driver is meant to discover this, the specs do not
clarify.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre