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 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       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 int max6875_attach_adapter(struct i2c_adapter *adapter);
  65 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
  66 static int max6875_detach_client(struct i2c_client *client);
  67
  68 /* This is the driver that will be inserted */
  69 static 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
  77 static 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         }
 124 exit_up:
 125         mutex_unlock(&data->update_lock);
 126 }
 127
 128 static 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
 151 static struct bin_attribute user_eeprom_attr = {
 152         .attr = {
 153                 .name = "eeprom",
 154                 .mode = S_IRUGO,
 155         },
 156         .size = USER_EEPROM_SIZE,
 157         .read = max6875_read,
 158 };
 159
 160 static int max6875_attach_adapter(struct i2c_adapter *adapter)
 161 {
 162         return i2c_probe(adapter, &addr_data, max6875_detect);
 163 }
 164
 165 /* This function is called by i2c_probe */
 166 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
 167 {
 168         struct i2c_client *real_client;
 169         struct i2c_client *fake_client;
 170         struct max6875_data *data;
 171         int err = 0;
 172
 173         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 174                                      | I2C_FUNC_SMBUS_READ_BYTE))
 175                 return 0;
 176
 177         /* Only check even addresses */
 178         if (address & 1)
 179                 return 0;
 180
 181         if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 182                 return -ENOMEM;
 183
 184         /* A fake client is created on the odd address */
 185         if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
 186                 err = -ENOMEM;
 187                 goto exit_kfree1;
 188         }
 189
 190         /* Init real i2c_client */
 191         real_client = &data->client;
 192         i2c_set_clientdata(real_client, data);
 193         real_client->addr = address;
 194         real_client->adapter = adapter;
 195         real_client->driver = &max6875_driver;
 196         real_client->flags = 0;
 197         strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
 198         mutex_init(&data->update_lock);
 199
 200         /* Init fake client data */
 201         i2c_set_clientdata(fake_client, NULL);
 202         fake_client->addr = address | 1;
 203         fake_client->adapter = adapter;
 204         fake_client->driver = &max6875_driver;
 205         fake_client->flags = 0;
 206         strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
 207
 208         /* Prevent 24RF08 corruption (in case of user error) */
 209         i2c_smbus_write_quick(real_client, 0);
 210
 211         if ((err = i2c_attach_client(real_client)) != 0)
 212                 goto exit_kfree2;
 213
 214         if ((err = i2c_attach_client(fake_client)) != 0)
 215                 goto exit_detach1;
 216
 217         err = sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
 218         if (err)
 219                 goto exit_detach2;
 220
 221         return 0;
 222
 223 exit_detach2:
 224         i2c_detach_client(fake_client);
 225 exit_detach1:
 226         i2c_detach_client(real_client);
 227 exit_kfree2:
 228         kfree(fake_client);
 229 exit_kfree1:
 230         kfree(data);
 231         return err;
 232 }
 233
 234 /* Will be called for both the real client and the fake client */
 235 static int max6875_detach_client(struct i2c_client *client)
 236 {
 237         int err;
 238         struct max6875_data *data = i2c_get_clientdata(client);
 239
 240         /* data is NULL for the fake client */
 241         if (data)
 242                 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
 243
 244         err = i2c_detach_client(client);
 245         if (err)
 246                 return err;
 247
 248         if (data)               /* real client */
 249                 kfree(data);
 250         else                    /* fake client */
 251                 kfree(client);
 252         return 0;
 253 }
 254
 255 static int __init max6875_init(void)
 256 {
 257         return i2c_add_driver(&max6875_driver);
 258 }
 259
 260 static void __exit max6875_exit(void)
 261 {
 262         i2c_del_driver(&max6875_driver);
 263 }
 264
 265
 266 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 267 MODULE_DESCRIPTION("MAX6875 driver");
 268 MODULE_LICENSE("GPL");
 269
 270 module_init(max6875_init);
 271 module_exit(max6875_exit);