Re: [PATCH] vgacon: Workaround for resize bug in some chipsets

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Antonino A. Daplas, le Sun 13 Nov 2005 06:20:53 +0800, a écrit :
> "I updated to the development kernel and now during boot only the top of the
> text is visable. For example the monitor screen the is the lines and I can
> only  see text in the asterik area.
> ---------------------
> | ****************  |
> | *              *  |
> | *              *  |
> | ****************  |
> |                   |
> |                   |
> |                   |
> ---------------------

Are you missing some left and right part too? What are the dimensions of
the text screen at bootup? What bootloader are you using? (It could be a
bug in the boot up text screen dimension discovery).

> I have a Silicon Graphics 1600sw LCD panel with a Number Nine Revolution 4
> video card."

Does vgacon.c properly discovers that it is a VGA board?

> This bug seems to be a glitch in the VGA core of this chipset.  Resizing
> the screen triggers the mentioned bug.

Do vga-only games (like old DOS-mode games) work with it?

> The workaround is to make vgacon avoid calling vgacon_doresize() if the
> display parameters did not change.

I.e. never call it, actually.

> A definitive fix will need to be provided by someone who knows and has the
> hardware.

I'm not sure it is hardware-specific. Maybe you have a combination of
vga bios/bootloader/vga=ask/... that prevents vgacon.c from properly
discovering the dimensions of the text screen.


Well, else it looks like a "safe side" patch: people now hit by such bug
won't be hit any more unless using stty or such.

Regards,
Samuel
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