1Kernel driver gl518sm
2=====================
3
4Supported chips:
5
6  * Genesys Logic GL518SM release 0x00
7
8    Prefix: 'gl518sm'
9
10    Addresses scanned: I2C 0x2c and 0x2d
11
12  * Genesys Logic GL518SM release 0x80
13
14    Prefix: 'gl518sm'
15
16    Addresses scanned: I2C 0x2c and 0x2d
17
18    Datasheet: http://www.genesyslogic.com/
19
20Authors:
21       - Frodo Looijaard <frodol@dds.nl>,
22       - Kyösti Mälkki <kmalkki@cc.hut.fi>
23       - Hong-Gunn Chew <hglinux@gunnet.org>
24       - Jean Delvare <jdelvare@suse.de>
25
26Description
27-----------
28
29.. important::
30
31   For the revision 0x00 chip, the in0, in1, and in2  values (+5V, +3V,
32   and +12V) CANNOT be read. This is a limitation of the chip, not the driver.
33
34This driver supports the Genesys Logic GL518SM chip. There are at least
35two revision of this chip, which we call revision 0x00 and 0x80. Revision
360x80 chips support the reading of all voltages and revision 0x00 only
37for VIN3.
38
39The GL518SM implements one temperature sensor, two fan rotation speed
40sensors, and four voltage sensors. It can report alarms through the
41computer speakers.
42
43Temperatures are measured in degrees Celsius. An alarm goes off while the
44temperature is above the over temperature limit, and has not yet dropped
45below the hysteresis limit. The alarm always reflects the current
46situation. Measurements are guaranteed between -10 degrees and +110
47degrees, with a accuracy of +/-3 degrees.
48
49Rotation speeds are reported in RPM (rotations per minute). An alarm is
50triggered if the rotation speed has dropped below a programmable limit. In
51case when you have selected to turn fan1 off, no fan1 alarm is triggered.
52
53Fan readings can be divided by a programmable divider (1, 2, 4 or 8) to
54give the readings more range or accuracy.  Not all RPM values can
55accurately be represented, so some rounding is done. With a divider
56of 2, the lowest representable value is around 1900 RPM.
57
58Voltage sensors (also known as VIN sensors) report their values in volts.
59An alarm is triggered if the voltage has crossed a programmable minimum or
60maximum limit. Note that minimum in this case always means 'closest to
61zero'; this is important for negative voltage measurements. The VDD input
62measures voltages between 0.000 and 5.865 volt, with a resolution of 0.023
63volt. The other inputs measure voltages between 0.000 and 4.845 volt, with
64a resolution of 0.019 volt. Note that revision 0x00 chips do not support
65reading the current voltage of any input except for VIN3; limit setting and
66alarms work fine, though.
67
68When an alarm is triggered, you can be warned by a beeping signal through your
69computer speaker. It is possible to enable all beeping globally, or only the
70beeping for some alarms.
71
72If an alarm triggers, it will remain triggered until the hardware register
73is read at least once (except for temperature alarms). This means that the
74cause for the alarm may already have disappeared! Note that in the current
75implementation, all hardware registers are read whenever any data is read
76(unless it is less than 1.5 seconds since the last update). This means that
77you can easily miss once-only alarms.
78
79The GL518SM only updates its values each 1.5 seconds; reading it more often
80will do no harm, but will return 'old' values.
81