drivers/misc/eeprom/max6875.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * max6875.c - driver for MAX6874/MAX6875
   4  *
   5  * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
   6  *
   7  * Based on eeprom.c
   8  *
   9  * The MAX6875 has a bank of registers and two banks of EEPROM.
  10  * Address ranges are defined as follows:
  11  *  * 0x0000 - 0x0046 = configuration registers
  12  *  * 0x8000 - 0x8046 = configuration EEPROM
  13  *  * 0x8100 - 0x82FF = user EEPROM
  14  *
  15  * This driver makes the user EEPROM available for read.
  16  *
  17  * The registers & config EEPROM should be accessed via i2c-dev.
  18  *
  19  * The MAX6875 ignores the lowest address bit, so each chip responds to
  20  * two addresses - 0x50/0x51 and 0x52/0x53.
  21  *
  22  * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
  23  * address, so this driver is destructive if loaded for the wrong EEPROM chip.
  24  */
  25
  26 #include <linux/kernel.h>
  27 #include <linux/module.h>
  28 #include <linux/slab.h>
  29 #include <linux/i2c.h>
  30 #include <linux/mutex.h>
  31
  32 /* The MAX6875 can only read/write 16 bytes at a time */
  33 #define SLICE_SIZE                      16
  34 #define SLICE_BITS                      4
  35
  36 /* USER EEPROM is at addresses 0x8100 - 0x82FF */
  37 #define USER_EEPROM_BASE                0x8100
  38 #define USER_EEPROM_SIZE                0x0200
  39 #define USER_EEPROM_SLICES              32
  40
  41 /* MAX6875 commands */
  42 #define MAX6875_CMD_BLK_READ            0x84
  43
  44 /* Each client has this additional data */
  45 struct max6875_data {
  46         struct i2c_client       *fake_client;
  47         struct mutex            update_lock;
  48
  49         u32                     valid;
  50         u8                      data[USER_EEPROM_SIZE];
  51         unsigned long           last_updated[USER_EEPROM_SLICES];
  52 };
  53
  54 static void max6875_update_slice(struct i2c_client *client, int slice)
  55 {
  56         struct max6875_data *data = i2c_get_clientdata(client);
  57         int i, j, addr;
  58         u8 *buf;
  59
  60         if (slice >= USER_EEPROM_SLICES)
  61                 return;
  62
  63         mutex_lock(&data->update_lock);
  64
  65         buf = &data->data[slice << SLICE_BITS];
  66
  67         if (!(data->valid & (1 << slice)) ||
  68             time_after(jiffies, data->last_updated[slice])) {
  69
  70                 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
  71
  72                 data->valid &= ~(1 << slice);
  73
  74                 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
  75
  76                 /* select the eeprom address */
  77                 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
  78                         dev_err(&client->dev, "address set failed\n");
  79                         goto exit_up;
  80                 }
  81
  82                 if (i2c_check_functionality(client->adapter,
  83                                             I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  84                         if (i2c_smbus_read_i2c_block_data(client,
  85                                                           MAX6875_CMD_BLK_READ,
  86                                                           SLICE_SIZE,
  87                                                           buf) != SLICE_SIZE) {
  88                                 goto exit_up;
  89                         }
  90                 } else {
  91                         for (i = 0; i < SLICE_SIZE; i++) {
  92                                 j = i2c_smbus_read_byte(client);
  93                                 if (j < 0) {
  94                                         goto exit_up;
  95                                 }
  96                                 buf[i] = j;
  97                         }
  98                 }
  99                 data->last_updated[slice] = jiffies;
 100                 data->valid |= (1 << slice);
 101         }
 102 exit_up:
 103         mutex_unlock(&data->update_lock);
 104 }
 105
 106 static ssize_t max6875_read(struct file *filp, struct kobject *kobj,
 107                             struct bin_attribute *bin_attr,
 108                             char *buf, loff_t off, size_t count)
 109 {
 110         struct i2c_client *client = kobj_to_i2c_client(kobj);
 111         struct max6875_data *data = i2c_get_clientdata(client);
 112         int slice, max_slice;
 113
 114         /* refresh slices which contain requested bytes */
 115         max_slice = (off + count - 1) >> SLICE_BITS;
 116         for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
 117                 max6875_update_slice(client, slice);
 118
 119         memcpy(buf, &data->data[off], count);
 120
 121         return count;
 122 }
 123
 124 static const struct bin_attribute user_eeprom_attr = {
 125         .attr = {
 126                 .name = "eeprom",
 127                 .mode = S_IRUGO,
 128         },
 129         .size = USER_EEPROM_SIZE,
 130         .read = max6875_read,
 131 };
 132
 133 static int max6875_probe(struct i2c_client *client,
 134                          const struct i2c_device_id *id)
 135 {
 136         struct i2c_adapter *adapter = client->adapter;
 137         struct max6875_data *data;
 138         int err;
 139
 140         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
 141                                      | I2C_FUNC_SMBUS_READ_BYTE))
 142                 return -ENODEV;
 143
 144         /* Only bind to even addresses */
 145         if (client->addr & 1)
 146                 return -ENODEV;
 147
 148         data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL);
 149         if (!data)
 150                 return -ENOMEM;
 151
 152         /* A fake client is created on the odd address */
 153         data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1);
 154         if (IS_ERR(data->fake_client)) {
 155                 err = PTR_ERR(data->fake_client);
 156                 goto exit_kfree;
 157         }
 158
 159         /* Init real i2c_client */
 160         i2c_set_clientdata(client, data);
 161         mutex_init(&data->update_lock);
 162
 163         err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
 164         if (err)
 165                 goto exit_remove_fake;
 166
 167         return 0;
 168
 169 exit_remove_fake:
 170         i2c_unregister_device(data->fake_client);
 171 exit_kfree:
 172         kfree(data);
 173         return err;
 174 }
 175
 176 static int max6875_remove(struct i2c_client *client)
 177 {
 178         struct max6875_data *data = i2c_get_clientdata(client);
 179
 180         i2c_unregister_device(data->fake_client);
 181
 182         sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
 183         kfree(data);
 184
 185         return 0;
 186 }
 187
 188 static const struct i2c_device_id max6875_id[] = {
 189         { "max6875", 0 },
 190         { }
 191 };
 192 MODULE_DEVICE_TABLE(i2c, max6875_id);
 193
 194 static struct i2c_driver max6875_driver = {
 195         .driver = {
 196                 .name   = "max6875",
 197         },
 198         .probe          = max6875_probe,
 199         .remove         = max6875_remove,
 200         .id_table       = max6875_id,
 201 };
 202
 203 module_i2c_driver(max6875_driver);
 204
 205 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 206 MODULE_DESCRIPTION("MAX6875 driver");
 207 MODULE_LICENSE("GPL");