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 */
37 static unsigned short normal_i2c[] = {I2C_CLIENT_END};
38
39 /* Insmod parameters */
40 I2C_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 */
55 struct 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
64 static int max6875_attach_adapter(struct i2c_adapter *adapter);
65 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
66 static int max6875_detach_client(struct i2c_client *client);
67
68 /* This is the driver that will be inserted */
69 static 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
77 static 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 buf) != SLICE_SIZE) {
110 goto exit_up;
111 }
112 } else {
113 for (i = 0; i < SLICE_SIZE; i++) {
114 j = i2c_smbus_read_byte(client);
115 if (j < 0) {
116 goto exit_up;
117 }
118 buf[i] = j;
119 }
120 }
121 data->last_updated[slice] = jiffies;
122 data->valid |= (1 << slice);
123 }
124 exit_up:
125 mutex_unlock(&data->update_lock);
126 }
127
128 static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
129 size_t count)
130 {
131 struct i2c_client *client = kobj_to_i2c_client(kobj);
132 struct max6875_data *data = i2c_get_clientdata(client);
133 int slice, max_slice;
134
135 if (off > USER_EEPROM_SIZE)
136 return 0;
137
138 if (off + count > USER_EEPROM_SIZE)
139 count = USER_EEPROM_SIZE - off;
140
141 /* refresh slices which contain requested bytes */
142 max_slice = (off + count - 1) >> SLICE_BITS;
143 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
144 max6875_update_slice(client, slice);
145
146 memcpy(buf, &data->data[off], count);
147
148 return count;
149 }
150
151 static struct bin_attribute user_eeprom_attr = {
152 .attr = {
153 .name = "eeprom",
154 .mode = S_IRUGO,
155 .owner = THIS_MODULE,
156 },
157 .size = USER_EEPROM_SIZE,
158 .read = max6875_read,
159 };
160
161 static int max6875_attach_adapter(struct i2c_adapter *adapter)
162 {
163 return i2c_probe(adapter, &addr_data, max6875_detect);
164 }
165
166 /* This function is called by i2c_probe */
167 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
168 {
169 struct i2c_client *real_client;
170 struct i2c_client *fake_client;
171 struct max6875_data *data;
172 int err = 0;
173
174 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
175 | I2C_FUNC_SMBUS_READ_BYTE))
176 return 0;
177
178 /* Only check even addresses */
179 if (address & 1)
180 return 0;
181
182 if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
183 return -ENOMEM;
184
185 /* A fake client is created on the odd address */
186 if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
187 err = -ENOMEM;
188 goto exit_kfree1;
189 }
190
191 /* Init real i2c_client */
192 real_client = &data->client;
193 i2c_set_clientdata(real_client, data);
194 real_client->addr = address;
195 real_client->adapter = adapter;
196 real_client->driver = &max6875_driver;
197 real_client->flags = 0;
198 strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
199 mutex_init(&data->update_lock);
200
201 /* Init fake client data */
202 /* set the client data to the i2c_client so that it will get freed */
203 i2c_set_clientdata(fake_client, fake_client);
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_detach;
218
219 sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
220
221 return 0;
222
223 exit_detach:
224 i2c_detach_client(real_client);
225 exit_kfree2:
226 kfree(fake_client);
227 exit_kfree1:
228 kfree(data);
229 return err;
230 }
231
232 static int max6875_detach_client(struct i2c_client *client)
233 {
234 int err;
235
236 err = i2c_detach_client(client);
237 if (err)
238 return err;
239 kfree(i2c_get_clientdata(client));
240 return 0;
241 }
242
243 static int __init max6875_init(void)
244 {
245 return i2c_add_driver(&max6875_driver);
246 }
247
248 static void __exit max6875_exit(void)
249 {
250 i2c_del_driver(&max6875_driver);
251 }
252
253
254 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
255 MODULE_DESCRIPTION("MAX6875 driver");
256 MODULE_LICENSE("GPL");
257
258 module_init(max6875_init);
259 module_exit(max6875_exit);
260
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