Who else is writing to the EC? (Sony Vaio S3XP / PCG-6E1M)

I'm a bit annoyed of the way the fan behaves in my Sony Vaio S3XP / PCG-6E1M. Basically it's totally disabled until ~55°C, then switches on and gets faster with higher temperature. However the system tends to oscillate with a ~1min period, which is very annoying. I would rather like the fan to be active at a slow speed all the time.

I noticed that there's no FAN-Resource in the DSDT.
There's no active cooling entry in the thermal zone, only a passive one at 50°C. A quick overview over the thermal zone in the DSDT didn't show any stuff where the fan is controlled.

Now there's a FAN0 entry in the embedded controller, at offset 0x93. I made a small hacking by making a kernel module which directly writes to the EC, and it works, i can set the fan speed between 0 and 0xFF.

However, about one second or so after i write the value, the fan speed gets reset to the original value. reading from the EC show that the value there gets reset, too.

I could not find any references inside the DSDT to the FAN0 resource in the EC, i searched for both 0x93 (the offset) and "FAN0".

Even when i remove the "thermal" module, the fan behaves exactly like before.

Who controls the fan when there's no thermal module active? Is there any way i can override the fan control on this machine?

the dsdt: http://tmb.elitedvb.net/dsdt
and the disassembled version: http://tmb.elitedvb.net/dsdt.dsl

thanks,
Felix

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