Hi Daniel,
Am 09.01.25 um 22:36 schrieb Daniel Lezcano:
On 02/12/2024 15:52, Werner Sembach wrote:
Hi,
given a pair of a temperature sensor and a fan, I want to implement a driver.
that allows userspace to directly control the fan if it wants to. But have a
minimum fan speed when certain high temperatures are reached to avoid crashes
or hardware damage.
From the userspace, use directly the thermal-engine which is currently under
development [1]. You can add your platform specific code in a plugin while the
thermal engine will catch all the thermal events and pass them to it [2].
The thermal engine has a configuration file which will setup the thermal
framework to be woken up at different temperatures.
That still requires to trust userspace/the user to not write dangerous values
directly to sysfs?
The thermal engine will be proposed for a distro package, so the platform
support will be automatically supported.
Beside the trip points can be setup in the device to act on higher temperature.
As far as i can tell these trip points only notify userspace but you can't
attach code executed in kernel to it.
What is unclear is how the fan is managed. I suggest to have a look at
pwm-fan.c in drivers/hwmon
I already looked at hwmon, but that basically just writes trough values from and
to userspace and has no kernel side management of temperatures and fan speeds
whatsoever.
Kind regards,
Werner
e.g.
- temperature of target die is 80°C -> fan speed must be at least 30%
- temperature of target die is 90°C -> fan speed must be at least 40%
- temperature of target die is 105°C -> fan speed must be 100%
- temperature of target die is 110°C -> device shuts off to protect the hardware
Would the thermal subsystem be the right place for this to implement this
protection in driver?
It already has functions around periodic temperature polling and trip points.
[1] https://github.com/Linaro/libpm/tree/master
[2]
https://github.com/Linaro/libpm/blob/master/thermal-engine/plugins/te-plugin-example-game.c
