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

["Antonino A. Daplas" <adaplas@gmail.com>]

Samuel Thibault wrote:
> 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).

It was just the height.  All numbers (done with printk's) look okay from
bootup. He gets 80 and 25 for ORIG_VIDEO_NUM_COLS and ORIG_VIDEO_NUM_LINES
respectively.

> 
>> 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?

Yes.

> 
>> 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.

His console worked before linux-2.6.14-rc2.

Tony