[ubuntu-x] Hybrid graphics detection

[Eric Appleman]

On 11/03/2011 12:38 PM, Bryce Harrington wrote:
> On Thu, Nov 03, 2011 at 12:08:53PM -0400, Christopher James Halse Rogers wrote:
>> On Thu, 2011-11-03 at 08:50 -0700, Bryce Harrington wrote:
>>>>> Would it make sense to make that into a udev rule?
>>>> I'm not sure that a udev rule would have the necessary context, but
>>>> either a udev rule or an upstart script would absolutely make sense.
>>> Would any context be needed beyond loaded kernel gfx driver(s) and
>>> machine identification info?
>> I don't believe so, no.  But if we're writing a udev rule that needs to
>> be triggered on a udev event, and I'm not sure whether there's a udev
>> event that we can rely on to happen at an appropriate time.
>>
>> Right?
> At this point we should probably talk to slangasek about it.
>
> Bryce
>
While vga_switcheroo may be sufficient for turning off the Nvidia GPU, 
it is a a one-way trip for some Optimus laptops with the PEGP _DSM until 
a reboot. The card can be reenabled, but the kernel module won't 
reinitialize.

To that end, Alex Williamson (byo-switcheroo - requires specific ACPI 
calls) and Peter Lekensteyn (bbswitch - WIP; general ACPI calls) have 
been working on methods that save the card's state via PCI.

https://github.com/Lekensteyn/acpi-stuff/blob/master/bbswitch/bbswitch.c
https://github.com/awilliam/asus-switcheroo/blob/master/byo-switcheroo.c

- Eric