Is a delay always necessary? Sleeping 500 ms would be quite noticiable: could we optimistically try without it, and only do it when necessary?

(Does it matter whether the previous write was redundant (i.e. when pwmX_enable was already set)?)

I've set the delay to 0.2s now. I've been spamming it and it still behaved correctly, though 0.5s wasn't that noticeable, at least to me. Setting fan speed now takes about 0.3s as a whole, which feels instantaneous (it was ~0.1s previously).

There's no way to do it optimistically, it may accept setting the speed twice and fail the third time, out of the blue (without me spamming the commands, during normal testing). And we can't read the pwmX_enable value either, because that also triggers sending HID reports to the device to read the state (aside from sensor reports, the driver does not cache anything else).

What I previously had in mind was something like:

# pseudo-code, I don't know the exact failure mode when the device isn't ready
try:
    self._hwmon.write_int(hwmon_pwm_name, pwm_duty)
except OSError:
    # Maybe the device couldn't handle the quick succession of reports; try one more time after a bit.
    time.sleep(0.5)
    self._hwmon.write_int(hwmon_pwm_name, pwm_duty)

But a 0.2 s delay is already a lot better, and keeps things simpler, so I actually prefer it.

For the record, the driver responds with -ENODATA.

Thanks!