Re: [9front] strange behaviour of igfx and vesa

[cinap_lenrek@felloff.net]

state. the vesa bios might initialze registers that the igfx
driver misses.

"blank screen" doesnt say much. do you get a stable, but
black screen? or does the screen not even turn on? is the
backlight just off?

you can dump the register contents with aux/vga and compare
native igfx vs vesa + igfx.

this will only catch register differences that igfx knows
about tho.

it is possible to run realemu in trace mode (-p) and log all
the io reads and writes while vesa programs the card. then
sort thru the log to identify registers that the driver doesnt
know about.

i'v written some scripts to decode realemu bios traces that
you could adapt for your card:

http://felloff.net/usr/cinap_lenrek/igdump.tar

you certanly have to change the port offsets for the banked
address/data register in mmio.awk (check the io bar of
the graphics card of your system)

in any case, make a realemu trace (from the initial no-graphics
state). so we get a real detailed programming sequence for the
card that is known to work. once we have that, it is possibe
to figure out what we are missing or where igfx diverges.

dont run the realemu trace when grapics is already running.
because vesa might skip initialization of registers that have
already been programmed, so you'll not catch the missing bits.

--
cinap