drivers/i2c/i2c-slave-eeprom.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * I2C slave mode EEPROM simulator
   4  *
   5  * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
   6  * Copyright (C) 2014 by Renesas Electronics Corporation
   7  *
   8  * Because most IP blocks can only detect one I2C slave address anyhow, this
   9  * driver does not support simulating EEPROM types which take more than one
  10  * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit
  11  * pointer, yet implementation is deferred until the need actually arises.
  12  */
  13
  14 /*
  15  * FIXME: What to do if only 8 bits of a 16 bit address are sent?
  16  * The ST-M24C64 sends only 0xff then. Needs verification with other
  17  * EEPROMs, though. We currently use the 8 bit as a valid address.
  18  */
  19
  20 #include <linux/bitfield.h>
  21 #include <linux/i2c.h>
  22 #include <linux/init.h>
  23 #include <linux/module.h>
  24 #include <linux/of.h>
  25 #include <linux/slab.h>
  26 #include <linux/spinlock.h>
  27 #include <linux/sysfs.h>
  28
  29 struct eeprom_data {
  30         struct bin_attribute bin;
  31         spinlock_t buffer_lock;
  32         u16 buffer_idx;
  33         u16 address_mask;
  34         u8 num_address_bytes;
  35         u8 idx_write_cnt;
  36         bool read_only;
  37         u8 buffer[];
  38 };
  39
  40 #define I2C_SLAVE_BYTELEN GENMASK(15, 0)
  41 #define I2C_SLAVE_FLAG_ADDR16 BIT(16)
  42 #define I2C_SLAVE_FLAG_RO BIT(17)
  43 #define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | (_len))
  44
  45 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
  46                                      enum i2c_slave_event event, u8 *val)
  47 {
  48         struct eeprom_data *eeprom = i2c_get_clientdata(client);
  49
  50         switch (event) {
  51         case I2C_SLAVE_WRITE_RECEIVED:
  52                 if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
  53                         if (eeprom->idx_write_cnt == 0)
  54                                 eeprom->buffer_idx = 0;
  55                         eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
  56                         eeprom->idx_write_cnt++;
  57                 } else {
  58                         if (!eeprom->read_only) {
  59                                 spin_lock(&eeprom->buffer_lock);
  60                                 eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
  61                                 spin_unlock(&eeprom->buffer_lock);
  62                         }
  63                 }
  64                 break;
  65
  66         case I2C_SLAVE_READ_PROCESSED:
  67                 /* The previous byte made it to the bus, get next one */
  68                 eeprom->buffer_idx++;
  69                 /* fallthrough */
  70         case I2C_SLAVE_READ_REQUESTED:
  71                 spin_lock(&eeprom->buffer_lock);
  72                 *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
  73                 spin_unlock(&eeprom->buffer_lock);
  74                 /*
  75                  * Do not increment buffer_idx here, because we don't know if
  76                  * this byte will be actually used. Read Linux I2C slave docs
  77                  * for details.
  78                  */
  79                 break;
  80
  81         case I2C_SLAVE_STOP:
  82         case I2C_SLAVE_WRITE_REQUESTED:
  83                 eeprom->idx_write_cnt = 0;
  84                 break;
  85
  86         default:
  87                 break;
  88         }
  89
  90         return 0;
  91 }
  92
  93 static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
  94                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
  95 {
  96         struct eeprom_data *eeprom;
  97         unsigned long flags;
  98
  99         eeprom = dev_get_drvdata(kobj_to_dev(kobj));
 100
 101         spin_lock_irqsave(&eeprom->buffer_lock, flags);
 102         memcpy(buf, &eeprom->buffer[off], count);
 103         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
 104
 105         return count;
 106 }
 107
 108 static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
 109                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
 110 {
 111         struct eeprom_data *eeprom;
 112         unsigned long flags;
 113
 114         eeprom = dev_get_drvdata(kobj_to_dev(kobj));
 115
 116         spin_lock_irqsave(&eeprom->buffer_lock, flags);
 117         memcpy(&eeprom->buffer[off], buf, count);
 118         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
 119
 120         return count;
 121 }
 122
 123 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
 124 {
 125         struct eeprom_data *eeprom;
 126         int ret;
 127         unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data);
 128         unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
 129
 130         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 131         if (!eeprom)
 132                 return -ENOMEM;
 133
 134         eeprom->idx_write_cnt = 0;
 135         eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
 136         eeprom->address_mask = size - 1;
 137         eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
 138         spin_lock_init(&eeprom->buffer_lock);
 139         i2c_set_clientdata(client, eeprom);
 140
 141         sysfs_bin_attr_init(&eeprom->bin);
 142         eeprom->bin.attr.name = "slave-eeprom";
 143         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
 144         eeprom->bin.read = i2c_slave_eeprom_bin_read;
 145         eeprom->bin.write = i2c_slave_eeprom_bin_write;
 146         eeprom->bin.size = size;
 147
 148         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
 149         if (ret)
 150                 return ret;
 151
 152         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
 153         if (ret) {
 154                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 155                 return ret;
 156         }
 157
 158         return 0;
 159 };
 160
 161 static int i2c_slave_eeprom_remove(struct i2c_client *client)
 162 {
 163         struct eeprom_data *eeprom = i2c_get_clientdata(client);
 164
 165         i2c_slave_unregister(client);
 166         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 167
 168         return 0;
 169 }
 170
 171 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 172         { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
 173         { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  I2C_SLAVE_FLAG_RO) },
 174         { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
 175         { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
 176         { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
 177         { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
 178         { }
 179 };
 180 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 181
 182 static struct i2c_driver i2c_slave_eeprom_driver = {
 183         .driver = {
 184                 .name = "i2c-slave-eeprom",
 185         },
 186         .probe = i2c_slave_eeprom_probe,
 187         .remove = i2c_slave_eeprom_remove,
 188         .id_table = i2c_slave_eeprom_id,
 189 };
 190 module_i2c_driver(i2c_slave_eeprom_driver);
 191
 192 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 193 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
 194 MODULE_LICENSE("GPL v2");