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List:       xen-devel
Subject:    Re: [Xen-devel] VGA extended text modes
From:       Gerd Knorr <kraxel () bytesex ! org>
Date:       2005-02-28 17:25:46
Message-ID: 87wtss1tr9.fsf () bytesex ! org
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"Ian Pratt" <m+Ian.Pratt@cl.cam.ac.uk> writes:

> However, how does dom0 set the extended text mode? I presume it doesn't
> use a BIOS call.

Linux uses vesa bios calls in the 16bit startup code, at least for the
stuff settable via vga="...".  Mode info is passed to 32bit code in
struct screen_info (see Documentation/i386/zero-page.txt).  Thats why
the vga argument needs special treatment by the boot loaders, they
can't just pass it on on the kernel command line like most other args.
They have to set a byte in the kernel's boot sector for that.  See
also "man rdev".  That is really old stuff from the days you have
booted your new linux kernel using "cat zImage > /dev/fd0 && reboot".

For just more text lines you can simply load a smaller font than the
default one somewhere in the dom0 boot scripts to have the same
effect.  That doesn't work for 132col txt modes or graphic modes (=>
vesafb) though.

  Gerd

-- 
#define printk(args...) fprintf(stderr, ## args)


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