[Intel-gfx] [PATCHv5] drm/i915: Enable SDVO hotplug interrupts for HDMI and DVI

[Simon Farnsworth]

On Wednesday 21 September 2011, Keith Packard <keithp at keithp.com> wrote:
> On Wed, 21 Sep 2011 10:08:13 +0100, Simon Farnsworth 
<simon.farnsworth at onelan.co.uk> wrote:
> > I'm clearing the bits (&= not |=). I could respin setting it to 0, but
> > that takes me even further from the old (commented out) code, and I'd
> > really want someone to check SDVO specs before doing that.
> 
> What I see the code doing is asking whether devices 0 and 1 *could*
> support hotplug and then unconditionally setting the devices for which
> we *want* hotplug to that.
> 
> I think you should set the list of devices requesting hotplug to be the
> intersection of the set of devices which *could* do hotplug and the
> set of devices for which we *want* hotplug.
> 
> That seems like it would be achieved by just clearing the set of devices
> that we will request hotplug for and then checking which ones are
> supported and incrementally adding those to the hotplug_active set.

I think I see my mistake - but I'd like to check before I do a v6 of this 
patch.

I'm ANDing the value returned by hardware with 3 - I should be ANDing it with 
an appropriate ~3. The rest of the code (setting those bits in 
intel_sdvo_dvi_init based on what functions I have) should be OK.

Essentially, I'm fairly confident based on empirical evidence that bit 0 is HPD 
for device 0 (as my SDVO devices both return 0x01 in that byte). I don't know 
what the rest of the bits mean, but it seems like a reasonable guess that bit 
1 is HPD for device 1, so I'm acting accordingly.

I would still like someone with the spec to go over what I'm doing - this 
seems appropriate, but *all* I have to test against are two different 
motherboards with "integrated" DVI-D that turns out to be an SDVO device.

I have no documentation for SDVO - all of this is based on the existing code 
with hints from ajax; it could be complete nonsense for anything other than 
the two devices I have.
-- 
Simon Farnsworth
Software Engineer
ONELAN Limited
http://www.onelan.com/