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