tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 max6875.c - driver for MAX6874/MAX6875
3
4 Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
5
6 Based on i2c/chips/eeprom.c
7
8 The MAX6875 has a bank of registers and two banks of EEPROM.
9 Address ranges are defined as follows:
10 * 0x0000 - 0x0046 = configuration registers
11 * 0x8000 - 0x8046 = configuration EEPROM
12 * 0x8100 - 0x82FF = user EEPROM
13
14 This driver makes the user EEPROM available for read.
15
16 The registers & config EEPROM should be accessed via i2c-dev.
17
18 The MAX6875 ignores the lowest address bit, so each chip responds to
19 two addresses - 0x50/0x51 and 0x52/0x53.
20
21 Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
22 address, so this driver is destructive if loaded for the wrong EEPROM chip.
23
24 This program is free software; you can redistribute it and/or modify
25 it under the terms of the GNU General Public License as published by
26 the Free Software Foundation; version 2 of the License.
27*/
28
29#include <linux/kernel.h>
30#include <linux/init.h>
31#include <linux/module.h>
32#include <linux/slab.h>
33#include <linux/i2c.h>
34#include <linux/mutex.h>
35
36/* Do not scan - the MAX6875 access method will write to some EEPROM chips */
37static unsigned short normal_i2c[] = {I2C_CLIENT_END};
38
39/* Insmod parameters */
40I2C_CLIENT_INSMOD_1(max6875);
41
42/* The MAX6875 can only read/write 16 bytes at a time */
43#define SLICE_SIZE 16
44#define SLICE_BITS 4
45
46/* USER EEPROM is at addresses 0x8100 - 0x82FF */
47#define USER_EEPROM_BASE 0x8100
48#define USER_EEPROM_SIZE 0x0200
49#define USER_EEPROM_SLICES 32
50
51/* MAX6875 commands */
52#define MAX6875_CMD_BLK_READ 0x84
53
54/* Each client has this additional data */
55struct max6875_data {
56 struct i2c_client client;
57 struct mutex update_lock;
58
59 u32 valid;
60 u8 data[USER_EEPROM_SIZE];
61 unsigned long last_updated[USER_EEPROM_SLICES];
62};
63
64static int max6875_attach_adapter(struct i2c_adapter *adapter);
65static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
66static int max6875_detach_client(struct i2c_client *client);
67
68/* This is the driver that will be inserted */
69static struct i2c_driver max6875_driver = {
70 .driver = {
71 .name = "max6875",
72 },
73 .attach_adapter = max6875_attach_adapter,
74 .detach_client = max6875_detach_client,
75};
76
77static void max6875_update_slice(struct i2c_client *client, int slice)
78{
79 struct max6875_data *data = i2c_get_clientdata(client);
80 int i, j, addr;
81 u8 *buf;
82
83 if (slice >= USER_EEPROM_SLICES)
84 return;
85
86 mutex_lock(&data->update_lock);
87
88 buf = &data->data[slice << SLICE_BITS];
89
90 if (!(data->valid & (1 << slice)) ||
91 time_after(jiffies, data->last_updated[slice])) {
92
93 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
94
95 data->valid &= ~(1 << slice);
96
97 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
98
99 /* select the eeprom address */
100 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
101 dev_err(&client->dev, "address set failed\n");
102 goto exit_up;
103 }
104
105 if (i2c_check_functionality(client->adapter,
106 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
107 if (i2c_smbus_read_i2c_block_data(client,
108 MAX6875_CMD_BLK_READ,
109 SLICE_SIZE,
110 buf) != SLICE_SIZE) {
111 goto exit_up;
112 }
113 } else {
114 for (i = 0; i < SLICE_SIZE; i++) {
115 j = i2c_smbus_read_byte(client);
116 if (j < 0) {
117 goto exit_up;
118 }
119 buf[i] = j;
120 }
121 }
122 data->last_updated[slice] = jiffies;
123 data->valid |= (1 << slice);
124 }
125exit_up:
126 mutex_unlock(&data->update_lock);
127}
128
129static ssize_t max6875_read(struct kobject *kobj,
130 struct bin_attribute *bin_attr,
