1Kernel driver gl518sm
2=====================
3
4Supported chips:
5  * Genesys Logic GL518SM release 0x00
6    Prefix: 'gl518sm'
7    Addresses scanned: I2C 0x2c and 0x2d
8  * Genesys Logic GL518SM release 0x80
9    Prefix: 'gl518sm'
10    Addresses scanned: I2C 0x2c and 0x2d
11    Datasheet: http://www.genesyslogic.com/
12
13Authors:
14        Frodo Looijaard <frodol@dds.nl>,
15        Kyösti Mälkki <kmalkki@cc.hut.fi>
16        Hong-Gunn Chew <hglinux@gunnet.org>
17        Jean Delvare <jdelvare@suse.de>
18
19Description
20-----------
21
22IMPORTANT:
23
24For the revision 0x00 chip, the in0, in1, and in2  values (+5V, +3V,
25and +12V) CANNOT be read. This is a limitation of the chip, not the driver.
26
27This driver supports the Genesys Logic GL518SM chip. There are at least
28two revision of this chip, which we call revision 0x00 and 0x80. Revision
290x80 chips support the reading of all voltages and revision 0x00 only
30for VIN3.
31
32The GL518SM implements one temperature sensor, two fan rotation speed
33sensors, and four voltage sensors. It can report alarms through the
34computer speakers.
35
36Temperatures are measured in degrees Celsius. An alarm goes off while the
37temperature is above the over temperature limit, and has not yet dropped
38below the hysteresis limit. The alarm always reflects the current
39situation. Measurements are guaranteed between -10 degrees and +110
40degrees, with a accuracy of +/-3 degrees.
41
42Rotation speeds are reported in RPM (rotations per minute). An alarm is
43triggered if the rotation speed has dropped below a programmable limit. In
44case when you have selected to turn fan1 off, no fan1 alarm is triggered.
45
46Fan readings can be divided by a programmable divider (1, 2, 4 or 8) to
47give the readings more range or accuracy.  Not all RPM values can
48accurately be represented, so some rounding is done. With a divider
49of 2, the lowest representable value is around 1900 RPM.
50
51Voltage sensors (also known as VIN sensors) report their values in volts.
52An alarm is triggered if the voltage has crossed a programmable minimum or
53maximum limit. Note that minimum in this case always means 'closest to
54zero'; this is important for negative voltage measurements. The VDD input
55measures voltages between 0.000 and 5.865 volt, with a resolution of 0.023
56volt. The other inputs measure voltages between 0.000 and 4.845 volt, with
57a resolution of 0.019 volt. Note that revision 0x00 chips do not support
58reading the current voltage of any input except for VIN3; limit setting and
59alarms work fine, though.
60
61When an alarm is triggered, you can be warned by a beeping signal through your
62computer speaker. It is possible to enable all beeping globally, or only the
63beeping for some alarms.
64
65If an alarm triggers, it will remain triggered until the hardware register
66is read at least once (except for temperature alarms). This means that the
67cause for the alarm may already have disappeared! Note that in the current
68implementation, all hardware registers are read whenever any data is read
69(unless it is less than 1.5 seconds since the last update). This means that
70you can easily miss once-only alarms.
71
72The GL518SM only updates its values each 1.5 seconds; reading it more often
73will do no harm, but will return 'old' values.
74