drivers/misc/eeprom/max6875.c

   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         if (off > USER_EEPROM_SIZE)
 118                 return 0;
 119
 120         if (off + count > USER_EEPROM_SIZE)
 121                 count = USER_EEPROM_SIZE - off;
 122
 123         /* refresh slices which contain requested bytes */
 124         max_slice = (off + count - 1) >> SLICE_BITS;
 125         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 126                 max6875_update_slice(client, slice);
 127
 128         memcpy(buf, &data->data[off], count);
 129
 130         return count;
 131 }
 132
 133 static struct bin_attribute user_eeprom_attr = {
 134         .attr = {
 135                 .name = "eeprom",
 136                 .mode = S_IRUGO,
 137         },
 138         .size = USER_EEPROM_SIZE,
 139         .read = max6875_read,
 140 };
 141
 142 static int max6875_probe(struct i2c_client *client,
 143                          const struct i2c_device_id *id)
 144 {
 145         struct i2c_adapter *adapter = client->adapter;
 146         struct max6875_data *data;
 147         int err;
 148
 149         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 150                                      | I2C_FUNC_SMBUS_READ_BYTE))
 151                 return -ENODEV;
 152
 153         /* Only bind to even addresses */
 154         if (client->addr & 1)
 155                 return -ENODEV;
 156
 157         if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 158                 return -ENOMEM;
 159
 160         /* A fake client is created on the odd address */
 161         data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1);
 162         if (!data->fake_client) {
 163                 err = -ENOMEM;
 164                 goto exit_kfree;
 165         }
 166
 167         /* Init real i2c_client */
 168         i2c_set_clientdata(client, data);
 169         mutex_init(&data->update_lock);
 170
 171         err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
 172         if (err)
 173                 goto exit_remove_fake;
 174
 175         return 0;
 176
 177 exit_remove_fake:
 178         i2c_unregister_device(data->fake_client);
 179 exit_kfree:
 180         kfree(data);
 181         return err;
 182 }
 183
 184 static int max6875_remove(struct i2c_client *client)
 185 {
 186         struct max6875_data *data = i2c_get_clientdata(client);
 187
 188         i2c_unregister_device(data->fake_client);
 189
 190         sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
 191         kfree(data);
 192
 193         return 0;
 194 }
 195
 196 static const struct i2c_device_id max6875_id[] = {
 197         { "max6875", 0 },
 198         { }
 199 };
 200
 201 static struct i2c_driver max6875_driver = {
 202         .driver = {
 203                 .name   = "max6875",
 204         },
 205         .probe          = max6875_probe,
 206         .remove         = max6875_remove,
 207         .id_table       = max6875_id,
 208 };
 209
 210 module_i2c_driver(max6875_driver);
 211
 212 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 213 MODULE_DESCRIPTION("MAX6875 driver");
 214 MODULE_LICENSE("GPL");