2 max6875.c - driver for MAX6874/MAX6875
4 Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
6 Based on i2c/chips/eeprom.c
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
14 This driver makes the user EEPROM available for read.
16 The registers & config EEPROM should be accessed via i2c-dev.
18 The MAX6875 ignores the lowest address bit, so each chip responds to
19 two addresses - 0x50/0x51 and 0x52/0x53.
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.
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.
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 <asm/semaphore.h>
36 /* Do not scan - the MAX6875 access method will write to some EEPROM chips */
37 static unsigned short normal_i2c[] = {I2C_CLIENT_END};
39 /* Insmod parameters */
40 I2C_CLIENT_INSMOD_1(max6875);
42 /* The MAX6875 can only read/write 16 bytes at a time */
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
51 /* MAX6875 commands */
52 #define MAX6875_CMD_BLK_READ 0x84
54 /* Each client has this additional data */
56 struct i2c_client client;
57 struct semaphore update_lock;
60 u8 data[USER_EEPROM_SIZE];
61 unsigned long last_updated[USER_EEPROM_SLICES];
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);
68 /* This is the driver that will be inserted */
69 static struct i2c_driver max6875_driver = {
72 .attach_adapter = max6875_attach_adapter,
73 .detach_client = max6875_detach_client,
76 static void max6875_update_slice(struct i2c_client *client, int slice)
78 struct max6875_data *data = i2c_get_clientdata(client);
82 if (slice >= USER_EEPROM_SLICES)
85 down(&data->update_lock);
87 buf = &data->data[slice << SLICE_BITS];
89 if (!(data->valid & (1 << slice)) ||
90 time_after(jiffies, data->last_updated[slice])) {
92 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
94 data->valid &= ~(1 << slice);
96 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
98 /* select the eeprom address */
99 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
100 dev_err(&client->dev, "address set failed\n");
104 if (i2c_check_functionality(client->adapter,
105 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
106 if (i2c_smbus_read_i2c_block_data(client,
107 MAX6875_CMD_BLK_READ,
108 buf) != SLICE_SIZE) {
112 for (i = 0; i < SLICE_SIZE; i++) {
113 j = i2c_smbus_read_byte(client);
120 data->last_updated[slice] = jiffies;
121 data->valid |= (1 << slice);
124 up(&data->update_lock);
127 static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
130 struct i2c_client *client = kobj_to_i2c_client(kobj);
131 struct max6875_data *data = i2c_get_clientdata(client);
132 int slice, max_slice;
134 if (off > USER_EEPROM_SIZE)
137 if (off + count > USER_EEPROM_SIZE)
138 count = USER_EEPROM_SIZE - off;
140 /* refresh slices which contain requested bytes */
141 max_slice = (off + count - 1) >> SLICE_BITS;
142 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
143 max6875_update_slice(client, slice);
145 memcpy(buf, &data->data[off], count);
150 static struct bin_attribute user_eeprom_attr = {
154 .owner = THIS_MODULE,
156 .size = USER_EEPROM_SIZE,
157 .read = max6875_read,
160 static int max6875_attach_adapter(struct i2c_adapter *adapter)
162 return i2c_probe(adapter, &addr_data, max6875_detect);
165 /* This function is called by i2c_probe */
166 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
168 struct i2c_client *real_client;
169 struct i2c_client *fake_client;
170 struct max6875_data *data;
173 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
174 | I2C_FUNC_SMBUS_READ_BYTE))
177 /* Only check even addresses */
181 if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
184 /* A fake client is created on the odd address */
185 if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
190 /* Init real i2c_client */
191 real_client = &data->client;
192 i2c_set_clientdata(real_client, data);
193 real_client->addr = address;
194 real_client->adapter = adapter;
195 real_client->driver = &max6875_driver;
196 real_client->flags = 0;
197 strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
198 init_MUTEX(&data->update_lock);
200 /* Init fake client data */
201 /* set the client data to the i2c_client so that it will get freed */
202 i2c_set_clientdata(fake_client, fake_client);
203 fake_client->addr = address | 1;
204 fake_client->adapter = adapter;
205 fake_client->driver = &max6875_driver;
206 fake_client->flags = 0;
207 strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
209 /* Prevent 24RF08 corruption (in case of user error) */
210 i2c_smbus_write_quick(real_client, 0);
212 if ((err = i2c_attach_client(real_client)) != 0)
215 if ((err = i2c_attach_client(fake_client)) != 0)
218 sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
223 i2c_detach_client(real_client);
231 static int max6875_detach_client(struct i2c_client *client)
235 err = i2c_detach_client(client);
238 kfree(i2c_get_clientdata(client));
242 static int __init max6875_init(void)
244 return i2c_add_driver(&max6875_driver);
247 static void __exit max6875_exit(void)
249 i2c_del_driver(&max6875_driver);
253 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
254 MODULE_DESCRIPTION("MAX6875 driver");
255 MODULE_LICENSE("GPL");
257 module_init(max6875_init);
258 module_exit(max6875_exit);