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 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 } 124exit_up: 125 mutex_unlock(&data->update_lock); 126} 127 128static 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 151static 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 161static 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 */ 167static 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 i2c_set_clientdata(fake_client, NULL); 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); 208 209 /* Prevent 24RF08 corruption (in case of user error) */ 210 i2c_smbus_write_quick(real_client, 0); 211 212 if ((err = i2c_attach_client(real_client)) != 0) 213 goto exit_kfree2; 214 215 if ((err = i2c_attach_client(fake_client)) != 0) 216 goto exit_detach1; 217 218 err = sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr); 219 if (err) 220 goto exit_detach2; 221 222 return 0; 223 224exit_detach2: 225 i2c_detach_client(fake_client); 226exit_detach1: 227 i2c_detach_client(real_client); 228exit_kfree2: 229 kfree(fake_client); 230exit_kfree1: 231 kfree(data); 232 return err; 233} 234 235/* Will be called for both the real client and the fake client */ 236static int max6875_detach_client(struct i2c_client *client) 237{ 238 int err; 239 struct max6875_data *data = i2c_get_clientdata(client); 240 241 /* data is NULL for the fake client */ 242 if (data) 243 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); 244 245 err = i2c_detach_client(client); 246 if (err) 247 return err; 248 249 if (data) /* real client */ 250 kfree(data); 251 else /* fake client */ 252 kfree(client); 253 return 0; 254} 255 256static int __init max6875_init(void) 257{ 258 return i2c_add_driver(&max6875_driver); 259} 260 261static void __exit max6875_exit(void) 262{ 263 i2c_del_driver(&max6875_driver); 264} 265 266 267MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>"); 268MODULE_DESCRIPTION("MAX6875 driver"); 269MODULE_LICENSE("GPL"); 270 271module_init(max6875_init); 272module_exit(max6875_exit); 273