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Re: Equivalent of ioperm / iopl in linux mips ?

To: Geert Uytterhoeven <>
Subject: Re: Equivalent of ioperm / iopl in linux mips ?
From: "Maciej W. Rozycki" <>
Date: Mon, 22 Apr 2002 17:30:08 +0200 (MET DST)
Cc: Wayne Gowcher <>, Linux-MIPS <>
In-reply-to: <>
Organization: Technical University of Gdansk
On Mon, 22 Apr 2002, Geert Uytterhoeven wrote:

> >  Hmm, I admit I haven't looked at this matter, but aren't
> > in/out/ioperm/iopl implemented as library functions in glibc like for
> > other architectures doing MMIO?  E.g. Alpha does this an it makes porting
> Perhaps. Note that you still need some /proc magic to find out the correct
> address to map. Or you can use /dev/ports.

 Well, for Alpha ioperm/iopl functions check the system type in
/proc/cpuinfo (we seem to have enough information there as well) and
failing this they check a result of readlink of /etc/alpha_systype.  Then
an appropriate region of /dev/mem is mmapped with per-page permissions set
up as requested if ioperm is used (with a worse granularity, though) and
subsequent in/out function invocations access the area as appropriate. 
See sysdeps/unix/sysv/linux/alpha/ioperm.c in glibc for details -- it's a
pretty clever solution with good performance and only a few trade-offs.

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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