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1 | /* |
2 | * mcp3021.c - driver for the Microchip MCP3021 chip |
3 | * |
4 | * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc. |
5 | * Author: Mingkai Hu <Mingkai.hu@freescale.com> |
6 | * |
7 | * This driver export the value of analog input voltage to sysfs, the |
8 | * voltage unit is mV. Through the sysfs interface, lm-sensors tool |
9 | * can also display the input voltage. |
10 | * |
11 | * This program is free software; you can redistribute it and/or modify |
12 | * it under the terms of the GNU General Public License as published by |
13 | * the Free Software Foundation; either version 2 of the License, or |
14 | * (at your option) any later version. |
15 | */ |
16 | |
17 | #include <linux/kernel.h> |
18 | #include <linux/module.h> |
19 | #include <linux/hwmon.h> |
20 | #include <linux/slab.h> |
21 | #include <linux/i2c.h> |
22 | #include <linux/err.h> |
23 | #include <linux/device.h> |
24 | |
25 | /* Vdd info */ |
26 | #define MCP3021_VDD_MAX 5500 |
27 | #define MCP3021_VDD_MIN 2700 |
28 | #define MCP3021_VDD_REF 3300 |
29 | |
30 | /* output format */ |
31 | #define MCP3021_SAR_SHIFT 2 |
32 | #define MCP3021_SAR_MASK 0x3ff |
33 | |
34 | #define MCP3021_OUTPUT_RES 10 /* 10-bit resolution */ |
35 | #define MCP3021_OUTPUT_SCALE 4 |
36 | |
37 | /* |
38 | * Client data (each client gets its own) |
39 | */ |
40 | struct mcp3021_data { |
41 | struct device *hwmon_dev; |
42 | u32 vdd; /* device power supply */ |
43 | }; |
44 | |
45 | static int mcp3021_read16(struct i2c_client *client) |
46 | { |
47 | int ret; |
48 | u16 reg; |
49 | __be16 buf; |
50 | |
51 | ret = i2c_master_recv(client, (char *)&buf, 2); |
52 | if (ret < 0) |
53 | return ret; |
54 | if (ret != 2) |
55 | return -EIO; |
56 | |
57 | /* The output code of the MCP3021 is transmitted with MSB first. */ |
58 | reg = be16_to_cpu(buf); |
59 | |
60 | /* |
61 | * The ten-bit output code is composed of the lower 4-bit of the |
62 | * first byte and the upper 6-bit of the second byte. |
63 | */ |
64 | reg = (reg >> MCP3021_SAR_SHIFT) & MCP3021_SAR_MASK; |
65 | |
66 | return reg; |
67 | } |
68 | |
69 | static inline u16 volts_from_reg(u16 vdd, u16 val) |
70 | { |
71 | if (val == 0) |
72 | return 0; |
73 | |
74 | val = val * MCP3021_OUTPUT_SCALE - MCP3021_OUTPUT_SCALE / 2; |
75 | |
76 | return val * DIV_ROUND_CLOSEST(vdd, |
77 | (1 << MCP3021_OUTPUT_RES) * MCP3021_OUTPUT_SCALE); |
78 | } |
79 | |
80 | static ssize_t show_in_input(struct device *dev, struct device_attribute *attr, |
81 | char *buf) |
82 | { |
83 | struct i2c_client *client = to_i2c_client(dev); |
84 | struct mcp3021_data *data = i2c_get_clientdata(client); |
85 | int reg, in_input; |
86 | |
87 | reg = mcp3021_read16(client); |
88 | if (reg < 0) |
89 | return reg; |
90 | |
91 | in_input = volts_from_reg(data->vdd, reg); |
92 | return sprintf(buf, "%d\n", in_input); |
93 | } |
94 | |
95 | static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL); |
96 | |
97 | static int mcp3021_probe(struct i2c_client *client, |
98 | const struct i2c_device_id *id) |
99 | { |
100 | int err; |
101 | struct mcp3021_data *data = NULL; |
102 | |
103 | if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) |
104 | return -ENODEV; |
105 | |
106 | data = kzalloc(sizeof(struct mcp3021_data), GFP_KERNEL); |
107 | if (!data) |
108 | return -ENOMEM; |
109 | |
110 | i2c_set_clientdata(client, data); |
111 | |
112 | if (client->dev.platform_data) { |
113 | data->vdd = *(u32 *)client->dev.platform_data; |
114 | if (data->vdd > MCP3021_VDD_MAX || |
115 | data->vdd < MCP3021_VDD_MIN) { |
116 | err = -EINVAL; |
117 | goto exit_free; |
118 | } |
119 | } else |
120 | data->vdd = MCP3021_VDD_REF; |
121 | |
122 | err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr); |
123 | if (err) |
124 | goto exit_free; |
125 | |
126 | data->hwmon_dev = hwmon_device_register(&client->dev); |
127 | if (IS_ERR(data->hwmon_dev)) { |
128 | err = PTR_ERR(data->hwmon_dev); |
129 | goto exit_remove; |
130 | } |
131 | |
132 | return 0; |
133 | |
134 | exit_remove: |
135 | sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr); |
136 | exit_free: |
137 | kfree(data); |
138 | return err; |
139 | } |
140 | |
141 | static int mcp3021_remove(struct i2c_client *client) |
142 | { |
143 | struct mcp3021_data *data = i2c_get_clientdata(client); |
144 | |
145 | hwmon_device_unregister(data->hwmon_dev); |
146 | sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr); |
147 | kfree(data); |
148 | |
149 | return 0; |
150 | } |
151 | |
152 | static const struct i2c_device_id mcp3021_id[] = { |
153 | { "mcp3021", 0 }, |
154 | { } |
155 | }; |
156 | MODULE_DEVICE_TABLE(i2c, mcp3021_id); |
157 | |
158 | static struct i2c_driver mcp3021_driver = { |
159 | .driver = { |
160 | .name = "mcp3021", |
161 | }, |
162 | .probe = mcp3021_probe, |
163 | .remove = mcp3021_remove, |
164 | .id_table = mcp3021_id, |
165 | }; |
166 | |
167 | module_i2c_driver(mcp3021_driver); |
168 | |
169 | MODULE_AUTHOR("Mingkai Hu <Mingkai.hu@freescale.com>"); |
170 | MODULE_DESCRIPTION("Microchip MCP3021 driver"); |
171 | MODULE_LICENSE("GPL"); |
172 |
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