/**************************************************************************
 * thinkfan version 0.8 -- copyleft 09-2011, Victor Mataré
 *
 * thinkfan is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * thinkfan is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with thinkfan.  If not, see <http://www.gnu.org/licenses/>.
 **************************************************************************/

Thinkfan is a simple, lightweight fan control program. Originally designed
specifically for IBM/Lenovo Thinkpads, it now supports any kind of system via
the sysfs hwmon interface (/sys/class/hwmon). It is designed to eat as little
CPU power as possible.



Contents of this file
=====================

(0) WARNING

(1) How it works

(2) Install and configure
(2.1)  Build
(2.2a) Configure hardware interface (IBM/Lenovo Thinkpads)
(2.2b) Configure hardware interface (any system)
(2.3)  Configure fan behaviour
(2.4)  Test and install

(3) Usage
(3.1)  Invocation
(3.2)  Temperature biasing (the -b option)
(3.3)  Pulsing-fan workaround
(3.4)  Signals

(4) Contact/Bugs



(0) WARNING!!!!
===============

There's only very basic sanity checking on the configuration (semantic
plausibility). You can set the temperature limits as insane as you like.

Any change to fan behaviour that results in higher temperatures in some parts
of the system will shorten your system's lifetime and/or cause weird hardware
bugs that'll make you pull out your hair.

   No warranties whatsoever.

If this program steals your car, kills your horse, smokes your dope or pees
on your carpet...
 - too bad, you're on your own.



(1) How it works
================

Thinkfan sets your fan speed according to predefined temperature limits that
are specified in the config file. There are two modes of operation:


(1.1) Simple Mode
-----------------
In simple mode, thinkfan uses only the highest temperature it can find. This
was the only choice in versions before 0.8. However, it's potentially
dangerous for devices with a low temperature rating like hard drives. For
these devices, you should specify a correction value that's added to the
actual temperature.


(1.2) Complex Mode
------------------
In complex mode, temperature limits are defined for each sensor individually.
If *at least one* upper limit is reached we switch to the next fan level, and
if *all* lower limits are reached, we switch to the previous level.
This is a new feature in 0.8. It allows very fine-grained control and is the
preferred way of using thinkfan. However it may require a bit of tweaking and
experimentation to get a suitable config for your system.



(2) How to install
==================

(2.1) Build
-----------
Run
# make CFLAGS="-O3"
To build a fully optimized executable.

If you want to debug:
# make CFLAGS="-g3 -O0"
But remember you have to "make clean" before rebuilding in the same directory.


(2.2) Configure
---------------
The default config file location is /etc/thinkfan.conf. You should start with
one of the supplied example configs and tweak from there. There are two
different hardware interfaces:

a) /proc/acpi/ibm/ (default)
   Most IBM/Lenovo Thinkpads and some other Lenovo models support this. You
   need the thinkpad_acpi kernel driver (see below).

b) /sys/class/hwmon/
   This is a generic interface which is not hardware-specific. You need an
   hwmon-driver for your system that allows reading temperatures and
   controlling the fan from userspace.


(2.2a) Configure hardware interface (IBM/Lenovo Thinkpads)
--------------------------------------------------------------
First, you need to load the thinkpad_acpi module with fan_control=1:
# modprobe thinkpad_acpi fan_control=1
See your distribution documentation for how to load modules at bootup with
custom options.

Then you might want to check out which fan levels your fan controller
supports by doing something like this:

for i in 0 1 2 3 4 5 6 7; do
	echo "level $i" > /proc/acpi/ibm/fan
	echo "level $i..."
	sleep 6
	cat /proc/acpi/ibm/fan | egrep "^speed"
	echo
done
echo "level auto" > /proc/acpi/ibm/fan

Now you have to choose whether you want to use complex or simple temperature
limits. I recommend using complex limits, since that gives you more control.
Whatever you choose, you should have two lines saying

 sensor /proc/acpi/ibm/thermal
 fan /proc/acpi/ibm/fan

in your config. /proc/acpi/ibm/thermal provides 8 or 16 temperatures, so if
you use complex temperature limits, your limits need have that same length.


(2.2b) Configure hardware interface (any system)
-------------------------------------------------------
On all systems other than IBM/Lenovo Thinkpads, you need to provide thinkfan
with the path(s) of all sysfs temperature sensor files you want to use. You
may find them by doing something like this:
# find -L /sys/class/hwmon -maxdepth 5 -name "temp*_input" \
       -print -exec cat \{\} \; 2>/dev/null

Now put all file names into the config file that give you a sensible
temperature reading, each one on a separate "sensor" line. Example:
sensor /sys/class/hwmon/hwmon3/device/temp10_input
...

Next you need to find the PWM control file of your fan:
# find -L /sys/class/hwmon -maxdepth 3 -name "pwm?" \
       -print -exec cat \{\} \; 2>/dev/null

At the moment, thinkfan can control only one fan. Support for multiple fans
may be added in a later release. Put your PWM control file on a "fan" line
like so:
fan /sys/class/hwmon/hwmon3/device/pwm1

You'll want to try out the behaviour of your PWM controller by echo'ing some
numbers from 0 to 255 to your PWM file and then checking the fan RPM in
fan?_input.