131 char *buf, loff_t off, size_t count)
132{
133 struct i2c_client *client = kobj_to_i2c_client(kobj);
134 struct max6875_data *data = i2c_get_clientdata(client);
135 int slice, max_slice;
136
137 if (off > USER_EEPROM_SIZE)
138 return 0;
139
140 if (off + count > USER_EEPROM_SIZE)
141 count = USER_EEPROM_SIZE - off;
142
143 /* refresh slices which contain requested bytes */
144 max_slice = (off + count - 1) >> SLICE_BITS;
145 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
146 max6875_update_slice(client, slice);
147
148 memcpy(buf, &data->data[off], count);
149
150 return count;
151}
152
153static struct bin_attribute user_eeprom_attr = {
154 .attr = {
155 .name = "eeprom",
156 .mode = S_IRUGO,
157 },
158 .size = USER_EEPROM_SIZE,
159 .read = max6875_read,
160};
161
162static int max6875_attach_adapter(struct i2c_adapter *adapter)
163{
164 return i2c_probe(adapter, &addr_data, max6875_detect);
165}
166
167/* This function is called by i2c_probe */
168static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
169{
170 struct i2c_client *real_client;
171 struct i2c_client *fake_client;
172 struct max6875_data *data;
173 int err = 0;
174
175 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
176 | I2C_FUNC_SMBUS_READ_BYTE))
177 return 0;
178
179 /* Only check even addresses */
180 if (address & 1)
181 return 0;
182
183 if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
184 return -ENOMEM;
185
186 /* A fake client is created on the odd address */
187 if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
188 err = -ENOMEM;
189 goto exit_kfree1;
190 }
191
192 /* Init real i2c_client */
193 real_client = &data->client;
194 i2c_set_clientdata(real_client, data);
195 real_client->addr = address;
196 real_client->adapter = adapter;
197 real_client->driver = &max6875_driver;
198 real_client->flags = 0;
199 strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
200 mutex_init(&data->update_lock);
201
202 /* Init fake client data */
203 i2c_set_clientdata(fake_client, NULL);
204 fake_client->addr = address | 1;
205 fake_client->adapter = adapter;
206 fake_client->driver = &max6875_driver;
207 fake_client->flags = 0;
208 strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
209
210 /* Prevent 24RF08 corruption (in case of user error) */
211 i2c_smbus_write_quick(real_client, 0);
212
213 if ((err = i2c_attach_client(real_client)) != 0)
214 goto exit_kfree2;
215
216 if ((err = i2c_attach_client(fake_client)) != 0)
217 goto exit_detach1;
218
219 err = sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
220 if (err)
221 goto exit_detach2;
222
223 return 0;
224
225exit_detach2:
226 i2c_detach_client(fake_client);
227exit_detach1:
228 i2c_detach_client(real_client);
229exit_kfree2:
230 kfree(fake_client);
231exit_kfree1:
232 kfree(data);
233 return err;
234}
235
236/* Will be called for both the real client and the fake client */
237static int max6875_detach_client(struct i2c_client *client)
238{
239 int err;
240 struct max6875_data *data = i2c_get_clientdata(client);
241
242 /* data is NULL for the fake client */
243 if (data)
244 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
245
246 err = i2c_detach_client(client);
247 if (err)
248 return err;
249
250 if (data) /* real client */
251 kfree(data);
252 else /* fake client */
253 kfree(client);
254 return 0;
255}
256
257static int __init max6875_init(void)
258{
259 return i2c_add_driver(&max6875_driver);
260}
261
262static void __exit max6875_exit(void)
263{
264 i2c_del_driver(&max6875_driver);
265}
266
267
268MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
269MODULE_DESCRIPTION("MAX6875 driver");
270MODULE_LICENSE("GPL");
271
272module_init(max6875_init);
273module_exit(max6875_exit);