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/jiffies.h>
  23 #include <linux/i2c.h>
  24 #include <linux/mutex.h>
  25
  26 /* Addresses to scan */
  27 static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
  28                                         0x55, 0x56, 0x57, I2C_CLIENT_END };
  29
  30
  31 /* Size of EEPROM in bytes */
  32 #define EEPROM_SIZE             256
  33
  34 /* possible types of eeprom devices */
  35 enum eeprom_nature {
  36         UNKNOWN,
  37         VAIO,
  38 };
  39
  40 /* Each client has this additional data */
  41 struct eeprom_data {
  42         struct mutex update_lock;
  43         u8 valid;                       /* bitfield, bit!=0 if slice is valid */
  44         unsigned long last_updated[8];  /* In jiffies, 8 slices */
  45         u8 data[EEPROM_SIZE];           /* Register values */
  46         enum eeprom_nature nature;
  47 };
  48
  49
  50 static void eeprom_update_client(struct i2c_client *client, u8 slice)
  51 {
  52         struct eeprom_data *data = i2c_get_clientdata(client);
  53         int i;
  54
  55         mutex_lock(&data->update_lock);
  56
  57         if (!(data->valid & (1 << slice)) ||
  58             time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
  59                 dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
  60
  61                 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  62                         for (i = slice << 5; i < (slice + 1) << 5; i += 32)
  63                                 if (i2c_smbus_read_i2c_block_data(client, i,
  64                                                         32, data->data + i)
  65                                                         != 32)
  66                                         goto exit;
  67                 } else {
  68                         for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
  69                                 int word = i2c_smbus_read_word_data(client, i);
  70                                 if (word < 0)
  71                                         goto exit;
  72                                 data->data[i] = word & 0xff;
  73                                 data->data[i + 1] = word >> 8;
  74                         }
  75                 }
  76                 data->last_updated[slice] = jiffies;
  77                 data->valid |= (1 << slice);
  78         }
  79 exit:
  80         mutex_unlock(&data->update_lock);
  81 }
  82
  83 static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
  84                            struct bin_attribute *bin_attr,
  85                            char *buf, loff_t off, size_t count)
  86 {
  87         struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
  88         struct eeprom_data *data = i2c_get_clientdata(client);
  89         u8 slice;
  90
  91         if (off > EEPROM_SIZE)
  92                 return 0;
  93         if (off + count > EEPROM_SIZE)
  94                 count = EEPROM_SIZE - off;
  95
  96         /* Only refresh slices which contain requested bytes */
  97         for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
  98                 eeprom_update_client(client, slice);
  99
 100         /* Hide Vaio private settings to regular users:
 101            - BIOS passwords: bytes 0x00 to 0x0f
 102            - UUID: bytes 0x10 to 0x1f
 103            - Serial number: 0xc0 to 0xdf */
 104         if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
 105                 int i;
 106
 107                 for (i = 0; i < count; i++) {
 108                         if ((off + i <= 0x1f) ||
 109                             (off + i >= 0xc0 && off + i <= 0xdf))
 110                                 buf[i] = 0;
 111                         else
 112                                 buf[i] = data->data[off + i];
 113                 }
 114         } else {
 115                 memcpy(buf, &data->data[off], count);
 116         }
 117
 118         return count;
 119 }
 120
 121 static struct bin_attribute eeprom_attr = {
 122         .attr = {
 123                 .name = "eeprom",
 124                 .mode = S_IRUGO,
 125         },
 126         .size = EEPROM_SIZE,
 127         .read = eeprom_read,
 128 };
 129
 130 /* Return 0 if detection is successful, -ENODEV otherwise */
 131 static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
 132 {
 133         struct i2c_adapter *adapter = client->adapter;
 134
 135         /* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
 136            addresses 0x50-0x57, but we only care about 0x50. So decline
 137            attaching to addresses >= 0x51 on DDC buses */
 138         if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
 139                 return -ENODEV;
 140
 141         /* There are four ways we can read the EEPROM data:
 142            (1) I2C block reads (faster, but unsupported by most adapters)
 143            (2) Word reads (128% overhead)
 144            (3) Consecutive byte reads (88% overhead, unsafe)
 145            (4) Regular byte data reads (265% overhead)
 146            The third and fourth methods are not implemented by this driver
 147            because all known adapters support one of the first two. */
 148         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
 149          && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
 150                 return -ENODEV;
 151
 152         strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
 153
 154         return 0;
 155 }
 156
 157 static int eeprom_probe(struct i2c_client *client,
 158                         const struct i2c_device_id *id)
 159 {
 160         struct i2c_adapter *adapter = client->adapter;
 161         struct eeprom_data *data;
 162
 163         data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
 164                             GFP_KERNEL);
 165         if (!data)
 166                 return -ENOMEM;
 167
 168         memset(data->data, 0xff, EEPROM_SIZE);
 169         i2c_set_clientdata(client, data);
 170         mutex_init(&data->update_lock);
 171         data->nature = UNKNOWN;
 172
 173         /* Detect the Vaio nature of EEPROMs.
 174            We use the "PCG-" or "VGN-" prefix as the signature. */
 175         if (client->addr == 0x57
 176          && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 177                 char name[4];
 178
 179                 name[0] = i2c_smbus_read_byte_data(client, 0x80);
 180                 name[1] = i2c_smbus_read_byte_data(client, 0x81);
 181                 name[2] = i2c_smbus_read_byte_data(client, 0x82);
 182                 name[3] = i2c_smbus_read_byte_data(client, 0x83);
 183
 184                 if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
 185                         dev_info(&client->dev, "Vaio EEPROM detected, "
 186                                  "enabling privacy protection\n");
 187                         data->nature = VAIO;
 188                 }
 189         }
 190
 191         /* create the sysfs eeprom file */
 192         return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
 193 }
 194
 195 static int eeprom_remove(struct i2c_client *client)
 196 {
 197         sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
 198
 199         return 0;
 200 }
 201
 202 static const struct i2c_device_id eeprom_id[] = {
 203         { "eeprom", 0 },
 204         { }
 205 };
 206
 207 static struct i2c_driver eeprom_driver = {
 208         .driver = {
 209                 .name   = "eeprom",
 210         },
 211         .probe          = eeprom_probe,
 212         .remove         = eeprom_remove,
 213         .id_table       = eeprom_id,
 214
 215         .class          = I2C_CLASS_DDC | I2C_CLASS_SPD,
 216         .detect         = eeprom_detect,
 217         .address_list   = normal_i2c,
 218 };
 219
 220 module_i2c_driver(eeprom_driver);
 221
 222 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
 223                 "Philip Edelbrock <phil@netroedge.com> and "
 224                 "Greg Kroah-Hartman <greg@kroah.com>");
 225 MODULE_DESCRIPTION("I2C EEPROM driver");
 226 MODULE_LICENSE("GPL");