echo 75000 > /sys/class/thermal/thermal_zone0/trip_point_1_temp - Permission denied!!

[John Hupp]

On 6/18/2014 1:21 PM, Tapio Valli wrote:
> Hi John,
>
> Thanks for your reply. I studied your very comprehensive Thermal
> Management post you linked, it's very good presentation of the laptop
> Linux thermal management *mess*. I'll use it as a guide line.
>
>> In your /sys/devices/virtual/thermal, what is the content of the type file
>> in each of the four cooling_device folders?  Is the content "fan" for one of
>> them (maybe "processor", "processor" and "LCD" for the others)?
> They are all "Fan", all 0-4 (5) of them. There's actually only one
> physical fan and "cooling devices" are actually fan speed bits, 0-4.
> So the real fan goes from 00000 to 11111 (0 to 31 dec).

That is an implementation I have not read about.  I wonder if it is 
particular to hwmon and/or thinkpad-acpi, or if ACPI handles it like 
that in general?  (My investigation didn't go much deeper on this front, 
since this laptop does not have an ACPI-supported fan to control.)

>
> What my daemon does, is simply to read cpu core temps from
> /sys/class/hwmon1 (this is coretemp module) and kicks of 5 bits above
> accordingly.

Interesting.  Lm-sensors was the only package I knew about that relied 
on hwmon.  So thinkpad-acpi does as well (assuming your script inherited 
that from thinkpad-acpi).  And about all I know about hwmon is that it 
is an extension of the sysfs that provides an alternate method of 
reading/controlling kernel parameters that may already be represented 
elsewhere under ACPI in the sysfs.  The purpose of hwmon might then be 
simply to support apps that explicitly rely on the hwmon locations.  I 
don't know for sure if it can add any kernel parameters not represented 
elsewhere in the sysfs, or perhaps present parameters as writable that 
are not writable as presented elsewhere.

>
> On 3.13 kernel, there seems to be no link between the
> /sys/class/hwmon1 (coretemp) and /sys/devices/virtual/thermal fans.
> Maybe thermald could be used to bind these together. I'll have to
> study this further on 3.15 kernel since obviously some fan control is
> happening there. Maybe I could use thermald to modify trip_points
> there.

You might also look at /sys/class/thermal and see what is 
represented/linked there.

I don't know if thermald supports control via the hwmon locations (or 
conversely, requires them).

But you might start by simply installing thermald and studying what 
happens.  Simply installing it is supposed to result in a default, 
zero-configuration mode of operation in which it attempts to keep the 
temperature under 45C.  There is a default hierarchy for how thermald 
applies the cooling devices, and I forget where the fan falls in that 
(it's in one of the linked references I supplied in the Lubuntu list 
post).  But just starting there might tell you some things, and then if 
you like you can dig into trying to figure out the manual configuration.

>
> Thanks for pointers,
>
> Tapio