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/init.h>
  31 #include <linux/module.h>
  32 #include <linux/slab.h>
  33 #include <linux/i2c.h>
  34 #include <linux/mutex.h>
  35
  36 /* The MAX6875 can only read/write 16 bytes at a time */
  37 #define SLICE_SIZE                      16
  38 #define SLICE_BITS                      4
  39
  40 /* USER EEPROM is at addresses 0x8100 - 0x82FF */
  41 #define USER_EEPROM_BASE                0x8100
  42 #define USER_EEPROM_SIZE                0x0200
  43 #define USER_EEPROM_SLICES              32
  44
  45 /* MAX6875 commands */
  46 #define MAX6875_CMD_BLK_READ            0x84
  47
  48 /* Each client has this additional data */
  49 struct max6875_data {
  50         struct i2c_client       *fake_client;
  51         struct mutex            update_lock;
  52
  53         u32                     valid;
  54         u8                      data[USER_EEPROM_SIZE];
  55         unsigned long           last_updated[USER_EEPROM_SLICES];
  56 };
  57
  58 static void max6875_update_slice(struct i2c_client *client, int slice)
  59 {
  60         struct max6875_data *data = i2c_get_clientdata(client);
  61         int i, j, addr;
  62         u8 *buf;
  63
  64         if (slice >= USER_EEPROM_SLICES)
  65                 return;
  66
  67         mutex_lock(&data->update_lock);
  68
  69         buf = &data->data[slice << SLICE_BITS];
  70
  71         if (!(data->valid & (1 << slice)) ||
  72             time_after(jiffies, data->last_updated[slice])) {
  73
  74                 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
  75
  76                 data->valid &= ~(1 << slice);
  77
  78                 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
  79
  80                 /* select the eeprom address */
  81                 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
  82                         dev_err(&client->dev, "address set failed\n");
  83                         goto exit_up;
  84                 }
  85
  86                 if (i2c_check_functionality(client->adapter,
  87                                             I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  88                         if (i2c_smbus_read_i2c_block_data(client,
  89                                                           MAX6875_CMD_BLK_READ,
  90                                                           SLICE_SIZE,
  91                                                           buf) != SLICE_SIZE) {
  92                                 goto exit_up;
  93                         }
  94                 } else {
  95                         for (i = 0; i < SLICE_SIZE; i++) {
  96                                 j = i2c_smbus_read_byte(client);
  97                                 if (j < 0) {
  98                                         goto exit_up;
  99                                 }
 100                                 buf[i] = j;
 101                         }
 102                 }
 103                 data->last_updated[slice] = jiffies;
 104                 data->valid |= (1 << slice);
 105         }
 106 exit_up:
 107         mutex_unlock(&data->update_lock);
 108 }
 109
 110 static ssize_t max6875_read(struct file *filp, struct kobject *kobj,
 111                             struct bin_attribute *bin_attr,
 112                             char *buf, loff_t off, size_t count)
 113 {
 114         struct i2c_client *client = kobj_to_i2c_client(kobj);
 115         struct max6875_data *data = i2c_get_clientdata(client);
 116         int slice, max_slice;
 117
 118         if (off > USER_EEPROM_SIZE)
 119                 return 0;
 120
 121         if (off + count > USER_EEPROM_SIZE)
 122                 count = USER_EEPROM_SIZE - off;
 123
 124         /* refresh slices which contain requested bytes */
 125         max_slice = (off + count - 1) >> SLICE_BITS;
 126         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 127                 max6875_update_slice(client, slice);
 128
 129         memcpy(buf, &data->data[off], count);
 130
 131         return count;
 132 }
 133
 134 static struct bin_attribute user_eeprom_attr = {
 135         .attr = {
 136                 .name = "eeprom",
 137                 .mode = S_IRUGO,
 138         },
 139         .size = USER_EEPROM_SIZE,
 140         .read = max6875_read,
 141 };
 142
 143 static int max6875_probe(struct i2c_client *client,
 144                          const struct i2c_device_id *id)
 145 {
 146         struct i2c_adapter *adapter = client->adapter;
 147         struct max6875_data *data;
 148         int err;
 149
 150         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 151                                      | I2C_FUNC_SMBUS_READ_BYTE))
 152                 return -ENODEV;
 153
 154         /* Only bind to even addresses */
 155         if (client->addr & 1)
 156                 return -ENODEV;
 157
 158         if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
 159                 return -ENOMEM;
 160
 161         /* A fake client is created on the odd address */
 162         data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1);
 163         if (!data->fake_client) {
 164                 err = -ENOMEM;
 165                 goto exit_kfree;
 166         }
 167
 168         /* Init real i2c_client */
 169         i2c_set_clientdata(client, data);
 170         mutex_init(&data->update_lock);
 171
 172         err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
 173         if (err)
 174                 goto exit_remove_fake;
 175
 176         return 0;
 177
 178 exit_remove_fake:
 179         i2c_unregister_device(data->fake_client);
 180 exit_kfree:
 181         kfree(data);
 182         return err;
 183 }
 184
 185 static int max6875_remove(struct i2c_client *client)
 186 {
 187         struct max6875_data *data = i2c_get_clientdata(client);
 188
 189         i2c_unregister_device(data->fake_client);
 190
 191         sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
 192         kfree(data);
 193
 194         return 0;
 195 }
 196
 197 static const struct i2c_device_id max6875_id[] = {
 198         { "max6875", 0 },
 199         { }
 200 };
 201
 202 static struct i2c_driver max6875_driver = {
 203         .driver = {
 204                 .name   = "max6875",
 205         },
 206         .probe          = max6875_probe,
 207         .remove         = max6875_remove,
 208         .id_table       = max6875_id,
 209 };
 210
 211 module_i2c_driver(max6875_driver);
 212
 213 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 214 MODULE_DESCRIPTION("MAX6875 driver");
 215 MODULE_LICENSE("GPL");