Re: The new thermal management sysfs class, and hwmon

[Hans de Goede <j.w.r.degoede@hhs.nl>]

Zhang, Rui wrote:
> On Sat, 2008-02-23 at 16:29 +0800, Jean Delvare wrote:
>> 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.
> then we'll have have duplicate attributes for temperature and critical
> trip point, like:
> /sys/class/hwmon/
> |hwmon0
> 	|---name
> 	|---temp1_input
> 	|---temp1_crit
> 	|device		--->/sys/class/thermal/thermal_zone1
> 		|---type
> 		|---temp(in millidegree Celsius)
> 		|---trip_point_0_type:	critical
> 		|---trip_point_0_temp(in millidegree Celsius)
> 		...
> It's okay if we always keep these them in sync, right?
> 

Yes thats the whole idea, then lm_sensors using applications can get the info 
you add to the hwmon dir without having to learn yet another API (esp since 
allmost all these applications are always only reading things like temperature 
and maybe limits, and are not interested in the more advanced stuff.

Regards,

Hans