Hi Jean !
> In your case, the file would have only 3 possible values, with "off"
> mapping to 0, and "slow" and "fast" mapping to arbitrary positive
> values, like 64 and 192 or whatever you think is suitable. I understand
> that in your case, you don't really control the PWM output directly,
> but we do not have any interface for this, and I don't think there
> would be much value in adding one.
>
> That being said, I am also only mildly convinced that fitting your chip
> in the standard pwm1 interface will be very helpful. I don't really
> expect tools such as the fancontrol script to behave properly when the
> pwm1 file only support a small number of discrete values. So the
> benefit of using the standard file name and semantics seems thin.
Yes, I'm not too sure either.
> > Another comment while at it is when implementing the thermal control for
> > PowerMacs a while back (windfarm etc...) I had to deal with two
> > different type of interfaces to fans. RPM controlled and PWM controlled.
> >
> > The later basically let me program a percentile value (a percent of the
> > duty cycle).
>
> This is exactly what pwm[1-*] files are about, except that we used
> range 0-255 instead of 0-100 for historical and practical reasons.
Ok, I missed those in the doco.
> > I looks like the described sysfs interface only does RPM, or at least
> > doesn't provide a way to expose the units used...
>
> For RPM-controlled, look at the following entry instead:
>
> fan[1-*]_target
> Desired fan speed
> Unit: revolution/min (RPM)
> RW
> Only makes sense if the chip supports closed-loop fan speed
> control based on the measured fan speed.
>
> One significant difference is that, in this case, you always know which
> fan you control, while in the pwm[1-*] case you don't.
Right.
Now, maybe the best option is to have instead:
fan[1-*]_discrete_value
Discrete value
RW
fan[1-*]_supported values
List of supported discrete values
RO
IE. I like the interface to be self-explanatory rather than relying on
the user to know in advance what to write there. In which case I could
either use 0,1,2 as values or even "off, slow, fast".
I can then make a custom fancontrol script (or add a wart to the
existing one) to deal with this HW.
What do you think ?
Another option of course is to do the whole thermal control in a kernel
thread :-) That wouldn't be very hard nor take a lot of code, but I'm
sure I'll encounter resistance trying to merge that :-)
Cheers,
Ben.
_______________________________________________
lm-sensors mailing list
lm-sensors@xxxxxxxxxxxxxx
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
