VGA extended text modes

VGA extended text modes

[Jared Rhine]

  Edward> I am trying to get the hypervisor to run in an extended text
  Edward> modes,

  Ian> When dom0 takes over the VGA console (which is the default mode
  Ian> of operation) you can arrange to put it into whatever mode you
  Ian> like; you just won't get the initial boot messages from Xen in
  Ian> the extended text mode.

  Edward> I was looking at modifying the hypervisor because I couldn't
  Edward> get this to work and couldn't find a specific reference
  Edward> stating it was possible.

  Jared> I too, have failed to set any vga mode for any Xen
  Jared> installation.  Could the developers confirm 1 more time that
  Jared> it "works for them" (if indeed) and we can try to
  Jared> characterize the bug more.

Apologies for following up to this thread for the third time, but near
as I can tell, this is an open issue.

Can anyone (developers especially) confirm or deny operation of
extended VGA modes in dom0?

XenCD comes with a handy boot menu item to serve as a repeatable test
case :)

-- jared@wordzoo.com

War is God's way of teaching Americans geography. -Ambrose Bierce


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RE: VGA extended text modes

[Ian Pratt]

>   Jared> I too, have failed to set any vga mode for any Xen
>   Jared> installation.  Could the developers confirm 1 more time that
>   Jared> it "works for them" (if indeed) and we can try to
>   Jared> characterize the bug more.
> 
> Apologies for following up to this thread for the third time, but near
> as I can tell, this is an open issue.
> 
> Can anyone (developers especially) confirm or deny operation of
> extended VGA modes in dom0?

To my knowledge I don't think any of us use extended VGA text modes. I
think we're just rather 'surprised' that it doesn't just work. After Xen
has relinguished the VGA console, domain 0 should be able to use it
however it pleases. 

However, how does dom0 set the extended text mode? I presume it doesn't
use a BIOS call. Perhaps it can't cope with the scroll state we leave
the console in?
The former would be a huge pain. Anything else is probably trivially
fixed once the cause is discovered.

Ian


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Re: VGA extended text modes

[B.G. Bruce]

I can't speak for anyone else but I know that at one time (about 2-3
weeks ago) a vga=ask allowed me to get into 80x60 mode under xen0 -
ultimately I swapped over to running intelfb in 1280x1024 but I know
that at least on my equipment (and my kernels) both of these work as 
per usual.

B.


On Sat, 2005-02-26 at 04:39, Jared Rhine wrote:
>   Edward> I am trying to get the hypervisor to run in an extended text
>   Edward> modes,
> 
>   Ian> When dom0 takes over the VGA console (which is the default mode
>   Ian> of operation) you can arrange to put it into whatever mode you
>   Ian> like; you just won't get the initial boot messages from Xen in
>   Ian> the extended text mode.
> 
>   Edward> I was looking at modifying the hypervisor because I couldn't
>   Edward> get this to work and couldn't find a specific reference
>   Edward> stating it was possible.
> 
>   Jared> I too, have failed to set any vga mode for any Xen
>   Jared> installation.  Could the developers confirm 1 more time that
>   Jared> it "works for them" (if indeed) and we can try to
>   Jared> characterize the bug more.
> 
> Apologies for following up to this thread for the third time, but near
> as I can tell, this is an open issue.
> 
> Can anyone (developers especially) confirm or deny operation of
> extended VGA modes in dom0?
> 
> XenCD comes with a handy boot menu item to serve as a repeatable test
> case :)
> 
> -- jared@wordzoo.com
> 
> War is God's way of teaching Americans geography. -Ambrose Bierce
> 
> 
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> SF email is sponsored by - The IT Product Guide
> Read honest & candid reviews on hundreds of IT Products from real users.
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> 


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Re: VGA extended text modes

[Gerd Knorr]

"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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