[0/2] hwmon: Add new pwmX_fan_channel attribute

Message

Armin Wolf July 23, 2022, 3:38 a.m. UTC

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