Re: [PATCH v2 1/1] Split VGA default device handler out of VGA arbiter

On 24 August 2017 at 01:57, Dave Airlie [off-list ref] wrote:

quoted

Yeah, maybe it's time to disconnect the "default display device" idea
from the VGA arbiter.  I have no idea what (if any) dependencies X has
on the legacy VGA resources.  I assume X works fine on power, where it
sounds like those resources are rarely or never available.

The question on non-x86 archs, is what is the correct device to default to.

On x86 we use the legacy VGA resources as a pointer, as this is the device
the BIOS appeared on at boot so hopefully should be one you can see stuff on.

On non-x86 I've no idea how to decide if there are multiple devices, maybe the
firmware needs to tag something for the kernel if there are. Otherwise
you'd just
be picking something in probe order.

I think the idea of these patches is to separate default display
device from the arbiter.

X uses the arbiter on x86 if required (it's horrible, and it's rare we
have to nowadays),
but for finding the default device it justs uses the sysfs boot_vga flag.

Part of the problem is that X refuses to start if there is only one
display device to begin with in case it hasn't taken ownership of the
VGA legacy resources.