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: macro@ds2.pg.gda.pl, PGP key available +
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