kern/49398: i386-current GENERIC (i915drmkms) boot hangs if monitor powered off

[jdbaker%mylinuxisp.com@localhost]

>Number:         49398
>Category:       kern
>Synopsis:       i386-current GENERIC (i915drmkms) boot hangs if monitor powered off
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Nov 17 03:25:00 +0000 2014
>Originator:     John D. Baker
>Release:        NetBSD/i386-7.99.1
>Organization:
>Environment:
NetBSD gx260a 7.99.1 NetBSD 7.99.1 (GENERIC) #82: Sun Nov 16 18:04:48 CST 2014  sysop%verthandi.technoskunk.fur@localhost:/d0/build/current/obj/i386/sys/arch/i386/compile/GENERIC i386

>Description:
Booting -current GENERIC (and probably netbsd-7 DRMKMS) kernel with
a monitor attached but powered off (no monitor attached?) hangs.

The machine in question is using a VGA CRT monitor for display.

Via a serial console:

[...]
pchb0 at pci0 dev 0 function 0: Intel 82845G/GL DRAM Controller / Host-Hub I/F Bridge (rev. 0x01)
agp0 at pchb0: i830-family chipset
agp0: detected 8060k stolen memory
agp0: aperture at 0xf0000000, size 0x8000000
i915drmkms0 at pci0 dev 2 function 0: Intel 82845G/GL Integrated Graphics Device (rev. 0x01)
drm: Memory usable by graphics device = 128M
drm: Supports vblank timestamp caching Rev 2 (21.10.2013).
drm: Driver supports precise vblank timestamp query.      
i915drmkms0: interrupting at ioapic0 pin 16 (i915)  
drm: initialized overlay support                  
[hung]

With video console, turning monitor on shows VGA text-mode
kernel messages which continue with:

drm kern error: Raw EDID:
[128 hex bytes]
[hung]

>How-To-Repeat:
Boot -current GENERIC (possibly netbsd-7 DRMKMS) i386 (amd64?) kernel
on machine with i915drmkms-supported hardware and monitor powered off (no
monitor?)

Have not tried on a radeon-equipped machine yet.
>Fix:
Workaround:  Always have monitor connected and powered on.