Re: [PATCH] x86: Reserve legacy VGA MMIO area for x86_64 as well asx86_32

From: Alan Cox
Date: Fri Apr 09 2010 - 18:50:54 EST


> No they're not. The 0xa0000...0xbffff range has been a legacy video
> area since the very first PC (although the first PC only used
> 0xb0000..0xbffff, 0xa0000..0xbffff was declared reserved at that time.)

Depending on your definition of "PC". Quite a few early MSDOS systems had
video elsewhere. Some embedded systems without video use the space for
other stuff. Lots of ISA 386/486 PCs had cards borrowing the unused bits
of video space.

> I'm wondering what those legitimate reasons are. This is particularly
> so since it affects our ability to deal with very early errors, long
> before we have enumerated anything. At this point we can at least lay
> down bytes in the video area and hope the user can see them.

Thats why you have the bios equipment byte and video queries.
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