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1Kernel driver via686a
2=====================
3
4Supported chips:
5 * Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor
6 Prefix: 'via686a'
7 Addresses scanned: ISA in PCI-space encoded address
8 Datasheet: On request through web form (http://www.via.com.tw/en/support/datasheets/)
9
10Authors:
11 Kyösti Mälkki <kmalkki@cc.hut.fi>,
12 Mark D. Studebaker <mdsxyz123@yahoo.com>
13 Bob Dougherty <bobd@stanford.edu>
14 (Some conversion-factor data were contributed by
15 Jonathan Teh Soon Yew <j.teh@iname.com>
16 and Alex van Kaam <darkside@chello.nl>.)
17
18Module Parameters
19-----------------
20
21force_addr=0xaddr Set the I/O base address. Useful for Asus A7V boards
22 that don't set the address in the BIOS. Does not do a
23 PCI force; the via686a must still be present in lspci.
24 Don't use this unless the driver complains that the
25 base address is not set.
26 Example: 'modprobe via686a force_addr=0x6000'
27
28Description
29-----------
30
31The driver does not distinguish between the chips and reports
32all as a 686A.
33
34The Via 686a southbridge has integrated hardware monitor functionality.
35It also has an I2C bus, but this driver only supports the hardware monitor.
36For the I2C bus driver, see <file:Documentation/i2c/busses/i2c-viapro>
37
38The Via 686a implements three temperature sensors, two fan rotation speed
39sensors, five voltage sensors and alarms.
40
41Temperatures are measured in degrees Celsius. An alarm is triggered once
42when the Overtemperature Shutdown limit is crossed; it is triggered again
43as soon as it drops below the hysteresis value.
44
45Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
46triggered if the rotation speed has dropped below a programmable limit. Fan
47readings can be divided by a programmable divider (1, 2, 4 or 8) to give
48the readings more range or accuracy. Not all RPM values can accurately be
49represented, so some rounding is done. With a divider of 2, the lowest
50representable value is around 2600 RPM.
51
52Voltage sensors (also known as IN sensors) report their values in volts.
53An alarm is triggered if the voltage has crossed a programmable minimum
54or maximum limit. Voltages are internally scalled, so each voltage channel
55has a different resolution and range.
56
57If an alarm triggers, it will remain triggered until the hardware register
58is read at least once. This means that the cause for the alarm may
59already have disappeared! Note that in the current implementation, all
60hardware registers are read whenever any data is read (unless it is less
61than 1.5 seconds since the last update). This means that you can easily
62miss once-only alarms.
63
64The driver only updates its values each 1.5 seconds; reading it more often
65will do no harm, but will return 'old' values.