Using VESA BIOS in Framebuffer driver

Using VESA BIOS in Framebuffer driver

[seetaram Tekkalakot]

Hi Guys

I am developing a framebuffer driver for my PLC 69030 video card.
I have gone through the Source code of the Sample framebuffer driver and i have some clarifications needed. Please clarify my doubts.

1.How does the Frame buffer driver Switches graphics modes, i mean how does it initializes the graphics system say in 640*480*256 mode and switch to say 800*600*24 mode.
Does it depend on VESA BIOS calls to do this ?
Let me know.

2.How does the framebuffer driver achieve paging ?
Say my display memoy is 4mb and i want divide it into 4 pages then how will i do this ?

Please clarify my doubts

Thanks and regards
Seetaram
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Re: Using VESA BIOS in Framebuffer driver

[Cheshire Cat Fish]

--
A precariously balanced mixture of myopic optimism and rampant paranoia.
>I am developing a framebuffer driver for my PLC 69030 video card.
>I have gone through the Source code of the Sample framebuffer driver and i 
>have some clarifications needed. Please clarify my doubts.

I am in the process of doing exactly this for a custom board.  So this will 
be like the blind leading the blind I suspect, but for what it is worth, 
here is what I know...

>1.How does the Frame buffer driver Switches graphics modes, i mean how does 
>it initializes the graphics system say in 640*480*256 mode and switch to 
>say 800*600*24 mode.
>Does it depend on VESA BIOS calls to do this ?

I think this is up to you how you want to do this.  In mine, I do it by 
directly programming the hardware (no BIOS calls whatsoever).   Basically, 
you are told to set a mode - how you do that is up to you.

>2.How does the framebuffer driver achieve paging ?
>Say my display memoy is 4mb and i want divide it into 4 pages then how will 
>i do this ?

I'm not sure what you mean by paging.  Video memory isn't typically paged.  
Is not all 4MB available at once?

Noel.

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Re: Using VESA BIOS in Framebuffer driver

[James Simmons]

> I am developing a framebuffer driver for my PLC 69030 video card.
> I have gone through the Source code of the Sample framebuffer driver and 
> i have some clarifications needed. Please clarify my doubts.
> 
> 1.How does the Frame buffer driver Switches graphics modes, i mean how does
> it initializes the graphics system say in 640*480*256 mode and switch 
> to say 800*600*24 mode.

Well that is very hardware dependent. Which kernel are you working with?

> Does it depend on VESA BIOS calls to do this ?

NO!!! There does exist vesafb.c for this but this only works on a system 
with a BIOS. If you have a system with no BIOS you are out of luck.

> 2.How does the framebuffer driver achieve paging ?
> Say my display memoy is 4mb and i want divide it into 4 pages then how 
> will i do this ?

4 pages? 




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Enterprise Linux Forum Conference & Expo, June 4-6, 2003, Santa Clara
The only event dedicated to issues related to Linux enterprise solutions
www.enterpriselinuxforum.com