[LinuxBIOS] Re: VGA support

Steven J. Magnani steve at digidescorp.com
Thu Aug 11 15:57:50 CEST 2005

Yhlu writes:
> So at last for your linuxbios.rom, you should do 
> cat atix.rom linuxbios.rom > final_linuxbios.rom

I went through this exercise with my board last week, and this procedure
didn't work for me. Might be because there is nothing in the LB code
that prevents the memory range occupied by the video ROM from being
allocated to PCI devices.

What I finally ended up doing is creating a wrapper .S file for my
mainboard that pulls the video ROM into the compiled LB RAM image:

	.section .rodata.optionrom
	.globl	_vgarom_start
	.globl	_vgarom_end

In Config.lb I reference a symbol defined in the wrapper:

    chip drivers/pci/onboard
        device pci 0.0 on end
            register "rom_address" = "_vgarom_start"

...and in my mainboard chip.h I forward-declare the symbol, so static.c
can compile:

    extern unsigned char _vgarom_start[];

This strategy has the advantage of making the rom address independent of
changes in the size of LinuxBIOS or the payload. The disadvantage is
that the video ROM gets compiled into both the fallback and normal LB
RAM images (it takes up twice as much flash space as it needs to).

I am wondering if it might be useful for LB to support some kind of
flash partition structure (similar to Redboot) to allow storage of
things common to both fallback and normal images, or to support user
selection among two or more payloads.

 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"

 #include <standard.disclaimer>

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