dev.fan_eft, aka, opt_bitmain_fan_ctrl, is controlled via command line or via config file, in history.

That invariant breaks beginning with buttmange's latest change to remove capability from the user.

So yes, you are correct regarding eft. However, it's the combination of eft and "pwm" that defines the fan speed. I use pwm in quotes there because it is a pseudo-thing in the implementation and gets converted into some shifted bytes that are written to the hardware.

Even if you were to get through that, you'll run into the threads that are managing the fan which will override what you are attempting.... and it may happen so fast you never see it.

I suspect they've removed some plumbing in the config file handling, but I haven't got to that point in my analysis yet.

-j