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Re: [PATCH] Video mode fixes in linux loader

From: Pavel Roskin
Subject: Re: [PATCH] Video mode fixes in linux loader
Date: Mon, 13 Apr 2009 19:20:20 -0400

On Mon, 2009-04-13 at 21:05 +0200, Robert Millan wrote:
> On Mon, Apr 13, 2009 at 11:41:36AM -0400, Pavel Roskin wrote:
> > I actually installed GRUB with gfxterm on a laptop that has Intel
> > framebuffer support.  Now the kernel starts in VESA mode and then the
> > screen goes blank because intelfb cannot deal with it.  Sure, intelfb
> > should be fixed, but we should be liberal in what we accept.
> We could detect this situation by checking video= parameter, and setting
> text mode if intelfb is found.  But then again do we want to prevent
> future versions of intelfb from gracefuly transitioning from vesa mode
> without screen glitch?

No, that would be bad.  It's even possible that intelfb would work
correctly in other configurations.  The laptop has resolution 1440x900
that doesn't match any VESA mode.

> > Some
> > kernels may not support VESA modes at all.
> I don't think this is applicable;  all modern versions of Linux include
> vesa modesetting in its 16-bit entry code, and older versions are already
> detected by the new loader (user is prompted to use linux16).

I can disable CONFIG_FB, and then the screen remains blank until X
starts.  It's entirely possible that some distros don't enable CONFIG_FB
to save memory, and I don't always enable it in the kernels I configure

> > Adding vga=0 to the kernel command line didn't fix it.  That's bad.
> > "vga=0" means text mode 80x25.  Adding "vga=1" fixed the problem.  The
> > text mode was 80x25, not 80x50, so that's another issue.
> Shouldn't be hard to fix.  Do you know how to switch to 80x50 mode?

Well, load 8x8 font.  It's done in the 16-bit code.

> > "vga=ask" is not a warning now.  It causes "error: You need to load the
> > kernel first", apparently from initrd.  In other words, the "linux"
> > command fails and there is no visible warning.
> Sounds like my error code is wrong, but we could turn it into a warning
> like you suggested.

I was editing the command line from the menu, so I  could not see the
message.  Waiting for input is a fair game for an option that implies
waiting for input.

Pavel Roskin

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