drivers/misc/eeprom/eeprom.c

   1 /*
   2  * Copyright (C) 1998, 1999  Frodo Looijaard <frodol@dds.nl> and
   3  *                           Philip Edelbrock <phil@netroedge.com>
   4  * Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
   5  * Copyright (C) 2003 IBM Corp.
   6  * Copyright (C) 2004 Jean Delvare <jdelvare@suse.de>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/module.h>
  21 #include <linux/device.h>
  22 #include <linux/capability.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/i2c.h>
  25 #include <linux/mutex.h>
  26
  27 /* Addresses to scan */
  28 static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
  29                                         0x55, 0x56, 0x57, I2C_CLIENT_END };
  30
  31
  32 /* Size of EEPROM in bytes */
  33 #define EEPROM_SIZE             256
  34
  35 /* possible types of eeprom devices */
  36 enum eeprom_nature {
  37         UNKNOWN,
  38         VAIO,
  39 };
  40
  41 /* Each client has this additional data */
  42 struct eeprom_data {
  43         struct mutex update_lock;
  44         u8 valid;                       /* bitfield, bit!=0 if slice is valid */
  45         unsigned long last_updated[8];  /* In jiffies, 8 slices */
  46         u8 data[EEPROM_SIZE];           /* Register values */
  47         enum eeprom_nature nature;
  48 };
  49
  50
  51 static void eeprom_update_client(struct i2c_client *client, u8 slice)
  52 {
  53         struct eeprom_data *data = i2c_get_clientdata(client);
  54         int i;
  55
  56         mutex_lock(&data->update_lock);
  57
  58         if (!(data->valid & (1 << slice)) ||
  59             time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
  60                 dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
  61
  62                 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  63                         for (i = slice << 5; i < (slice + 1) << 5; i += 32)
  64                                 if (i2c_smbus_read_i2c_block_data(client, i,
  65                                                         32, data->data + i)
  66                                                         != 32)
  67                                         goto exit;
  68                 } else {
  69                         for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
  70                                 int word = i2c_smbus_read_word_data(client, i);
  71                                 if (word < 0)
  72                                         goto exit;
  73                                 data->data[i] = word & 0xff;
  74                                 data->data[i + 1] = word >> 8;
  75                         }
  76                 }
  77                 data->last_updated[slice] = jiffies;
  78                 data->valid |= (1 << slice);
  79         }
  80 exit:
  81         mutex_unlock(&data->update_lock);
  82 }
  83
  84 static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
  85                            struct bin_attribute *bin_attr,
  86                            char *buf, loff_t off, size_t count)
  87 {
  88         struct i2c_client *client = to_i2c_client(kobj_to_dev(kobj));
  89         struct eeprom_data *data = i2c_get_clientdata(client);
  90         u8 slice;
  91
  92         /* Only refresh slices which contain requested bytes */
  93         for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
  94                 eeprom_update_client(client, slice);
  95
  96         /* Hide Vaio private settings to regular users:
  97            - BIOS passwords: bytes 0x00 to 0x0f
  98            - UUID: bytes 0x10 to 0x1f
  99            - Serial number: 0xc0 to 0xdf */
 100         if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
 101                 int i;
 102
 103                 for (i = 0; i < count; i++) {
 104                         if ((off + i <= 0x1f) ||
 105                             (off + i >= 0xc0 && off + i <= 0xdf))
 106                                 buf[i] = 0;
 107                         else
 108                                 buf[i] = data->data[off + i];
 109                 }
 110         } else {
 111                 memcpy(buf, &data->data[off], count);
 112         }
 113
 114         return count;
 115 }
 116
 117 static const struct bin_attribute eeprom_attr = {
 118         .attr = {
 119                 .name = "eeprom",
 120                 .mode = S_IRUGO,
 121         },
 122         .size = EEPROM_SIZE,
 123         .read = eeprom_read,
 124 };
 125
 126 /* Return 0 if detection is successful, -ENODEV otherwise */
 127 static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
 128 {
 129         struct i2c_adapter *adapter = client->adapter;
 130
 131         /* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
 132            addresses 0x50-0x57, but we only care about 0x50. So decline
 133            attaching to addresses >= 0x51 on DDC buses */
 134         if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
 135                 return -ENODEV;
 136
 137         /* There are four ways we can read the EEPROM data:
 138            (1) I2C block reads (faster, but unsupported by most adapters)
 139            (2) Word reads (128% overhead)
 140            (3) Consecutive byte reads (88% overhead, unsafe)
 141            (4) Regular byte data reads (265% overhead)
 142            The third and fourth methods are not implemented by this driver
 143            because all known adapters support one of the first two. */
 144         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
 145          && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
 146                 return -ENODEV;
 147
 148         strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
 149
 150         return 0;
 151 }
 152
 153 static int eeprom_probe(struct i2c_client *client,
 154                         const struct i2c_device_id *id)
 155 {
 156         struct i2c_adapter *adapter = client->adapter;
 157         struct eeprom_data *data;
 158
 159         data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
 160                             GFP_KERNEL);
 161         if (!data)
 162                 return -ENOMEM;
 163
 164         memset(data->data, 0xff, EEPROM_SIZE);
 165         i2c_set_clientdata(client, data);
 166         mutex_init(&data->update_lock);
 167         data->nature = UNKNOWN;
 168
 169         /* Detect the Vaio nature of EEPROMs.
 170            We use the "PCG-" or "VGN-" prefix as the signature. */
 171         if (client->addr == 0x57
 172          && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 173                 char name[4];
 174
 175                 name[0] = i2c_smbus_read_byte_data(client, 0x80);
 176                 name[1] = i2c_smbus_read_byte_data(client, 0x81);
 177                 name[2] = i2c_smbus_read_byte_data(client, 0x82);
 178                 name[3] = i2c_smbus_read_byte_data(client, 0x83);
 179
 180                 if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
 181                         dev_info(&client->dev, "Vaio EEPROM detected, "
 182                                  "enabling privacy protection\n");
 183                         data->nature = VAIO;
 184                 }
 185         }
 186
 187         /* create the sysfs eeprom file */
 188         return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
 189 }
 190
 191 static int eeprom_remove(struct i2c_client *client)
 192 {
 193         sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
 194
 195         return 0;
 196 }
 197
 198 static const struct i2c_device_id eeprom_id[] = {
 199         { "eeprom", 0 },
 200         { }
 201 };
 202
 203 static struct i2c_driver eeprom_driver = {
 204         .driver = {
 205                 .name   = "eeprom",
 206         },
 207         .probe          = eeprom_probe,
 208         .remove         = eeprom_remove,
 209         .id_table       = eeprom_id,
 210
 211         .class          = I2C_CLASS_DDC | I2C_CLASS_SPD,
 212         .detect         = eeprom_detect,
 213         .address_list   = normal_i2c,
 214 };
 215
 216 module_i2c_driver(eeprom_driver);
 217
 218 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
 219                 "Philip Edelbrock <phil@netroedge.com> and "
 220                 "Greg Kroah-Hartman <greg@kroah.com>");
 221 MODULE_DESCRIPTION("I2C EEPROM driver");
 222 MODULE_LICENSE("GPL");