[Soekris] Error LED Control from Linux userland?
johnl at blurbco.com
Mon Apr 15 23:43:33 UTC 2002
The aliasing is only necessary for the linux SC520 watchdog timer
driver. It is also necessary if we wan't to take control of the MMCR and
its GPIO's from userspace since linux reserves that memory range for
kernel-only access. My kernel LED module works fine with the MMCR at
0xfffef000. I'll contact the author of the watchdog driver and see why
he requires an aliased MMCR. This whole thing may be somewhat of a
If it is an issue, though, my mmcr_alias module will soon have a io
memory check in it so that it won't clobber expansion roms and would
instead create the alias in an empty 4K page of unused ISA memory.
(actually as it is the loading would fail if the range is not available)
I think the BIOS is OK with no change, unless the *BSD folks can't
create a similar alias if necessary. Having the OS set up the mmcr alias
if needed is nicer since the OS can then be aware of the remapped page.
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