On Wed, May 11, 2011 at 1:20 PM, Kevin O'Connor kevin@koconnor.net wrote:
On Wed, May 11, 2011 at 01:12:16PM +1000, Graeme Russ wrote:
for two or three graphics chipsets. SeaBIOS can initialize any VGA option ROM, but then you need SeaBIOS in the loop. Option ROMs are ageold technology and stupid, but they are still firmly entrenched in PC hardware. A BIOS was always there so everyone assumes it will always stay there, not very many question if something better could be done.
Would be interesting to investigate implementing a stub in U-Boot to initialise and use VGA option ROMs
VGA option ROMs call BIOS functions. So, one needs a BIOS implementation (eg, SeaBIOS) or an emulator for them (eg, in coreboot).
What does Linux do? i.e. if you boot Linux from coreboot, how does it output to the VGA console? I know it uses BIOS early on (before switching to protected mode) but what does it do after entering protected mode?
In general, one enables the coreboot VGA option ROM emulation when booting Linux directly from coreboot.
Yes, I understand that - But how does Linux output to the VGA console after switching to Protected Mode? Does it still do BIOS calls?
And what about all those Linux drivers in drivers/video - Would porting them (to U-Boot) elliminate the need for BIOS/Option ROMs
Note: Please pardon my ignorance if these appear to be dumb questions - I really don't know how the guts of VGA console works
Regards,
Graeme