Commit | Line | Data |
---|---|---|
7f15b664 M |
1 | Kernel driver lm87 |
2 | ================== | |
3 | ||
4 | Supported chips: | |
5 | * National Semiconductor LM87 | |
6 | Prefix: 'lm87' | |
c7fa3737 | 7 | Addresses scanned: I2C 0x2c - 0x2e |
7f15b664 | 8 | Datasheet: http://www.national.com/pf/LM/LM87.html |
c7fa3737 JD |
9 | * Analog Devices ADM1024 |
10 | Prefix: 'adm1024' | |
11 | Addresses scanned: I2C 0x2c - 0x2e | |
12 | Datasheet: http://www.analog.com/en/prod/0,2877,ADM1024,00.html | |
7f15b664 M |
13 | |
14 | Authors: | |
15 | Frodo Looijaard <frodol@dds.nl>, | |
16 | Philip Edelbrock <phil@netroedge.com>, | |
17 | Mark Studebaker <mdsxyz123@yahoo.com>, | |
18 | Stephen Rousset <stephen.rousset@rocketlogix.com>, | |
19 | Dan Eaton <dan.eaton@rocketlogix.com>, | |
7c81c60f | 20 | Jean Delvare <jdelvare@suse.de>, |
7f15b664 M |
21 | Original 2.6 port Jeff Oliver |
22 | ||
23 | Description | |
24 | ----------- | |
25 | ||
c7fa3737 JD |
26 | This driver implements support for the National Semiconductor LM87 |
27 | and the Analog Devices ADM1024. | |
7f15b664 M |
28 | |
29 | The LM87 implements up to three temperature sensors, up to two fan | |
30 | rotation speed sensors, up to seven voltage sensors, alarms, and some | |
c7fa3737 | 31 | miscellaneous stuff. The ADM1024 is fully compatible. |
7f15b664 M |
32 | |
33 | Temperatures are measured in degrees Celsius. Each input has a high | |
34 | and low alarm settings. A high limit produces an alarm when the value | |
35 | goes above it, and an alarm is also produced when the value goes below | |
36 | the low limit. | |
37 | ||
38 | Fan rotation speeds are reported in RPM (rotations per minute). An alarm is | |
39 | triggered if the rotation speed has dropped below a programmable limit. Fan | |
40 | readings can be divided by a programmable divider (1, 2, 4 or 8) to give | |
41 | the readings more range or accuracy. Not all RPM values can accurately be | |
42 | represented, so some rounding is done. With a divider of 2, the lowest | |
43 | representable value is around 2600 RPM. | |
44 | ||
45 | Voltage sensors (also known as IN sensors) report their values in | |
46 | volts. An alarm is triggered if the voltage has crossed a programmable | |
47 | minimum or maximum limit. Note that minimum in this case always means | |
48 | 'closest to zero'; this is important for negative voltage measurements. | |
49 | ||
50 | If an alarm triggers, it will remain triggered until the hardware register | |
51 | is read at least once. This means that the cause for the alarm may | |
52 | already have disappeared! Note that in the current implementation, all | |
53 | hardware registers are read whenever any data is read (unless it is less | |
54 | than 1.0 seconds since the last update). This means that you can easily | |
55 | miss once-only alarms. | |
56 | ||
57 | The lm87 driver only updates its values each 1.0 seconds; reading it more | |
58 | often will do no harm, but will return 'old' values. | |
59 | ||
60 | ||
61 | Hardware Configurations | |
62 | ----------------------- | |
63 | ||
64 | The LM87 has four pins which can serve one of two possible functions, | |
65 | depending on the hardware configuration. | |
66 | ||
67 | Some functions share pins, so not all functions are available at the same | |
47064d64 BH |
68 | time. Which are depends on the hardware setup. This driver normally |
69 | assumes that firmware configured the chip correctly. Where this is not | |
70 | the case, platform code must set the I2C client's platform_data to point | |
71 | to a u8 value to be written to the channel register. | |
7f15b664 M |
72 | |
73 | For reference, here is the list of exclusive functions: | |
74 | - in0+in5 (default) or temp3 | |
75 | - fan1 (default) or in6 | |
76 | - fan2 (default) or in7 | |
77 | - VID lines (default) or IRQ lines (not handled by this driver) |