Phantom pain with windfarm on diskless iMac G5

[Markus Demleitner]

Hi,

I tried 2.6.15 on my diskless iMac G5 clients today, resulting in
747 emulation mode (vrooom...!).  It turns out windfarm was
querying the hard disk temperature sensor, which usually is mounted
on the mounting bracket Apple uses.  We made the mistake of removing
these (from about 30 machines:-(), which in turn made
windfarm_lm75_sensor.c:wf_lm75_get return ffff, which translates into
about 255 degrees celsius.  No wonder windfarm pumped like there's no
tomorrow.

I've "fixed" this by returning some fixed low temperature if I see
ffff in wf_lm75_get for now, but I *guess* it would be nice to have
some way to detect the absence of the sensor (and tell it from a
simple failure).  However, the OF device trees still list the sensor
and even the hard disk itself even on the diskless machines.

Even if there were a way to detect the absence of the sensor, there's
still the problem that windfarm_pm81.c insists on having a hd temp
sensor to work, so a fix would probably require spoiling that
wonderful
	if (sensor_cpu_power && sensor_cpu_temp && sensor_hd_temp)
in there and replacing it with something like
  if (sensor_cpu_power && sensor_cpu_temp && (machine_has_hd() 
		&& sensor_hd_temp))
where I have no idea how to implement machine_has_hd().  A further
similar hack would spoil wf_smu_sys_fans_tick, and uglyness prevails.

In short: Am I doomed to hack the kernels of my diskless clients to
eternity (or retrofit the sensors)?  Or is there a sane way to treat
that kind of problem?

Thanks,

        Markus