[Intel-gfx] [PATCH 1/2] drm/i915/crt: Remove 0xa0 probe for CRT

[Keith Packard]

On Tue, 5 Apr 2011 10:19:16 +1000, Dave Airlie <airlied at gmail.com> wrote:
> On Tue, Apr 5, 2011 at 2:26 AM, Keith Packard <keithp at keithp.com> wrote:
> > On Mon, 04 Apr 2011 16:29:55 +0100, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> >
> >> Yes. I'm saying that that the controller accepts a write to port 0xa0.
> >
> > So it's the GMBUS controller itself then, I guess. Weird.
> >
> > Let me see if I understand how it used to work and why fixing the GMBUS
> > reset causes it to break in this case.
> >
> 
> I could be missing something here, but aren't i2c addresses 8-bit in this case?
> 
> 7-bit addr + direction bit, which means 0xa0 isn't valid i2c address,
> since in Linux
> the read/write bits are specified separately.

Could this be is a mis-translation of some X server code? The X
server stuck the direction bit in the LSB of the I2C address and
required that the drivers shift the register up and add the direction
bit manually (yes, a terrible API).

This is starting to make a lot more sense now. 0xa0 == 0x50 << 1.

-- 
keith.packard at intel.com
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