1 /* 2 * max6875.c - driver for MAX6874/MAX6875 3 * 4 * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com> 5 * 6 * Based on 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 /* The MAX6875 can only read/write 16 bytes at a time */ 37 #define SLICE_SIZE 16 38 #define SLICE_BITS 4 39 40 /* USER EEPROM is at addresses 0x8100 - 0x82FF */ 41 #define USER_EEPROM_BASE 0x8100 42 #define USER_EEPROM_SIZE 0x0200 43 #define USER_EEPROM_SLICES 32 44 45 /* MAX6875 commands */ 46 #define MAX6875_CMD_BLK_READ 0x84 47 48 /* Each client has this additional data */ 49 struct max6875_data { 50 struct i2c_client *fake_client; 51 struct mutex update_lock; 52 53 u32 valid; 54 u8 data[USER_EEPROM_SIZE]; 55 unsigned long last_updated[USER_EEPROM_SLICES]; 56 }; 57 58 static void max6875_update_slice(struct i2c_client *client, int slice) 59 { 60 struct max6875_data *data = i2c_get_clientdata(client); 61 int i, j, addr; 62 u8 *buf; 63 64 if (slice >= USER_EEPROM_SLICES) 65 return; 66 67 mutex_lock(&data->update_lock); 68 69 buf = &data->data[slice << SLICE_BITS]; 70 71 if (!(data->valid & (1 << slice)) || 72 time_after(jiffies, data->last_updated[slice])) { 73 74 dev_dbg(&client->dev, "Starting update of slice %u\n", slice); 75 76 data->valid &= ~(1 << slice); 77 78 addr = USER_EEPROM_BASE + (slice << SLICE_BITS); 79 80 /* select the eeprom address */ 81 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) { 82 dev_err(&client->dev, "address set failed\n"); 83 goto exit_up; 84 } 85 86 if (i2c_check_functionality(client->adapter, 87 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { 88 if (i2c_smbus_read_i2c_block_data(client, 89 MAX6875_CMD_BLK_READ, 90 SLICE_SIZE, 91 buf) != SLICE_SIZE) { 92 goto exit_up; 93 } 94 } else { 95 for (i = 0; i < SLICE_SIZE; i++) { 96 j = i2c_smbus_read_byte(client); 97 if (j < 0) { 98 goto exit_up; 99 } 100 buf[i] = j; 101 } 102 } 103 data->last_updated[slice] = jiffies; 104 data->valid |= (1 << slice); 105 } 106 exit_up: 107 mutex_unlock(&data->update_lock); 108 } 109 110 static ssize_t max6875_read(struct file *filp, struct kobject *kobj, 111 struct bin_attribute *bin_attr, 112 char *buf, loff_t off, size_t count) 113 { 114 struct i2c_client *client = kobj_to_i2c_client(kobj); 115 struct max6875_data *data = i2c_get_clientdata(client); 116 int slice, max_slice; 117 118 if (off > USER_EEPROM_SIZE) 119 return 0; 120 121 if (off + count > USER_EEPROM_SIZE) 122 count = USER_EEPROM_SIZE - off; 123 124 /* refresh slices which contain requested bytes */ 125 max_slice = (off + count - 1) >> SLICE_BITS; 126 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++) 127 max6875_update_slice(client, slice); 128 129 memcpy(buf, &data->data[off], count); 130 131 return count; 132 } 133 134 static struct bin_attribute user_eeprom_attr = { 135 .attr = { 136 .name = "eeprom", 137 .mode = S_IRUGO, 138 }, 139 .size = USER_EEPROM_SIZE, 140 .read = max6875_read, 141 }; 142 143 static int max6875_probe(struct i2c_client *client, 144 const struct i2c_device_id *id) 145 { 146 struct i2c_adapter *adapter = client->adapter; 147 struct max6875_data *data; 148 int err; 149 150 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA 151 | I2C_FUNC_SMBUS_READ_BYTE)) 152 return -ENODEV; 153 154 /* Only bind to even addresses */ 155 if (client->addr & 1) 156 return -ENODEV; 157 158 if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL))) 159 return -ENOMEM; 160 161 /* A fake client is created on the odd address */ 162 data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1); 163 if (!data->fake_client) { 164 err = -ENOMEM; 165 goto exit_kfree; 166 } 167 168 /* Init real i2c_client */ 169 i2c_set_clientdata(client, data); 170 mutex_init(&data->update_lock); 171 172 err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); 173 if (err) 174 goto exit_remove_fake; 175 176 return 0; 177 178 exit_remove_fake: 179 i2c_unregister_device(data->fake_client); 180 exit_kfree: 181 kfree(data); 182 return err; 183 } 184 185 static int max6875_remove(struct i2c_client *client) 186 { 187 struct max6875_data *data = i2c_get_clientdata(client); 188 189 i2c_unregister_device(data->fake_client); 190 191 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); 192 kfree(data); 193 194 return 0; 195 } 196 197 static const struct i2c_device_id max6875_id[] = { 198 { "max6875", 0 }, 199 { } 200 }; 201 202 static struct i2c_driver max6875_driver = { 203 .driver = { 204 .name = "max6875", 205 }, 206 .probe = max6875_probe, 207 .remove = max6875_remove, 208 .id_table = max6875_id, 209 }; 210 211 module_i2c_driver(max6875_driver); 212 213 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>"); 214 MODULE_DESCRIPTION("MAX6875 driver"); 215 MODULE_LICENSE("GPL"); 216