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Re: software interrupts from a multiboot-compliant kernel

From: Alex Thiel
Subject: Re: software interrupts from a multiboot-compliant kernel
Date: Mon, 11 Feb 2002 13:40:11 +0100

On Sunday 10 February 2002 19:38, Timmy Douglas wrote:
> I made a multiboot compliant kernel using the demo files that came
> with grub: boot.S, multiboot.h, and kernel.c. I wanted to do some
> vesa/vga stuff and I figured out that software interrupts (int 10h)
> are probably the best way to do that.

Hello, Timmy!

I have just finished my patch to add VBE support to GRUB. I have attached the 
diff against the current CVS repository.

In principle, the kernel requests the video mode at boot time and then GRUB 
passes all the VBE info that you need to the multiboot kernel. It should then 
not be necessary to switch to real mode.

It would be great if you could play around with this a bit since I did not 
have time to actually implement graphics in my own toy kernel and try it out.

I have organized the VBE stuff as follows:
* init_bios_info in common.c checks for a VBE bios.
* load_image in boot.c selects the video mode if a multiboot kernel requests 
* boot_func in builtins.c switches the video mode before calling the kernel

I have also allowed myself to change the multiboot specification a bit: the 
VBE info now goes into a seperate table, like the APM info.

I was thinking about adding an interactive command to override the video mode 
chosen by load_image which falls back to text mode if it does not find the 
exact mode requested. Do you think this would be useful?

> if anyone could explain or provide an example for this---it would be
> great,

I am a beginner in assembler programming myself, I just copied the things I 
found in asm.S. Could anyone please explain the way this works?



> thanks for any help,
> _______________________________________________
> Bug-grub mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/bug-grub

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