> ... as Stefan points out (thanks Stefan) this may not be so
> straightforwarded. I don't think this kind of tweaking is suitable
> for a setup that "Joe user" will get by default.
>
> Btw, if the video rom can be obtained directly from memory, why doesn't
> GRUB read it in runtime instead?
Actually, the modified rom is what we need, as it contains information
such as DDC table which is detected on POST, the original rom is not
very useful in this respect.
A better approach would be to fetch the rom from pci, then emulate the
POST process in grub2. But this need to port code from x86emu.
Default boot.efi passes to OSX kernel a blob device-properties containing some information about graphic and sound card. I'm nearly sure that it's retrieved from EFI and have an idea how but am not entirely sure yet. Here is an example from Florian Idelberger's dump from MBA who kindly permitted me to publish it
device-path (like in EFI specifications): 02 01 0c 00 d0 41 03 0a 00 00 00 00 01 01 06 00 00 02 7f ff 04 00
"saved-timing0"
length: 160
bytes: 13 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80 9b 82 07 00 00 00 00 80 9b 82 07 00 00 00 00 80 9b 82 07 00 00 00 00 00 05 00 00 90 01 00 00 10 00 00 00 90 00 00 00 c0 03 00 00 28 00 00 00 01 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
"saved-timing1"
length: 160
bytes: 00 10 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20 43 52 04 00 00 00 00 20 43 52 04 00 00 00 00 20 43 52 04 00 00 00 00 00 05 00 00 a0 00 00 00 30 00 00 00 20 00 00 00 20 03 00 00 17 00 00 00 03 00 00 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
"saved-config"
length: 256
bytes: 00 00 00 00 01 00 00 00 09 d1 00 00 c4 76 00 00 01 00 00 00 80 9b 82 07 90 06 00 00 00 05 00 00 90 06 00 00 10 05 00 00 a0 05 00 00 e8 03 00 00 c0 03 00 00 e8 03 00 00 c1 03 00 00 c4 03 00 00 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 13 00 00 80 06 10 00 00 73 9c 00 00 00 00 00 00 20 43 52 04 a0 05 00 00 00 05 00 00 a0 05 00 00 30 05 00 00 50 05 00 00 37 03 00 00 20 03 00 00 37 03 00 00 23 03 00 00 29 03 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 1a 00 00 00 00 10 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
"AAPL,backlight-control"
length: 4
bytes: 01 00 00 00
"AAPL,NumDisplays"
length: 4
bytes: 04 00 00 00
"AAPL,DisplayConfig"
length: 32
bytes: 13 00 00 00 00 00 00 01 21 00 00 00 00 00 00 00 41 00 00 00 00 00 00 00 81 00 00 00 00 00 00 00
"AAPL,HasPanel"
length: 4
bytes: 01 00 00 00
"AAPL,HasLid"
length: 4
bytes: 01 00 00 00
"AAPL,NumFramebuffers"
length: 4
bytes: 02 00 00 00
"AAPL,SelfRefreshSupported"
length: 4
bytes: 01 00 00 00
"AAPL,BacklightRestore"
length: 4
bytes: 01 00 00 00
"AAPL,BacklightMax"
length: 4
bytes: 56 00 00 00
"AAPL,aux-power-connected"
length: 4
bytes: 01 00 00 00
"AAPL01,T1"
length: 4
bytes: 00 00 00 00
"AAPL01,T2"
length: 4
bytes: 01 00 00 00
"AAPL01,T3"
length: 4
bytes: c8 00 00 00
"AAPL01,T4"
length: 4
bytes: c8 00 00 00
"AAPL01,T5"
length: 4
bytes: 01 00 00 00
"AAPL01,T6"
length: 4
bytes: 00 00 00 00
"AAPL01,T7"
length: 4
bytes: 90 01 00 00
"AAPL01,InverterFrequency"
length: 4
bytes: aa 01 00 00
"AAPL01,LinkType"
length: 4
bytes: 00 00 00 00
"AAPL01,DualLink"
length: 4
bytes: 00 00 00 00
"AAPL01,DataJustify"
length: 4
bytes: 01 00 00 00
"AAPL01,LinkFormat"
length: 4
bytes: 00 00 00 00
"AAPL01,PixelFormat"
length: 4
bytes: 00 00 00 00
"AAPL01,Inverter"
length: 4
bytes: 00 00 00 00
"AAPL01,Dither"
length: 4
bytes: 00 00 00 00
"AAPL01,InverterCurrent"
length: 4
bytes: 00 00 00 00
"AAPL01,BacklightIntensity"
length: 4
bytes: 1a 00 00 00
"AAPL01,CurrentDisplay"
length: 4
bytes: 00 00 00 00
"AAPL01,Height"
length: 4
bytes: 20 03 00 00
"AAPL01,Width"
length: 4
bytes: 00 05 00 00
"AAPL01,Depth"
length: 4
bytes: 20 00 00 00
"AAPL01,Refresh"
length: 4
bytes: 3d 00 00 00
"AAPL01,Interlace"
length: 4
bytes: 00 00 00 00
"AAPL01,Stretched"
length: 4
bytes: 00 00 00 00
"AAPL01,EDID"
length: 128
bytes: 00 ff ff ff ff ff ff 00 06 10 73 9c 01 01 01 01 10 11 01 03 80 1d 12 78 0a 90 b5 99 58 52 8e 26 1e 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 52 1c 00 a0 50 20 17 30 30 20 36 00 1e b3 10 00 00 18 00 00 00 01 00 06 10 20 00 00 00 00 00 00 00 00 0a 20 00 00 00 fe 00 42 31 33 33 45 57 30 33 20 56 30 0a 20 00 00 00 fe 00 43 6f 6c 6f 72 20 4c 43 44 0a 20 20 20 00 d4
"AAPL01,IODisplayMode"
length: 4
bytes: 00 10 00 80
"AAPL01,Pipe"
length: 4
bytes: 01 00 00 00
"AAPL01,BootDisplay"
length: 4
bytes: 01 00 00 00
"AAPL01,blackscreen-preferences"
length: 4
bytes: 00 00 00 08
"AAPL00,blackscreen-preferences"
length: 4
bytes: 00 00 00 08