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 <linux/i2c-sensor.h>
35 #include <asm/semaphore.h>
37 /* Do not scan - the MAX6875 access method will write to some EEPROM chips */
38 static unsigned short normal_i2c[] = {I2C_CLIENT_END};
39 static unsigned int normal_isa[] = {I2C_CLIENT_ISA_END};
41 /* Insmod parameters */
42 SENSORS_INSMOD_1(max6875);
44 /* The MAX6875 can only read/write 16 bytes at a time */
48 /* USER EEPROM is at addresses 0x8100 - 0x82FF */
49 #define USER_EEPROM_BASE 0x8100
50 #define USER_EEPROM_SIZE 0x0200
51 #define USER_EEPROM_SLICES 32
53 /* MAX6875 commands */
54 #define MAX6875_CMD_BLK_READ 0x84
56 /* Each client has this additional data */
58 struct i2c_client client;
59 struct semaphore update_lock;
62 u8 data[USER_EEPROM_SIZE];
63 unsigned long last_updated[USER_EEPROM_SLICES];
66 static int max6875_attach_adapter(struct i2c_adapter *adapter);
67 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
68 static int max6875_detach_client(struct i2c_client *client);
70 /* This is the driver that will be inserted */
71 static struct i2c_driver max6875_driver = {
74 .flags = I2C_DF_NOTIFY,
75 .attach_adapter = max6875_attach_adapter,
76 .detach_client = max6875_detach_client,
79 static void max6875_update_slice(struct i2c_client *client, int slice)
81 struct max6875_data *data = i2c_get_clientdata(client);
86 if (slice >= USER_EEPROM_SLICES)
89 down(&data->update_lock);
91 buf = &data->data[slice << SLICE_BITS];
93 if (!(data->valid & (1 << slice)) ||
94 time_after(jiffies, data->last_updated[slice])) {
96 dev_dbg(&client->dev, "Starting update of slice %u\n",
99 data->valid &= ~(1 << slice);
101 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
103 /* select the eeprom address */
104 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
105 dev_err(&client->dev, "address set failed\n");
110 if (i2c_check_functionality(client->adapter,
111 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
112 if (i2c_smbus_read_i2c_block_data(client,
113 MAX6875_CMD_BLK_READ,
114 buf) != SLICE_SIZE) {
119 for (i = 0; i < SLICE_SIZE; i++) {
120 j = i2c_smbus_read_byte(client);
128 data->last_updated[slice] = jiffies;
129 data->valid |= (1 << slice);
132 up(&data->update_lock);
135 static inline struct i2c_client *kobj_to_i2c_client(struct kobject *kobj)
137 return to_i2c_client(container_of(kobj, struct device, kobj));
140 static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
143 struct i2c_client *client = kobj_to_i2c_client(kobj);
144 struct max6875_data *data = i2c_get_clientdata(client);
145 int slice, max_slice;
147 if (off > USER_EEPROM_SIZE)
150 if (off + count > USER_EEPROM_SIZE)
151 count = USER_EEPROM_SIZE - off;
153 /* refresh slices which contain requested bytes */
154 max_slice = (off + count - 1) >> SLICE_BITS;
155 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
156 max6875_update_slice(client, slice);
158 memcpy(buf, &data->data[off], count);
163 static struct bin_attribute user_eeprom_attr = {
167 .owner = THIS_MODULE,
169 .size = USER_EEPROM_SIZE,
170 .read = max6875_read,
173 static int max6875_attach_adapter(struct i2c_adapter *adapter)
175 return i2c_detect(adapter, &addr_data, max6875_detect);
178 /* This function is called by i2c_detect */
179 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
181 struct i2c_client *real_client;
182 struct i2c_client *fake_client;
183 struct max6875_data *data;
186 /* Prevent 24rf08 corruption (in case of user error) */
188 i2c_smbus_xfer(adapter, address, 0, 0, 0,
189 I2C_SMBUS_QUICK, NULL);
191 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
192 | I2C_FUNC_SMBUS_READ_BYTE))
195 /* Only check even addresses */
199 if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL)))
201 memset(data, 0, sizeof(struct max6875_data));
203 /* A fake client is created on the odd address */
204 if (!(fake_client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
208 memset(fake_client, 0, sizeof(struct i2c_client));
210 /* Init real i2c_client */
211 real_client = &data->client;
212 i2c_set_clientdata(real_client, data);
213 real_client->addr = address;
214 real_client->adapter = adapter;
215 real_client->driver = &max6875_driver;
216 real_client->flags = 0;
217 strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
218 init_MUTEX(&data->update_lock);
220 /* Init fake client data */
221 /* set the client data to the i2c_client so that it will get freed */
222 i2c_set_clientdata(fake_client, fake_client);
223 fake_client->addr = address | 1;
224 fake_client->adapter = adapter;
225 fake_client->driver = &max6875_driver;
226 fake_client->flags = 0;
227 strlcpy(fake_client->name, "max6875-dummy", I2C_NAME_SIZE);
229 /* Prevent 24RF08 corruption (in case of user error) */
230 i2c_smbus_write_quick(real_client, 0);
232 if ((err = i2c_attach_client(real_client)) != 0)
235 if ((err = i2c_attach_client(fake_client)) != 0)
238 sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
243 i2c_detach_client(real_client);
251 static int max6875_detach_client(struct i2c_client *client)
255 err = i2c_detach_client(client);
257 dev_err(&client->dev, "i2c_detach_client() failed\n");
260 kfree(i2c_get_clientdata(client));
264 static int __init max6875_init(void)
266 return i2c_add_driver(&max6875_driver);
269 static void __exit max6875_exit(void)
271 i2c_del_driver(&max6875_driver);
275 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
276 MODULE_DESCRIPTION("MAX6875 driver");
277 MODULE_LICENSE("GPL");
279 module_init(max6875_init);
280 module_exit(max6875_exit);