drivers/misc/eeprom/eeprom.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 1998, 1999  Frodo Looijaard <frodol@dds.nl> and
   4  *                           Philip Edelbrock <phil@netroedge.com>
   5  * Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
   6  * Copyright (C) 2003 IBM Corp.
   7  * Copyright (C) 2004 Jean Delvare <jdelvare@suse.de>
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/device.h>
  13 #include <linux/capability.h>
  14 #include <linux/jiffies.h>
  15 #include <linux/i2c.h>
  16 #include <linux/mutex.h>
  17
  18 /* Addresses to scan */
  19 static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
  20                                         0x55, 0x56, 0x57, I2C_CLIENT_END };
  21
  22
  23 /* Size of EEPROM in bytes */
  24 #define EEPROM_SIZE             256
  25
  26 /* possible types of eeprom devices */
  27 enum eeprom_nature {
  28         UNKNOWN,
  29         VAIO,
  30 };
  31
  32 /* Each client has this additional data */
  33 struct eeprom_data {
  34         struct mutex update_lock;
  35         u8 valid;                       /* bitfield, bit!=0 if slice is valid */
  36         unsigned long last_updated[8];  /* In jiffies, 8 slices */
  37         u8 data[EEPROM_SIZE];           /* Register values */
  38         enum eeprom_nature nature;
  39 };
  40
  41
  42 static void eeprom_update_client(struct i2c_client *client, u8 slice)
  43 {
  44         struct eeprom_data *data = i2c_get_clientdata(client);
  45         int i;
  46
  47         mutex_lock(&data->update_lock);
  48
  49         if (!(data->valid & (1 << slice)) ||
  50             time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
  51                 dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
  52
  53                 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
  54                         for (i = slice << 5; i < (slice + 1) << 5; i += 32)
  55                                 if (i2c_smbus_read_i2c_block_data(client, i,
  56                                                         32, data->data + i)
  57                                                         != 32)
  58                                         goto exit;
  59                 } else {
  60                         for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
  61                                 int word = i2c_smbus_read_word_data(client, i);
  62                                 if (word < 0)
  63                                         goto exit;
  64                                 data->data[i] = word & 0xff;
  65                                 data->data[i + 1] = word >> 8;
  66                         }
  67                 }
  68                 data->last_updated[slice] = jiffies;
  69                 data->valid |= (1 << slice);
  70         }
  71 exit:
  72         mutex_unlock(&data->update_lock);
  73 }
  74
  75 static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
  76                            struct bin_attribute *bin_attr,
  77                            char *buf, loff_t off, size_t count)
  78 {
  79         struct i2c_client *client = kobj_to_i2c_client(kobj);
  80         struct eeprom_data *data = i2c_get_clientdata(client);
  81         u8 slice;
  82
  83         /* Only refresh slices which contain requested bytes */
  84         for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
  85                 eeprom_update_client(client, slice);
  86
  87         /* Hide Vaio private settings to regular users:
  88            - BIOS passwords: bytes 0x00 to 0x0f
  89            - UUID: bytes 0x10 to 0x1f
  90            - Serial number: 0xc0 to 0xdf */
  91         if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
  92                 int i;
  93
  94                 for (i = 0; i < count; i++) {
  95                         if ((off + i <= 0x1f) ||
  96                             (off + i >= 0xc0 && off + i <= 0xdf))
  97                                 buf[i] = 0;
  98                         else
  99                                 buf[i] = data->data[off + i];
 100                 }
 101         } else {
 102                 memcpy(buf, &data->data[off], count);
 103         }
 104
 105         return count;
 106 }
 107
 108 static const struct bin_attribute eeprom_attr = {
 109         .attr = {
 110                 .name = "eeprom",
 111                 .mode = S_IRUGO,
 112         },
 113         .size = EEPROM_SIZE,
 114         .read = eeprom_read,
 115 };
 116
 117 /* Return 0 if detection is successful, -ENODEV otherwise */
 118 static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
 119 {
 120         struct i2c_adapter *adapter = client->adapter;
 121
 122         /* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
 123            addresses 0x50-0x57, but we only care about 0x50. So decline
 124            attaching to addresses >= 0x51 on DDC buses */
 125         if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
 126                 return -ENODEV;
 127
 128         /* There are four ways we can read the EEPROM data:
 129            (1) I2C block reads (faster, but unsupported by most adapters)
 130            (2) Word reads (128% overhead)
 131            (3) Consecutive byte reads (88% overhead, unsafe)
 132            (4) Regular byte data reads (265% overhead)
 133            The third and fourth methods are not implemented by this driver
 134            because all known adapters support one of the first two. */
 135         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
 136          && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
 137                 return -ENODEV;
 138
 139         strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
 140
 141         return 0;
 142 }
 143
 144 static int eeprom_probe(struct i2c_client *client,
 145                         const struct i2c_device_id *id)
 146 {
 147         struct i2c_adapter *adapter = client->adapter;
 148         struct eeprom_data *data;
 149
 150         data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
 151                             GFP_KERNEL);
 152         if (!data)
 153                 return -ENOMEM;
 154
 155         memset(data->data, 0xff, EEPROM_SIZE);
 156         i2c_set_clientdata(client, data);
 157         mutex_init(&data->update_lock);
 158         data->nature = UNKNOWN;
 159
 160         /* Detect the Vaio nature of EEPROMs.
 161            We use the "PCG-" or "VGN-" prefix as the signature. */
 162         if (client->addr == 0x57
 163          && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 164                 char name[4];
 165
 166                 name[0] = i2c_smbus_read_byte_data(client, 0x80);
 167                 name[1] = i2c_smbus_read_byte_data(client, 0x81);
 168                 name[2] = i2c_smbus_read_byte_data(client, 0x82);
 169                 name[3] = i2c_smbus_read_byte_data(client, 0x83);
 170
 171                 if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
 172                         dev_info(&client->dev, "Vaio EEPROM detected, "
 173                                  "enabling privacy protection\n");
 174                         data->nature = VAIO;
 175                 }
 176         }
 177
 178         /* Let the users know they are using deprecated driver */
 179         dev_notice(&client->dev,
 180                    "eeprom driver is deprecated, please use at24 instead\n");
 181
 182         /* create the sysfs eeprom file */
 183         return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
 184 }
 185
 186 static int eeprom_remove(struct i2c_client *client)
 187 {
 188         sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
 189
 190         return 0;
 191 }
 192
 193 static const struct i2c_device_id eeprom_id[] = {
 194         { "eeprom", 0 },
 195         { }
 196 };
 197
 198 static struct i2c_driver eeprom_driver = {
 199         .driver = {
 200                 .name   = "eeprom",
 201         },
 202         .probe          = eeprom_probe,
 203         .remove         = eeprom_remove,
 204         .id_table       = eeprom_id,
 205
 206         .class          = I2C_CLASS_DDC | I2C_CLASS_SPD,
 207         .detect         = eeprom_detect,
 208         .address_list   = normal_i2c,
 209 };
 210
 211 module_i2c_driver(eeprom_driver);
 212
 213 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
 214                 "Philip Edelbrock <phil@netroedge.com> and "
 215                 "Greg Kroah-Hartman <greg@kroah.com>");
 216 MODULE_DESCRIPTION("I2C EEPROM driver");
 217 MODULE_LICENSE("GPL");