[9front] Screen resolution

[Nicola Girardi <ng@0x80.stream>]

Hi all,

this weekend I moved from a RPi 2B+ to an Intel NUC.  Recent
discussions on this list motivated me to finally try that move.  My
only problem is that I can't seem to change screen resolution from
monitor=vesa vgasize=1024x768x16.

My sysinfo is at http://sysinfo.9front.org/src/498/body and the
relevant bits, I think, are:

...
vesa product        Intel(R) Sandybridge/Ivybridge Graphics Controller
...
edid 3840x2160@30Hz 
		clock=297
		shb=4016 ehb=4104 ht=4400
		vrs=2168 vre=2178 vt=2250
		hsync=+ vsync=+ 
...
0.2.0:	vid  03.00.00 8086/0166  11 0:f7800004 4194304 2:e000000c 268435456 4:0000f001 64
	Intel Corporation 3rd Gen Core processor Graphics Controller

A bit of grepping led me to /sys/src/9/pc/vgaigfx.c:/0x0166/ from
which I guessed I should run

@{ rfork n; aux/realemu; aux/vga -m igfx -l 3840x2160@30Hz }

The command blanks the screen and I'm not able to get it back (even by
issuing another aux/vga command known to work) and at that point I
reboot.  My suspicion is that I need to add an entry to /lib/vgadb but
I can't figure out what the entry should look like.  (The command
above, I think, is the same command I used to get 4K to work in some
other computer in the past; I didn't need to touch /lib/vgadb then.)

I read vga(3), vga(8), realemu(8), vgadb(6), but I can't figure this
out based on that (my understanding of some part of the manual is not
great).

Thanks for any help...

Nicola