Userspace software which needs to know which PWM channel is associated with which fan channel (like fancontrol/pwmconfig) currently has to probe each PWM channel and watch for fan speed changes. This process has multiple issues: 1. Hardware might overhead during probing of PWM channels. 2. Not all fans react the same to PWM changes, making detection unreliable. However some hwmon chips, especially firmware-based ones, already know which PWM channels are associated to which fan channel, making probing of them unnecessary. Add a new sysfs attribute to allow such chips to export this knowlege to userspace in a standardized manner. The first patch adds support for the new attribute to the hwmon core, while the second patch adds support for this new attribute to the dell-smm-hwmon driver. All changes have been tested on a Dell Inspiron 3505. Armin Wolf (2): hwmon: Add pwmX_fan_channel attribute hwmon: (dell-smm) Add support for pwmX_fan_channel attribute Documentation/ABI/testing/sysfs-class-hwmon | 8 ++++++++ Documentation/hwmon/dell-smm-hwmon.rst | 1 + Documentation/hwmon/sysfs-interface.rst | 3 +++ drivers/hwmon/dell-smm-hwmon.c | 15 ++++++++++++--- drivers/hwmon/hwmon.c | 1 + include/linux/hwmon.h | 2 ++ 6 files changed, 27 insertions(+), 3 deletions(-) -- 2.30.2
