drivers/i2c/chips/max6875.c

   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 */
  37 static const unsigned short normal_i2c[] = { I2C_CLIENT_END };
  38
  39 /* Insmod parameters */
  40 I2C_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 */
  55 struct max6875_data {
  56         struct i2c_client       *fake_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
  64 static void max6875_update_slice(struct i2c_client *client, int slice)
  65 {
  66         struct max6875_data *data = i2c_get_clientdata(client);
  67         int i, j, addr;
  68         u8 *buf;
  69
  70         if (slice >= USER_EEPROM_SLICES)
  71                 return;
  72
  73         mutex_lock(&data->update_lock);
  74
  75         buf = &data->data[slice << SLICE_BITS];
  76
  77         if (!(data->valid & (1 << slice)) ||
  78             time_after(jiffies, data->last_updated[slice])) {
  79
  80                 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
  81
  82                 data->valid &= ~(1 << slice);
  83
  84                 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
  85
  86                 /* select the eeprom address */
  87                 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
  88                         dev_err(&client->dev, "address set failed\n");
  89                         goto exit_up;
  90                 }
  91
  92                 if (i2c_check_functionality(client->adapter,
  93                                             I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  94                         if (i2c_smbus_read_i2c_block_data(client,
  95                                                           MAX6875_CMD_BLK_READ,
  96                                                           SLICE_SIZE,
  97                                                           buf) != SLICE_SIZE) {
  98                                 goto exit_up;
  99                         }
 100                 } else {
 101                         for (i = 0; i < SLICE_SIZE; i++) {
 102                                 j = i2c_smbus_read_byte(client);
 103                                 if (j < 0) {
 104                                         goto exit_up;
 105                                 }
 106                                 buf[i] = j;
 107                         }
 108                 }
 109                 data->last_updated[slice] = jiffies;
 110                 data->valid |= (1 << slice);
 111         }
 112 exit_up:
 113         mutex_unlock(&data->update_lock);
 114 }
 115
 116 static ssize_t max6875_read(struct kobject *kobj,
 117                             struct bin_attribute *bin_attr,
 118                             char *buf, loff_t off, size_t count)
 119 {
 120         struct i2c_client *client = kobj_to_i2c_client(kobj);
 121         struct max6875_data *data = i2c_get_clientdata(client);
 122         int slice, max_slice;
 123
 124         if (off > USER_EEPROM_SIZE)
 125                 return 0;
 126
 127         if (off + count > USER_EEPROM_SIZE)
 128                 count = USER_EEPROM_SIZE - off;
 129
 130         /* refresh slices which contain requested bytes */
 131         max_slice = (off + count - 1) >> SLICE_BITS;
 132         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 133                 max6875_update_slice(client, slice);
 134
 135         memcpy(buf, &data->data[off], count);
 136
 137         return count;
 138 }
 139
 140 static struct bin_attribute user_eeprom_attr = {
 141         .attr = {
 142                 .name = "eeprom",
 143                 .mode = S_IRUGO,
 144         },
 145         .size = USER_EEPROM_SIZE,
 146         .read = max6875_read,
 147 };
 148
 149 /* Return 0 if detection is successful, -ENODEV otherwise */
 150 static int max6875_detect(struct i2c_client *client, int kind,
 151                           struct i2c_board_info *info)
 152 {
 153         struct i2c_adapter *adapter = client->adapter;
 154
 155         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 156                                      | I2C_FUNC_SMBUS_READ_BYTE))
 157                 return -ENODEV;
 158
 159         /* Only check even addresses */
 160         if (client->addr & 1)
 161                 return -ENODEV;
 162
 163         strlcpy(info->type, "max6875", I2C_NAME_SIZE);
 164
 165         return 0;
 166 }
 167
 168 static int max6875_probe(struct i2c_client *client,
 169                          const struct i2c_device_id *id)
 170 {
 171         struct max6875_data *data;
 172         int err;
 173
 174         if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 175                 return -ENOMEM;
 176
 177         /* A fake client is created on the odd address */
 178         data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1);
 179         if (!data->fake_client) {
 180                 err = -ENOMEM;
 181                 goto exit_kfree;
 182         }
 183
 184         /* Init real i2c_client */
 185         i2c_set_clientdata(client, data);
 186         mutex_init(&data->update_lock);
 187
 188         err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
 189         if (err)
 190                 goto exit_remove_fake;
 191
 192         return 0;
 193
 194 exit_remove_fake:
 195         i2c_unregister_device(data->fake_client);
 196 exit_kfree:
 197         kfree(data);
 198         return err;
 199 }
 200
 201 static int max6875_remove(struct i2c_client *client)
 202 {
 203         struct max6875_data *data = i2c_get_clientdata(client);
 204
 205         i2c_unregister_device(data->fake_client);
 206
 207         sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
 208         kfree(data);
 209
 210         return 0;
 211 }
 212
 213 static const struct i2c_device_id max6875_id[] = {
 214         { "max6875", 0 },
 215         { }
 216 };
 217
 218 static struct i2c_driver max6875_driver = {
 219         .driver = {
 220                 .name   = "max6875",
 221         },
 222         .probe          = max6875_probe,
 223         .remove         = max6875_remove,
 224         .id_table       = max6875_id,
 225
 226         .detect         = max6875_detect,
 227         .address_data   = &addr_data,
 228 };
 229
 230 static int __init max6875_init(void)
 231 {
 232         return i2c_add_driver(&max6875_driver);
 233 }
 234
 235 static void __exit max6875_exit(void)
 236 {
 237         i2c_del_driver(&max6875_driver);
 238 }
 239
 240
 241 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 242 MODULE_DESCRIPTION("MAX6875 driver");
 243 MODULE_LICENSE("GPL");
 244
 245 module_init(max6875_init);
 246 module_exit(max6875_exit);