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/i2c-sensor.h>
  35 #include <asm/semaphore.h>
  36
  37 /* Do not scan - the MAX6875 access method will write to some EEPROM chips */
  38 static unsigned short normal_i2c[] = {I2C_CLIENT_END};
  39 static unsigned int normal_isa[] = {I2C_CLIENT_ISA_END};
  40
  41 /* Insmod parameters */
  42 SENSORS_INSMOD_1(max6875);
  43
  44 /* The MAX6875 can only read/write 16 bytes at a time */
  45 #define SLICE_SIZE                      16
  46 #define SLICE_BITS                      4
  47
  48 /* USER EEPROM is at addresses 0x8100 - 0x82FF */
  49 #define USER_EEPROM_BASE                0x8100
  50 #define USER_EEPROM_SIZE                0x0200
  51 #define USER_EEPROM_SLICES              32
  52
  53 /* MAX6875 commands */
  54 #define MAX6875_CMD_BLK_READ            0x84
  55
  56 /* Each client has this additional data */
  57 struct max6875_data {
  58         struct i2c_client       client;
  59         struct semaphore        update_lock;
  60
  61         u32                     valid;
  62         u8                      data[USER_EEPROM_SIZE];
  63         unsigned long           last_updated[USER_EEPROM_SLICES];
  64 };
  65
  66 static int max6875_attach_adapter(struct i2c_adapter *adapter);
  67 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
  68 static int max6875_detach_client(struct i2c_client *client);
  69
  70 /* This is the driver that will be inserted */
  71 static struct i2c_driver max6875_driver = {
  72         .owner          = THIS_MODULE,
  73         .name           = "max6875",
  74         .flags          = I2C_DF_NOTIFY,
  75         .attach_adapter = max6875_attach_adapter,
  76         .detach_client  = max6875_detach_client,
  77 };
  78
  79 static void max6875_update_slice(struct i2c_client *client, int slice)
  80 {
  81         struct max6875_data *data = i2c_get_clientdata(client);
  82         int i, j, addr;
  83         u8 *buf;
  84         int retval = 0;
  85
  86         if (slice >= USER_EEPROM_SLICES)
  87                 return;
  88
  89         down(&data->update_lock);
  90
  91         buf = &data->data[slice << SLICE_BITS];
  92
  93         if (!(data->valid & (1 << slice)) ||
  94             time_after(jiffies, data->last_updated[slice])) {
  95
  96                 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
  97
  98                 data->valid &= ~(1 << slice);
  99
 100                 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
 101
 102                 /* select the eeprom address */
 103                 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
 104                         dev_err(&client->dev, "address set failed\n");
 105                         retval = -1;
 106                         goto exit_up;
 107                 }
 108
 109                 if (i2c_check_functionality(client->adapter,
 110                                             I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 111                         if (i2c_smbus_read_i2c_block_data(client,
 112                                                           MAX6875_CMD_BLK_READ,
 113                                                           buf) != SLICE_SIZE) {
 114                                 retval = -1;
 115                                 goto exit_up;
 116                         }
 117                 } else {
 118                         for (i = 0; i < SLICE_SIZE; i++) {
 119                                 j = i2c_smbus_read_byte(client);
 120                                 if (j < 0) {
 121                                         retval = -1;
 122                                         goto exit_up;
 123                                 }
 124                                 buf[i] = j;
 125                         }
 126                 }
 127                 data->last_updated[slice] = jiffies;
 128                 data->valid |= (1 << slice);
 129         }
 130 exit_up:
 131         up(&data->update_lock);
 132 }
 133
 134 static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
 135                             size_t count)
 136 {
 137         struct i2c_client *client = kobj_to_i2c_client(kobj);
 138         struct max6875_data *data = i2c_get_clientdata(client);
 139         int slice, max_slice;
 140
 141         if (off > USER_EEPROM_SIZE)
 142                 return 0;
 143
 144         if (off + count > USER_EEPROM_SIZE)
