acerhdf - A kernelmodule which monitors the temperature 
          of the aspire one netbook, turns on/off the fan
          as soon as the upper/lower threshold is reached.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

0.0: VERY SHORT REFERENCE
   install: make && make install
   load module: modprobe acerhdf interval=10 fanon=67000 fanoff=62000 kernelmode=1
   read temperature: cat /sys/class/thermal/thermal_zone0/temp
   change parameter: echo 50000 > /sys/module/acerhdf/parameters/fanoff


1.0: INSTALL

1.1: DISTRIBUTION
   Ensure you've installed everything to build a kernelmodule. For debian you
   need at least to do: 'apt-get install build-essentials linux-kernel-headers'

1.2: ACERHDF
   Obtain the source of the latest version from http://piie.net/?section=acerhdf
   Untar the sources:  'tar xfvz acerhdf_kmod-<version>.tar.gz'
   Compile: 'cd acerhdf_kmod && make'
   Install: 'sudo make install'

1.3: AUTOSTART FAN CONTROL
   To automatically start the fan control you can do:
   'echo "options acerhdf kernelmode=1" | sudo tee /etc/modprobe.d/acerhdf.conf'


2.0: USAGE

2.1: LOADING THE MODULE
   To load the module into the kernel type: 'modprobe acerhdf'
   If you want let this happen automatically on system boot-up, add the module
   acerhdf to your list of autoloaded modules. (ask google how this works for
   your distribution)

2.2: CHECK
   Launch the command 'dmesg|grep acerhdf' and read the messages printed out.
   
2.3: READING THE TEMPERATURE
   The current temperature can be read by:
   'cat /sys/class/thermal/thermal_zone0/temp'

2.4: MONITORING / CONTROLLING THE FAN
   The fan can be monitored via: 
   'cat /sys/class/thermal/thermal_zone0/cdev0/cur_state'

   ATTENTION: setting the fan state manually can damage your hardware!
   To change the state manually you must first switch to user mode (see 2.5),
   then following commands will change the state:
   ON: 'echo 1 > /sys/class/thermal/thermal_zone0/cdev0/cur_state'
   OFF: 'echo 0 > /sys/class/thermal/thermal_zone0/cdev0/cur_state'
   
2.5: ENABLING / DISABLING THE FAN CONTROL
   enabled: acerhdf controls the fan automatically depending on the temperature
   and the temperature thresholds (see 2.6).
   disabled: acerhdf offers only the interface for reading the temperature and
   setting the state of the fan. A userspace program must take care about
   changing the fan state.

   You can switch on the fan control via:
   'echo enabled -n > /sys/class/thermal/thermal_zone0/mode'
   To switch the fan control off: 
   'echo disabled -n > /sys/class/thermal/thermal_zone0/mode'

2.6: CONFIGURATION / PARAMETERS
   acerhdf has following parameters:
   o interval=10 - The interval in seconds, in which the temperature should be
      checked in kernel mode. (default=10)
   o fanon=67000 - The temperature in Celsius above the fan should be switched on.
      (default=67000)
   o fanoff=62 - The temperature in Celsuis below the fan should be switched
      off. (default=62000)
   o verbose=0 - Print out verbose messages to dmesg. (default=0)
   o kernelmode=0 - enable the fan control after loading (default=0)
   o force_bios="" - For testing purposes, see below.

   Those parameters can be set when loading the module. E.g:
   'modprobe acerhdf interval=5 fanon=65000 fanoff=60000 kernelmode=1'
   You can add them to '/etc/modprobe.conf', so that they are automatically
   applied, when the module is loaded. The line in modprobe.conf can look like
   this:
   'options acerhdf interval=5 fanon=65000 fanoff=60000'

   Additionally every parameter (besides force_bios) can also be read and written 
   by accessing it via cat'ing or echo'ing the specific file in 
   /sys/module/acerhdf/parameters/*

   Example:
   'cat /sys/module/acerhdf/parameters/interval' to read the interval setting.
   'echo 50000 > /sys/module/acerhdf/parameters/fanoff' to change the fanoff
   setting.


3.0: TESTING UNSUPPORTED HARDWARE
      
      !!!! ATTENTION !!!!
   This could harm your hardware if you do not know what you are doing!
   
   If you have hardware / bios which isn't officially supported by acerhdf, but
   you are sure it should work, you can try to load the module by:
   'modprobe acerhdf force_bios="v0.3305"' or any other bios version defined in
   source of acerhdf. The force_bios parameter will cause acerhdf to omit the
   hardware and bios check and to pretend the chosen bios version is available.
   -> acerhdf will be started in user mode.
   Before switching to kernel mode (see 2.5) test if the temperature and the fan
   can be correctly accessed (see 2.4)

   IMPORTANT: if you get your hardware / bios working with this parameter,
   report it to peter (a) piie.net then it will get into the list of supported
   devices.