Re: [PATCH 0/4] Get EDID late for VGA switcheroo

From: andreas
Date: Tue Jan 07 2014 - 09:48:37 EST

Am 2014-01-07 15:30, schrieb Ramkumar Ramachandra:
Seth Forshee wrote:

3. So what is really wanted is to be able to mux just the DDC over to
the IGPU when the device is initialized to read the panel mode. One
possible problem is that the hw might not support muxing the DDC
separately, but Apple hw does so we'll ignore that for now. The
basic code for muxing only the DDC isn't too difficult, and I had
some patches for this at one point. The problem is that the handler
must register with vga_switcheroo before this is possible, so
there's a module initialization ordering issue that wasn't easily
solved. Maybe now it would be possible to do something with
EPROBE_DEFER, though I'm not sure how i915 would know whether or not
it should wait for a switcheroo handler.

I didn't understand much of the above; I suppose it'll start making
sense when I'm deeper into the issue.

You can switch the line used to detect the display separately from the line which is used to display the picture, so you can just switch DDC to the intel card when you know it will try to detect the display, without having to introduce flickering. There were a few different versions of patches that did this, I think this one is the latest:

Sorry that I forgot about this yesterday, it has been quite some time since I worked on this.
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