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 <khali@linux-fr.org>
   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     You should have received a copy of the GNU General Public License
  19     along with this program; if not, write to the Free Software
  20     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/slab.h>
  27 #include <linux/jiffies.h>
  28 #include <linux/i2c.h>
  29 #include <linux/mutex.h>
  30
  31 /* Addresses to scan */
  32 static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
  33                                         0x55, 0x56, 0x57, I2C_CLIENT_END };
  34
  35 /* Insmod parameters */
  36 I2C_CLIENT_INSMOD_1(eeprom);
  37
  38
  39 /* Size of EEPROM in bytes */
  40 #define EEPROM_SIZE             256
  41
  42 /* possible types of eeprom devices */
  43 enum eeprom_nature {
  44         UNKNOWN,
  45         VAIO,
  46 };
  47
  48 /* Each client has this additional data */
  49 struct eeprom_data {
  50         struct mutex update_lock;
  51         u8 valid;                       /* bitfield, bit!=0 if slice is valid */
  52         unsigned long last_updated[8];  /* In jiffies, 8 slices */
  53         u8 data[EEPROM_SIZE];           /* Register values */
  54         enum eeprom_nature nature;
  55 };
  56
  57
  58 static void eeprom_update_client(struct i2c_client *client, u8 slice)
  59 {
  60         struct eeprom_data *data = i2c_get_clientdata(client);
  61         int i;
  62
  63         mutex_lock(&data->update_lock);
  64
  65         if (!(data->valid & (1 << slice)) ||
  66             time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
  67                 dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
  68
  69                 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  70                         for (i = slice << 5; i < (slice + 1) << 5; i += 32)
  71                                 if (i2c_smbus_read_i2c_block_data(client, i,
  72                                                         32, data->data + i)
  73                                                         != 32)
  74                                         goto exit;
  75                 } else {
  76                         for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
  77                                 int word = i2c_smbus_read_word_data(client, i);
  78                                 if (word < 0)
  79                                         goto exit;
  80                                 data->data[i] = word & 0xff;
  81                                 data->data[i + 1] = word >> 8;
  82                         }
  83                 }
  84                 data->last_updated[slice] = jiffies;
  85                 data->valid |= (1 << slice);
  86         }
  87 exit:
  88         mutex_unlock(&data->update_lock);
  89 }
  90
  91 static ssize_t eeprom_read(struct kobject *kobj, struct bin_attribute *bin_attr,
  92                            char *buf, loff_t off, size_t count)
  93 {
  94         struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
  95         struct eeprom_data *data = i2c_get_clientdata(client);
  96         u8 slice;
  97
  98         if (off > EEPROM_SIZE)
  99                 return 0;
 100         if (off + count > EEPROM_SIZE)
 101                 count = EEPROM_SIZE - off;
 102
 103         /* Only refresh slices which contain requested bytes */
 104         for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
 105                 eeprom_update_client(client, slice);
 106
 107         /* Hide Vaio private settings to regular users:
 108            - BIOS passwords: bytes 0x00 to 0x0f
 109            - UUID: bytes 0x10 to 0x1f
 110            - Serial number: 0xc0 to 0xdf */
 111         if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
 112                 int i;
 113
 114                 for (i = 0; i < count; i++) {
 115                         if ((off + i <= 0x1f) ||
 116                             (off + i >= 0xc0 && off + i <= 0xdf))
 117                                 buf[i] = 0;
 118                         else
 119                                 buf[i] = data->data[off + i];
 120                 }
 121         } else {
 122                 memcpy(buf, &data->data[off], count);
 123         }
 124
 125         return count;
 126 }
 127
 128 static struct bin_attribute eeprom_attr = {
 129         .attr = {
 130                 .name = "eeprom",
 131                 .mode = S_IRUGO,
 132         },
