[lkml]   [2001]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: isa_* problems (hgafb is broken since 2.4.13)
On Thu, 8 Nov 2001, James Simmons wrote:
> > I have two questions about asm-i386/io.h:
> > 1. Why #define __ISA_IO_base ((char *)(PAGE_OFFSET)) ?
> > 2. Why not #define __ISA_IO_base ((char *)0) ?
> For ix86 the ISA IO space start is at the very begining of memory. On
> other platforms like the PPC the ISA IO space is seperate from the
> regular memory space. It starts after the regular memory space thus the
> __ISA_IO_base will not be 0x0.

He's talking about asm-i386/io.h.

__ISA_IO_base (what's in a name, why not call it __ISA_MEM_base?!?!?) is the
kernel virtual address of the start of ISA _memory_ space. On ia32 PCs, ISA
memory space overlaps with the first 16 MB of real RAM, at CPU physical address

(DISCLAIMER: my ia32 knowledge is limited)



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:13    [W:0.073 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site