[lm-sensors] The new thermal management sysfs class, and hwmon

[Jean Delvare]

On Fri, 22 Feb 2008 11:54:06 +0100, Hans de Goede wrote:
> Zhang, Rui wrote:
> > Hi, Hans,
> > 
> > On Fri, 2008-02-22 at 16:00 +0800, Hans de Goede wrote:
> > 
> >> I think all that is really needed and asked for is for the new thermal
> >> ACPI
> >> code to:
> >> 1) provide temp readings in the same format as hwmon (so milli degrees
> >> celcius,
> >> not degrees celcius
> > Agree.
> >> 2) provide a hwmon interface so that tools like (but not limited too):
> >> * net-snmp
> >> * mrtg
> >> * sensors
> >> * sensors-applet (gnome)
> >> * xfce-sensors-applet
> >> * ksysguard
> >> * ksensors
> >> * gkrellm
> >>
> >> Can provide temp and fan readings without having to be modified.
> > hmm, for fan device, maybe something like this?
> > pwm[1-*]_enable = 1 : manual fan control (using pwm[1-*])
> > 		  2+: automatic fan control (by acpi thermal driver)
> > pwm[1-*] = 0  : fan is off.
> > pwm[1-*] = 255: fan is on.
> > pwm[1-*] has only two valid values as ACPI fan only support 
> > two states, ON/OFF. and it doesn't need fan[1-*]_input because the fan
> > speed is not available.
> > Yes, it can work for ACPI fan although I don't think the existing pwm
> > hwmon I/F maps well to what we need and it seems like a "forced fit" to
> > use it. Any better ideas? :)
> > 
> 
> I wouldn't expose a pwm interface, doing so isn't that important as none of the 
> above listed apps actually use it, the pwm interface really only is for people 

Note: libsensors itself doesn't care about the pwm files.

> who want to manually tweak their fan speed and / or use some scripts to control 
> the fan speed based on temp when the hardware doesn't support it, as such it 
> doesn't get widely used, also since there isn't a really good mapping between 
> acpi thermalzone stuff and the hwmon pwm interface I wouldn't add a pwm 
> interface to a hwmon interface the the thermal zone code.
> 
> And if fan speeds aren't available (aren't they?) then I would only add a hwmon 
>   class reference to a sysfs dir containing tempX_input's and a name atrribute 
> and leave it at that.
> 
> But thats just my 2 euro-cents

FWIW, I agree with pretty much everything Hans said.

Additionally, we could map the critical trip point to tempX_crit (read-only).

Note that since lm-sensors 3.0.1, libsensors accepts hardware
monitoring attributes in the hwmon "class" device directory, and I
recommend doing this so as to have a separate namespace. This will
ensure that we don't get name collisions, and it makes things cleaner
anyway.

-- 
Jean Delvare