Hotplug CPU

[fleming at austin.ibm.com]

> My understanding is that things will end up in the sysfs filesystem.
> There is already some support for cpu features there (eg cpu
> frequency).

Okay... I have discovered the sysfs interface.  I haced up a boot-time
routine to call register_cpu() for each boot-time cpu.  I then have a
/sys/devices/sys/cpu? directory fr each CPU in my machine.

The name file correctly has the name as printed by register_cpu.
There are two other files, online and power.  'online' appears empty
when I cat the file, and 'power' has just the string "0\n" in it.  The
show_online and store_online functions registered with the device do
not seem to be called, as the info that show_online produces is not
showing up.

I've read the documentation in sysfs.txt several times and I still
don't understand where the 'online' and 'power' files are coming from,
nor which sysfs file should be calling out to show_online() when I
read it.

Lastly and mostly unrelated, at what point during boot will printk()
be successful?  It's getting hard to debug when I can't even use
printk's to track execution...

Thanks, and TIA,
Matt
--
fleming at austin.ibm.com

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