 145                 count = USER_EEPROM_SIZE - off;
 146
 147         /* refresh slices which contain requested bytes */
 148         max_slice = (off + count - 1) >> SLICE_BITS;
 149         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 150                 max6875_update_slice(client, slice);
 151
 152         memcpy(buf, &data->data[off], count);
 153
 154         return count;
 155 }
 156
 157 static struct bin_attribute user_eeprom_attr = {
 158         .attr = {
 159                 .name = "eeprom",
 160                 .mode = S_IRUGO,
 161                 .owner = THIS_MODULE,
 162         },
 163         .size = USER_EEPROM_SIZE,
 164         .read = max6875_read,
 165 };
 166
 167 static int max6875_attach_adapter(struct i2c_adapter *adapter)
 168 {
 169         return i2c_detect(adapter, &addr_data, max6875_detect);
 170 }
 171
 172 /* This function is called by i2c_detect */
 173 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
 174 {
 175         struct i2c_client *real_client;
 176         struct i2c_client *fake_client;
 177         struct max6875_data *data;
 178         int err = 0;
 179
 180         /* Prevent 24rf08 corruption (in case of user error) */
 181         if (kind < 0)
 182                 i2c_smbus_xfer(adapter, address, 0, 0, 0,
 183                                I2C_SMBUS_QUICK, NULL);
 184
 185         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
 186                                      | I2C_FUNC_SMBUS_READ_BYTE))
 187                 return 0;
 188
 189         /* Only check even addresses */
 190         if (address & 1)
 191                 return 0;
 192
 193         if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 194                 return -ENOMEM;
 195         memset(data, 0, sizeof(struct max6875_data));
 196
 197         /* A fake client is created on the odd address */
 198         if (!(fake_client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
 199                 err = -ENOMEM;
 200                 goto exit_kfree1;
 201         }
 202         memset(fake_client, 0, sizeof(struct i2c_client));
 203
 204         /* Init real i2c_client */
 205         real_client = &data->client;
 206         i2c_set_clientdata(real_client, data);
 207         real_client->addr = address;
 208         real_client->adapter = adapter;
 209         real_client->driver = &max6875_driver;
 210         real_client->flags = 0;
 211         strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
 212         init_MUTEX(&data->update_lock);
 213
 214         /* Init fake client data */
 215         /* set the client data to the i2c_client so that it will get freed */
 216         i2c_set_clientdata(fake_client, fake_client);
 217         fake_client->addr = address | 1;
 218         fake_client->adapter = adapter;
 219         fake_client->driver = &max6875_driver;
 220         fake_client->flags = 0;
 221         strlcpy(fake_client->name, "max6875-dummy", I2C_NAME_SIZE);
 222
 223         /* Prevent 24RF08 corruption (in case of user error) */
 224         i2c_smbus_write_quick(real_client, 0);
 225
 226         if ((err = i2c_attach_client(real_client)) != 0)
 227                 goto exit_kfree2;
 228
 229         if ((err = i2c_attach_client(fake_client)) != 0)
 230                 goto exit_detach;
 231
 232         sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
 233
 234         return 0;
 235
 236 exit_detach:
 237         i2c_detach_client(real_client);
 238 exit_kfree2:
 239         kfree(fake_client);
 240 exit_kfree1:
 241         kfree(data);
 242         return err;
 243 }
 244
 245 static int max6875_detach_client(struct i2c_client *client)
 246 {
 247         int err;
 248
 249         err = i2c_detach_client(client);
 250         if (err) {
 251                 dev_err(&client->dev, "i2c_detach_client() failed\n");
 252                 return err;
 253         }
 254         kfree(i2c_get_clientdata(client));
 255         return 0;
 256 }
 257
 258 static int __init max6875_init(void)
 259 {
 260         return i2c_add_driver(&max6875_driver);
 261 }
 262
 263 static void __exit max6875_exit(void)
 264 {
 265         i2c_del_driver(&max6875_driver);
 266 }
 267
 268
 269 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 270 MODULE_DESCRIPTION("MAX6875 driver");
 271 MODULE_LICENSE("GPL");
 272
 273 module_init(max6875_init);
 274 module_exit(max6875_exit);