 133         .size = EEPROM_SIZE,
 134         .read = eeprom_read,
 135 };
 136
 137 /* Return 0 if detection is successful, -ENODEV otherwise */
 138 static int eeprom_detect(struct i2c_client *client, int kind,
 139                          struct i2c_board_info *info)
 140 {
 141         struct i2c_adapter *adapter = client->adapter;
 142
 143         /* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
 144            addresses 0x50-0x57, but we only care about 0x50. So decline
 145            attaching to addresses >= 0x51 on DDC buses */
 146         if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
 147                 return -ENODEV;
 148
 149         /* There are four ways we can read the EEPROM data:
 150            (1) I2C block reads (faster, but unsupported by most adapters)
 151            (2) Word reads (128% overhead)
 152            (3) Consecutive byte reads (88% overhead, unsafe)
 153            (4) Regular byte data reads (265% overhead)
 154            The third and fourth methods are not implemented by this driver
 155            because all known adapters support one of the first two. */
 156         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
 157          && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
 158                 return -ENODEV;
 159
 160         strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
 161
 162         return 0;
 163 }
 164
 165 static int eeprom_probe(struct i2c_client *client,
 166                         const struct i2c_device_id *id)
 167 {
 168         struct i2c_adapter *adapter = client->adapter;
 169         struct eeprom_data *data;
 170         int err;
 171
 172         if (!(data = kzalloc(sizeof(struct eeprom_data), GFP_KERNEL))) {
 173                 err = -ENOMEM;
 174                 goto exit;
 175         }
 176
 177         memset(data->data, 0xff, EEPROM_SIZE);
 178         i2c_set_clientdata(client, data);
 179         mutex_init(&data->update_lock);
 180         data->nature = UNKNOWN;
 181
 182         /* Detect the Vaio nature of EEPROMs.
 183            We use the "PCG-" or "VGN-" prefix as the signature. */
 184         if (client->addr == 0x57
 185          && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 186                 char name[4];
 187
 188                 name[0] = i2c_smbus_read_byte_data(client, 0x80);
 189                 name[1] = i2c_smbus_read_byte_data(client, 0x81);
 190                 name[2] = i2c_smbus_read_byte_data(client, 0x82);
 191                 name[3] = i2c_smbus_read_byte_data(client, 0x83);
 192
 193                 if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
 194                         dev_info(&client->dev, "Vaio EEPROM detected, "
 195                                  "enabling privacy protection\n");
 196                         data->nature = VAIO;
 197                 }
 198         }
 199
 200         /* create the sysfs eeprom file */
 201         err = sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
 202         if (err)
 203                 goto exit_kfree;
 204
 205         return 0;
 206
 207 exit_kfree:
 208         kfree(data);
 209 exit:
 210         return err;
 211 }
 212
 213 static int eeprom_remove(struct i2c_client *client)
 214 {
 215         sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
 216         kfree(i2c_get_clientdata(client));
 217
 218         return 0;
 219 }
 220
 221 static const struct i2c_device_id eeprom_id[] = {
 222         { "eeprom", 0 },
 223         { }
 224 };
 225
 226 static struct i2c_driver eeprom_driver = {
 227         .driver = {
 228                 .name   = "eeprom",
 229         },
 230         .probe          = eeprom_probe,
 231         .remove         = eeprom_remove,
 232         .id_table       = eeprom_id,
 233
 234         .class          = I2C_CLASS_DDC | I2C_CLASS_SPD,
 235         .detect         = eeprom_detect,
 236         .address_data   = &addr_data,
 237 };
 238
 239 static int __init eeprom_init(void)
 240 {
 241         return i2c_add_driver(&eeprom_driver);
 242 }
 243
 244 static void __exit eeprom_exit(void)
 245 {
 246         i2c_del_driver(&eeprom_driver);
 247 }
 248
 249
 250 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
 251                 "Philip Edelbrock <phil@netroedge.com> and "
 252                 "Greg Kroah-Hartman <greg@kroah.com>");
 253 MODULE_DESCRIPTION("I2C EEPROM driver");
 254 MODULE_LICENSE("GPL");
 255
 256 module_init(eeprom_init);
 257 module_exit(eeprom_exit);