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/module.h> 31 #include <linux/slab.h> 32 #include <linux/i2c.h> 33 #include <linux/mutex.h> 34 35 /* The MAX6875 can only read/write 16 bytes at a time */ 36 #define SLICE_SIZE 16 37 #define SLICE_BITS 4 38 39 /* USER EEPROM is at addresses 0x8100 - 0x82FF */ 40 #define USER_EEPROM_BASE 0x8100 41 #define USER_EEPROM_SIZE 0x0200 42 #define USER_EEPROM_SLICES 32 43 44 /* MAX6875 commands */ 45 #define MAX6875_CMD_BLK_READ 0x84 46 47 /* Each client has this additional data */ 48 struct max6875_data { 49 struct i2c_client *fake_client; 50 struct mutex update_lock; 51 52 u32 valid; 53 u8 data[USER_EEPROM_SIZE]; 54 unsigned long last_updated[USER_EEPROM_SLICES]; 55 }; 56 57 static void max6875_update_slice(struct i2c_client *client, int slice) 58 { 59 struct max6875_data *data = i2c_get_clientdata(client); 60 int i, j, addr; 61 u8 *buf; 62 63 if (slice >= USER_EEPROM_SLICES) 64 return; 65 66 mutex_lock(&data->update_lock); 67 68 buf = &data->data[slice << SLICE_BITS]; 69 70 if (!(data->valid & (1 << slice)) || 71 time_after(jiffies, data->last_updated[slice])) { 72 73 dev_dbg(&client->dev, "Starting update of slice %u\n", slice); 74 75 data->valid &= ~(1 << slice); 76 77 addr = USER_EEPROM_BASE + (slice << SLICE_BITS); 78 79 /* select the eeprom address */ 80 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) { 81 dev_err(&client->dev, "address set failed\n"); 82 goto exit_up; 83 } 84 85 if (i2c_check_functionality(client->adapter, 86 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { 87 if (i2c_smbus_read_i2c_block_data(client, 88 MAX6875_CMD_BLK_READ, 89 SLICE_SIZE, 90 buf) != SLICE_SIZE) { 91 goto exit_up; 92 } 93 } else { 94 for (i = 0; i < SLICE_SIZE; i++) { 95 j = i2c_smbus_read_byte(client); 96 if (j < 0) { 97 goto exit_up; 98 } 99 buf[i] = j; 100 } 101 } 102 data->last_updated[slice] = jiffies; 103 data->valid |= (1 << slice); 104 } 105 exit_up: 106 mutex_unlock(&data->update_lock); 107 } 108 109 static ssize_t max6875_read(struct file *filp, struct kobject *kobj, 110 struct bin_attribute *bin_attr, 111 char *buf, loff_t off, size_t count) 112 { 113 struct i2c_client *client = kobj_to_i2c_client(kobj); 114 struct max6875_data *data = i2c_get_clientdata(client); 115 int slice, max_slice; 116 117 /* refresh slices which contain requested bytes */ 118 max_slice = (off + count - 1) >> SLICE_BITS; 119 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++) 120 max6875_update_slice(client, slice); 121 122 memcpy(buf, &data->data[off], count); 123 124 return count; 125 } 126 127 static struct bin_attribute user_eeprom_attr = { 128 .attr = { 129 .name = "eeprom", 130 .mode = S_IRUGO, 131 }, 132 .size = USER_EEPROM_SIZE, 133 .read = max6875_read, 134 }; 135 136 static int max6875_probe(struct i2c_client *client, 137 const struct i2c_device_id *id) 138 { 139 struct i2c_adapter *adapter = client->adapter; 140 struct max6875_data *data; 141 int err; 142 143 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA 144 | I2C_FUNC_SMBUS_READ_BYTE)) 145 return -ENODEV; 146 147 /* Only bind to even addresses */ 148 if (client->addr & 1) 149 return -ENODEV; 150 151 if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL))) 152 return -ENOMEM; 153 154 /* A fake client is created on the odd address */ 155 data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1); 156 if (!data->fake_client) { 157 err = -ENOMEM; 158 goto exit_kfree; 159 } 160 161 /* Init real i2c_client */ 162 i2c_set_clientdata(client, data); 163 mutex_init(&data->update_lock); 164 165 err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); 166 if (err) 167 goto exit_remove_fake; 168 169 return 0; 170 171 exit_remove_fake: 172 i2c_unregister_device(data->fake_client); 173 exit_kfree: 174 kfree(data); 175 return err; 176 } 177 178 static int max6875_remove(struct i2c_client *client) 179 { 180 struct max6875_data *data = i2c_get_clientdata(client); 181 182 i2c_unregister_device(data->fake_client); 183 184 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); 185 kfree(data); 186 187 return 0; 188 } 189 190 static const struct i2c_device_id max6875_id[] = { 191 { "max6875", 0 }, 192 { } 193 }; 194 MODULE_DEVICE_TABLE(i2c, max6875_id); 195 196 static struct i2c_driver max6875_driver = { 197 .driver = { 198 .name = "max6875", 199 }, 200 .probe = max6875_probe, 201 .remove = max6875_remove, 202 .id_table = max6875_id, 203 }; 204 205 module_i2c_driver(max6875_driver); 206 207 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>"); 208 MODULE_DESCRIPTION("MAX6875 driver"); 209 MODULE_LICENSE("GPL"); 210