From: Alan Hourihane <[EMAIL PROTECTED]>
To: Raymond Jennings <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED]
Subject: Re: Could the VESA BIOS be of assistance? (ID 20311056 ignore this filter)
Date: Mon, 24 Nov 2003 21:26:50 +0000
On Mon, Nov 24, 2003 at 09:19:01PM +0000, Raymond Jennings wrote:
> I was wondering if we could make some use of the VESA VGA extension, to set
> video modes at least. That would eliminate all of the video mode problems,
> such as bad offsets, out of sync, and scanline problems. The VESA standard
> covers everything the XVidMode extension does, but does it more safely. I
> have yet to see the video bios mess up the video card. The XVidMode
> extension could ignore everything but the screen dimensions and be backward
> compatible. Xvidtune would be made obsolete. I've done plenty of VESA
> hacking, and it seems a promising interface.
>
> And don't tell me it's slow, because the video card takes a while when
> changing video modes anyway, and any latency involved in calling the VESA
> BIOS would be masked by the monitor resyncing.
>
> Tell me what you guys think about this. I'm aware of a prejudice against
> the BIOS, but this is a special case. I know for a fact that messing
> around with sync frequencies is dangerous, and the BIOS can be trusted.
>
> You could make use of the vm86 system call, or write a kernel module to go
> to v86 mode on behalf of the X server. I'm certain there's always a way to
> get to the VESA extension.
>
> Let me know what you guys think. Is this practical? is it ingenious? Is
> it dangerous? Is it stupid?
The driver for using the VESA BIOS already exists and has done for several XFree86 versions. The driver is called 'vesa'.
Some drivers already use BIOS calls to set modes too, some of the Intel chipsets exclusively use it.
Alan.
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