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1 | Kernel driver ltc4245 |
2 | ===================== | |
3 | ||
4 | Supported chips: | |
5 | * Linear Technology LTC4245 | |
6 | Prefix: 'ltc4245' | |
7 | Addresses scanned: 0x20-0x3f | |
8 | Datasheet: | |
9 | http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517 | |
10 | ||
11 | Author: Ira W. Snyder <iws@ovro.caltech.edu> | |
12 | ||
13 | ||
14 | Description | |
15 | ----------- | |
16 | ||
17 | The LTC4245 controller allows a board to be safely inserted and removed | |
18 | from a live backplane in multiple supply systems such as CompactPCI and | |
19 | PCI Express. | |
20 | ||
21 | ||
22 | Usage Notes | |
23 | ----------- | |
24 | ||
25 | This driver does not probe for LTC4245 devices, due to the fact that some | |
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26 | of the possible addresses are unfriendly to probing. You will have to |
27 | instantiate the devices explicitly. | |
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28 | |
29 | Example: the following will load the driver for an LTC4245 at address 0x23 | |
30 | on I2C bus #1: | |
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31 | $ modprobe ltc4245 |
32 | $ echo ltc4245 0x23 > /sys/bus/i2c/devices/i2c-1/new_device | |
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33 | |
34 | ||
35 | Sysfs entries | |
36 | ------------- | |
37 | ||
38 | The LTC4245 has built-in limits for over and under current warnings. This | |
39 | makes it very likely that the reference circuit will be used. | |
40 | ||
41 | This driver uses the values in the datasheet to change the register values | |
42 | into the values specified in the sysfs-interface document. The current readings | |
43 | rely on the sense resistors listed in Table 2: "Sense Resistor Values". | |
44 | ||
45 | in1_input 12v input voltage (mV) | |
46 | in2_input 5v input voltage (mV) | |
47 | in3_input 3v input voltage (mV) | |
48 | in4_input Vee (-12v) input voltage (mV) | |
49 | ||
50 | in1_min_alarm 12v input undervoltage alarm | |
51 | in2_min_alarm 5v input undervoltage alarm | |
52 | in3_min_alarm 3v input undervoltage alarm | |
53 | in4_min_alarm Vee (-12v) input undervoltage alarm | |
54 | ||
55 | curr1_input 12v current (mA) | |
56 | curr2_input 5v current (mA) | |
57 | curr3_input 3v current (mA) | |
58 | curr4_input Vee (-12v) current (mA) | |
59 | ||
60 | curr1_max_alarm 12v overcurrent alarm | |
61 | curr2_max_alarm 5v overcurrent alarm | |
62 | curr3_max_alarm 3v overcurrent alarm | |
63 | curr4_max_alarm Vee (-12v) overcurrent alarm | |
64 | ||
65 | in5_input 12v output voltage (mV) | |
66 | in6_input 5v output voltage (mV) | |
67 | in7_input 3v output voltage (mV) | |
68 | in8_input Vee (-12v) output voltage (mV) | |
69 | ||
70 | in5_min_alarm 12v output undervoltage alarm | |
71 | in6_min_alarm 5v output undervoltage alarm | |
72 | in7_min_alarm 3v output undervoltage alarm | |
73 | in8_min_alarm Vee (-12v) output undervoltage alarm | |
74 | ||
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75 | in9_input GPIO voltage data (see note 1) |
76 | in10_input GPIO voltage data (see note 1) | |
77 | in11_input GPIO voltage data (see note 1) | |
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78 | |
79 | power1_input 12v power usage (mW) | |
80 | power2_input 5v power usage (mW) | |
81 | power3_input 3v power usage (mW) | |
82 | power4_input Vee (-12v) power usage (mW) | |
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83 | |
84 | ||
85 | Note 1 | |
86 | ------ | |
87 | ||
88 | If you have NOT configured the driver to sample all GPIO pins as analog | |
89 | voltages, then the in10_input and in11_input sysfs attributes will not be | |
90 | created. The driver will sample the GPIO pin that is currently connected to the | |
91 | ADC as an analog voltage, and report the value in in9_input. | |
92 | ||
93 | If you have configured the driver to sample all GPIO pins as analog voltages, | |
94 | then they will be sampled in round-robin fashion. If userspace reads too | |
95 | slowly, -EAGAIN will be returned when you read the sysfs attribute containing | |
96 | the sensor reading. | |
97 | ||
98 | The LTC4245 chip can be configured to sample all GPIO pins with two methods: | |
8116e8dd | 99 | 1) platform data -- see include/linux/platform_data/ltc4245.h |
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100 | 2) OF device tree -- add the "ltc4245,use-extra-gpios" property to each chip |
101 | ||
102 | The default mode of operation is to sample a single GPIO pin. |