hwmon: (f71882fg) Add documentation

Kernel driver f71882fg

======================

Supported chips:

  * Fintek F71882FG and F71883FG

    Prefix: 'f71882fg'

    Addresses scanned: none, address read from Super I/O config space

    Datasheet: Available from the Fintek website

  * Fintek F71862FG and F71863FG

    Prefix: 'f71862fg'

    Addresses scanned: none, address read from Super I/O config space

    Datasheet: Available from the Fintek website

  * Fintek F8000

    Prefix: 'f8000'

    Addresses scanned: none, address read from Super I/O config space

    Datasheet: Not public

Author: Hans de Goede <hdegoede@redhat.com>

Description

-----------

Fintek F718xxFG/F8000 Super I/O chips include complete hardware monitoring

capabilities. They can monitor up to 9 voltages (3 for the F8000), 4 fans and

3 temperature sensors.

These chips also have fan controlling features, using either DC or PWM, in

three different modes (one manual, two automatic).

The driver assumes that no more than one chip is present, which seems

reasonable.

Monitoring

----------

The Voltage, Fan and Temperature Monitoring uses the standard sysfs

interface as documented in sysfs-interface, without any exceptions.

Fan Control

-----------

Both PWM (pulse-width modulation) and DC fan speed control methods are

supported. The right one to use depends on external circuitry on the

motherboard, so the driver assumes that the BIOS set the method

properly.

There are 2 modes to specify the speed of the fan, PWM duty cycle (or DC

voltage) mode, where 0-100% duty cycle (0-100% of 12V) is specified. And RPM

mode where the actual RPM of the fan (as measured) is controlled and the speed

gets specified as 0-100% of the fan#_full_speed file.

Since both modes work in a 0-100% (mapped to 0-255) scale, there isn't a

whole lot of a difference when modifying fan control settings. The only

important difference is that in RPM mode the 0-100% controls the fan speed

between 0-100% of fan#_full_speed. It is assumed that if the BIOS programs

RPM mode, it will also set fan#_full_speed properly, if it does not then

fan control will not work properly, unless you set a sane fan#_full_speed

value yourself.

Switching between these modes requires re-initializing a whole bunch of

registers, so the mode which the BIOS has set is kept. The mode is

printed when loading the driver.

Three different fan control modes are supported; the mode number is written

to the pwm#_enable file. Note that not all modes are supported on all

chips, and some modes may only be available in RPM / PWM mode on the F8000.

Writing an unsupported mode will result in an invalid parameter error.

* 1: Manual mode

  You ask for a specific PWM duty cycle / DC voltage or a specific % of

  fan#_full_speed by writing to the pwm# file. This mode is only

  available on the F8000 if the fan channel is in RPM mode.

* 2: Normal auto mode

  You can define a number of temperature/fan speed trip points, which % the

  fan should run at at this temp and which temp a fan should follow using the

  standard sysfs interface. The number and type of trip points is chip

  depended, see which files are available in sysfs.

  Fan/PWM channel 3 of the F8000 is always in this mode!

* 3: Thermostat mode (Only available on the F8000 when in duty cycle mode)

  The fan speed is regulated to keep the temp the fan is mapped to between

  temp#_auto_point2_temp and temp#_auto_point3_temp.

Both of the automatic modes require that pwm1 corresponds to fan1, pwm2 to

fan2 and pwm3 to fan3.

	  will be called f71805f.

config SENSORS_F71882FG

	tristate "Fintek F71882FG and F71883FG"

	tristate "Fintek F71862FG, F71882FG and F8000"

	depends on EXPERIMENTAL

	help

	  If you say yes here you get support for hardware monitoring

	  features of the Fintek F71882FG and F71883FG Super-I/O chips.

	  features of the Fintek F71882FG/F71883FG, F71862FG/71863FG

	  and F8000 Super-I/O chips.

	  This driver can also be built as a module.  If so, the module

	  will be called f71882fg.