[Intel-gfx] [PATCH] drm/i915: no LVDS on Intel SandyBridge SDVs

[Chris Wilson]

On Tue, 21 Dec 2010 12:12:42 -0800, Keith Packard <keithp at keithp.com> wrote:
> On Tue, 21 Dec 2010 19:55:15 +0000, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> 
> > The test we do is simply whether the LVDS i2c pins are addressable. That
> > requires differentiating between an IO error and a NAK, which at present
> > is only possible using GMBUS. The reference to this method I found in the
> > BIOS writers' guide, but of course that doesn't actually explain how it
> > works (especially the significance of address 0xa0).
> 
> I can't see how that would work without an i2c receiver on the DDC
> bus...
> 
> But, then, I've been surprised by DDC in the past, so perhaps it's worth
> a test on a device that has LVDS but does not have EDID.

It works as far back as I can test, a 915GM without a VBIOS or EDID.
I've had one person report that it can distinguish a phantom LVDS panel on
one g33 based all-in-one computer. Though not all hardware is equal, and
prudence suggests wider testing. ;-)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre