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 <asm/semaphore.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 semaphore        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                 .owner  = THIS_MODULE,
  72                 .name   = "max6875",
  73         },
  74         .attach_adapter = max6875_attach_adapter,
  75         .detach_client  = max6875_detach_client,
  76 };
  77
  78 static void max6875_update_slice(struct i2c_client *client, int slice)
  79 {
  80         struct max6875_data *data = i2c_get_clientdata(client);
  81         int i, j, addr;
  82         u8 *buf;
  83
  84         if (slice >= USER_EEPROM_SLICES)
  85                 return;
  86
  87         down(&data->update_lock);
  88
  89         buf = &data->data[slice << SLICE_BITS];
  90
  91         if (!(data->valid & (1 << slice)) ||
  92             time_after(jiffies, data->last_updated[slice])) {
  93
  94                 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
  95
  96                 data->valid &= ~(1 << slice);
  97
  98                 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
  99
 100                 /* select the eeprom address */
 101                 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
 102                         dev_err(&client->dev, "address set failed\n");
 103                         goto exit_up;
 104                 }
 105
 106                 if (i2c_check_functionality(client->adapter,
 107                                             I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 108                         if (i2c_smbus_read_i2c_block_data(client,
 109                                                           MAX6875_CMD_BLK_READ,
 110                                                           buf) != SLICE_SIZE) {
 111                                 goto exit_up;
 112                         }
 113                 } else {
 114                         for (i = 0; i < SLICE_SIZE; i++) {
 115                                 j = i2c_smbus_read_byte(client);
 116                                 if (j < 0) {
 117                                         goto exit_up;
 118                                 }
 119                                 buf[i] = j;
 120                         }
 121                 }
 122                 data->last_updated[slice] = jiffies;
 123                 data->valid |= (1 << slice);
 124         }
 125 exit_up:
 126         up(&data->update_lock);
 127 }
 128
 129 static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
 130                             size_t count)
 131 {
 132         struct i2c_client *client = kobj_to_i2c_client(kobj);
 133         struct max6875_data *data = i2c_get_clientdata(client);
 134         int slice, max_slice;
 135
 136         if (off > USER_EEPROM_SIZE)
 137                 return 0;
 138
 139         if (off + count > USER_EEPROM_SIZE)
 140                 count = USER_EEPROM_SIZE - off;
 141
 142         /* refresh slices which contain requested bytes */
 143         max_slice = (off + count - 1) >> SLICE_BITS;
 144         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 145                 max6875_update_slice(client, slice);
 146
 147         memcpy(buf, &data->data[off], count);
 148
 149         return count;
 150 }
 151
 152 static struct bin_attribute user_eeprom_attr = {
 153         .attr = {
 154                 .name = "eeprom",
 155                 .mode = S_IRUGO,
 156                 .owner = THIS_MODULE,
 157         },
 158         .size = USER_EEPROM_SIZE,
 159         .read = max6875_read,
 160 };
 161
 162 static int max6875_attach_adapter(struct i2c_adapter *adapter)
 163 {
 164         return i2c_probe(adapter, &addr_data, max6875_detect);
 165 }
 166
 167 /* This function is called by i2c_probe */
 168 static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
 169 {
 170         struct i2c_client *real_client;
 171         struct i2c_client *fake_client;
 172         struct max6875_data *data;
 173         int err = 0;
 174
 175         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 176                                      | I2C_FUNC_SMBUS_READ_BYTE))
 177                 return 0;
 178
 179         /* Only check even addresses */
 180         if (address & 1)
 181                 return 0;
 182
 183         if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 184                 return -ENOMEM;
 185
 186         /* A fake client is created on the odd address */
 187         if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
 188                 err = -ENOMEM;
 189                 goto exit_kfree1;
 190         }
 191
 192         /* Init real i2c_client */
 193         real_client = &data->client;
 194         i2c_set_clientdata(real_client, data);
 195         real_client->addr = address;
 196         real_client->adapter = adapter;
 197         real_client->driver = &max6875_driver;
 198         real_client->flags = 0;
 199         strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
 200         init_MUTEX(&data->update_lock);
 201
 202         /* Init fake client data */
 203         /* set the client data to the i2c_client so that it will get freed */
 204         i2c_set_clientdata(fake_client, fake_client);
 205         fake_client->addr = address | 1;
 206         fake_client->adapter = adapter;
 207         fake_client->driver = &max6875_driver;
 208         fake_client->flags = 0;
 209         strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
 210
 211         /* Prevent 24RF08 corruption (in case of user error) */
 212         i2c_smbus_write_quick(real_client, 0);
 213
 214         if ((err = i2c_attach_client(real_client)) != 0)
 215                 goto exit_kfree2;
 216
 217         if ((err = i2c_attach_client(fake_client)) != 0)
 218                 goto exit_detach;
 219
 220         sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
 221
 222         return 0;
 223
 224 exit_detach:
 225         i2c_detach_client(real_client);
 226 exit_kfree2:
 227         kfree(fake_client);
 228 exit_kfree1:
 229         kfree(data);
 230         return err;
 231 }
 232
 233 static int max6875_detach_client(struct i2c_client *client)
 234 {
 235         int err;
 236
 237         err = i2c_detach_client(client);
 238         if (err)
 239                 return err;
 240         kfree(i2c_get_clientdata(client));
 241         return 0;
 242 }
 243
 244 static int __init max6875_init(void)
 245 {
 246         return i2c_add_driver(&max6875_driver);
 247 }
 248
 249 static void __exit max6875_exit(void)
 250 {
 251         i2c_del_driver(&max6875_driver);
 252 }
 253
 254
 255 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 256 MODULE_DESCRIPTION("MAX6875 driver");
 257 MODULE_LICENSE("GPL");
 258
 259 module_init(max6875_init);
 260 module_exit(max6875_exit);