kern/50781: set hw.acpi.sleep.vbios=0 when kernel display driver handles suspend/resume (e.g., drmkms)

[riastradh%NetBSD.org@localhost]

>Number:         50781
>Category:       kern
>Synopsis:       set hw.acpi.sleep.vbios=0 when kernel display driver handles suspend/resume (e.g., drmkms)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 08 00:15:00 +0000 2016
>Originator:     riastradh%NetBSD.org@localhost
>Release:        NetBSD-current
>Organization:
>Environment:
>Description:

	hw.acpi.sleep.vbios is a kludge to enable the kernel to restore
	the display when it doesn't have a proper display driver, with
	two different methods corresponding to values 1 or 2.  But when
	we do have a proper display driver that already handles
	suspend/resume, only value 0, disabling the whole kludge, makes
	sense.

>How-To-Repeat:

	Attempt to suspend/resume with a DRM/KMS driver with hw.

>Fix:

	Unclear where the logic should go.