da74944d3a
Recently 'cur_state' user space 'sysfs' interface 'sysfs' has been deprecated. This interface is used in Nvidia systems for setting fan speed limit. Currently fan speed limit is set from the user space by setting 'sysfs' 'cur_state' attribute to 'max_state + n', where 'n' is required limit, for example: 15 for 50% speed limit, 20 for full fan speed enforcement. The purpose of this feature is to provides ability to limit fan speed according to some system wise considerations, like absence of some replaceable units (PSU or line cards), high system ambient temperature, unreliable transceivers temperature sensing or some other factors which indirectly impacts system's airflow. The motivation is to support fan low limit feature through 'hwmon' interface. Use 'hwmon' 'pwm' attribute for setting low limit for fan speed in case 'thermal' subsystem is configured in kernel. In this case setting fan speed through 'hwmon' will never let the 'thermal' subsystem to select a lower duty cycle than the duty cycle selected with the 'pwm' attribute. From other side, fan speed is to be updated in hardware through 'pwm' only in case the requested fan speed is above last speed set by 'thermal' subsystem, otherwise requested fan speed will be just stored with no PWM update. Signed-off-by: Vadim Pasternak <vadimp@nvidia.com> Link: https://lore.kernel.org/r/20220126141825.13545-1-vadimp@nvidia.com Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.