ATTENTION: Most hwmon drivers seem to disable userspace fan control after
suspend/resume. That means you'll have to send a SIGHUP to thinkfan after
resuming to make it restore userspace fan control. Check your distribution
documentation to find out how you can do a "pkill -HUP thinkfan" after
resuming.
By default, thinkfan re-initializes the PWM control *every time* a fan speed
is set. This is safe, but stupid. So if you want to do it properly, go the
SIGHUP way and use the -z option (see below).


(2.3) Configure fan behaviour
-----------------------------
Carefully edit the fan-config tuples to your needs. Note that for the sysfs
hwmon-interface, the fan level is a number from 0 to 255, while in the
IBM-Interface, it's a number from 0 to 7. You also have the option of using
strings like "level 0", "level auto" or "level disengaged" (WITH the
quotation marks). In DANGEROUS mode, you can even use arbitrary (unknown)
garbage as fan level.

The temperature limits for different fan levels should overlap, so that once
the fan is on, it keeps running for a while.

If using simple temperature limits, you should specify a correction value for
the temperature of your harddisk, because it's much more sensitive to high
temperatures than your CPU. If using /proc/acpi/ibm/thermal, take a look at
http://www.thinkwiki.org/wiki/Thermal_Sensors .
If you're using sysfs to read temperatures, you'll have to find out about the
meaning of your sensors on your own. A good starting point could be the
documentation of your hwmon driver.  Once you know which sensor belongs to
your harddrive, you should specify a correction value for it. For a sysfs
sensor, this would look like

 sensor /path/to/harddisk's/temp_input (15)

This will add 15°C to the temperature read from your harddisk and thus keep
it from heating up to the upper limit of your first fan level. In
/proc/acpi/ibm/thermal, the harddisk might be at the 3rd position:

 sensor /proc/acpi/ibm/thermal (0, 0, 15)

As this is just a quick-shot solution for the problem with overheating hard
disks, I really recommend using complex temperature limits. Go take a look at
thinkfan.conf.complex to learn about the syntax.


(2.4) Test and install
----------------------
Run ./thinkfan -n -c PATH_TO_CONFIG and watch it do its job. Try putting some
load on your system with glxgears or running some infinite loop in bash.  If
everything works nicely, forget about it for a while to make sure it's
stable.
Once you're confident that it works well for you, you may want to copy it to
/usr/local/sbin or whatever you like and run it without -n.



(3) USAGE
=========

(3.1) Invocation
----------------
Usage: thinkfan [-hnqzD] [-b BIAS ] [-c FILE] [-s SEC] [-p[SEC]]
-h       This help message
-s SEC   Maximum seconds between temperature updates (default: 5)
-b BIAS  Floating point number (0 ~ 20) to control rising edge
         temperature biasing strength (see below). Default 5.0
-c FILE  Load different configuration file (default: /etc/thinkfan.conf)
-n       Do not become a daemon and log to terminal instead of syslog
-q       Be quiet (no status info on terminal)
-z       Assume we don't have to worry about resuming when using the sysfs
         interface. Saves CPU load.
-p[SEC]  Use the pulsing-fan workaround (for older Thinkpads). Takes an
         optional floating-point argument (0 ~ 10s) as depulsing duration.
         Defaults to 0.5s. See (3.3).
-D       DANGEROUS mode: No sanity checks on config! May damage your
         hardware!!


(3.2) Rising Temperature Exaggeration (the -b option)
-----------------------------------------------------
Thinkfan takes special measures to deal with temperatures rising very
suddenly (like when you turn on the computer and instantly run some
CPU/GPU-intensive app).

You can provide a floating point number between 0 and 20 to adjust the amount
of exaggeration. If the highest known temperature jumps up 2 °C or more, the
exaggeration is calculated to:
exaggeration = (sleeptime * (delta_t - 1)) * (0.1 * BIAS)
(BIAS is the value provided on the commandline)
This value is then added to the current highest temperature and the fan speed
decision is based on that.

Ex: If we slept for 5 seconds during the last cycle, provided a BIAS of 10
on the commandline, and the temperature increased by 3 °C, we get a bias of:
5*2*0.1*10 = 10 °C
That's pretty nervous. If you want to turn off biasing entirely, run
thinkfan with -b 0.

In addition to exaggerating the temperature reading, the sleep time is
reduced to 2 seconds, and then slowly increased back up to the specified
value.


(3.3) Pulsing-fan workaround (the -p option)
--------------------------------------------
Specifying this option activates the pulsing-fan workaround. It works by
setting the fan controller to "disengaged" mode for a short amount of time on
every cycle (check the -s option). The optional argument of the -p option is
the duration for which the fan is kept in "disengaged" mode (defaults to 0.5
seconds). Note that the time spent in "disengaged" mode adds to the cycle
time, so with the -p option, the default sleep time is actually 5.5 seconds.

(3.4) Signals
-------------
Send a SIGHUP to make thinkfan reload its config file and reinitialize fan
control:
# kill -HUP $(</var/run/thinkfan.pid)

SIGINT and SIGTERM are caught to make for a clean exit.



(4) CONTACT / BUG REPORTS
=========================

If you have questions or a bug report, please try the help forum at sf.net:
http://sourceforge.net/projects/thinkfan/forums/forum/905019

You can also send a mail to my last name (without the accent!) AT lih DOT rwth
DASH aachen DOT de. Oh, by the way, all files are UTF-8, so upgrade your
system if it can't deal with that. And make me a coffee, please.

