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         u8 buffer[];
  37 };
  38
  39 #define I2C_SLAVE_BYTELEN GENMASK(15, 0)
  40 #define I2C_SLAVE_FLAG_ADDR16 BIT(16)
  41 #define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | (_len))
  42
  43 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
  44                                      enum i2c_slave_event event, u8 *val)
  45 {
  46         struct eeprom_data *eeprom = i2c_get_clientdata(client);
  47
  48         switch (event) {
  49         case I2C_SLAVE_WRITE_RECEIVED:
  50                 if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
  51                         if (eeprom->idx_write_cnt == 0)
  52                                 eeprom->buffer_idx = 0;
  53                         eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
  54                         eeprom->idx_write_cnt++;
  55                 } else {
  56                         spin_lock(&eeprom->buffer_lock);
  57                         eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
  58                         spin_unlock(&eeprom->buffer_lock);
  59                 }
  60                 break;
  61
  62         case I2C_SLAVE_READ_PROCESSED:
  63                 /* The previous byte made it to the bus, get next one */
  64                 eeprom->buffer_idx++;
  65                 /* fallthrough */
  66         case I2C_SLAVE_READ_REQUESTED:
  67                 spin_lock(&eeprom->buffer_lock);
  68                 *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
  69                 spin_unlock(&eeprom->buffer_lock);
  70                 /*
  71                  * Do not increment buffer_idx here, because we don't know if
  72                  * this byte will be actually used. Read Linux I2C slave docs
  73                  * for details.
  74                  */
  75                 break;
  76
  77         case I2C_SLAVE_STOP:
  78         case I2C_SLAVE_WRITE_REQUESTED:
  79                 eeprom->idx_write_cnt = 0;
  80                 break;
  81
  82         default:
  83                 break;
  84         }
  85
  86         return 0;
  87 }
  88
  89 static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
  90                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
  91 {
  92         struct eeprom_data *eeprom;
  93         unsigned long flags;
  94
  95         eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
  96
  97         spin_lock_irqsave(&eeprom->buffer_lock, flags);
  98         memcpy(buf, &eeprom->buffer[off], count);
  99         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
 100
 101         return count;
 102 }
 103
 104 static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
 105                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
 106 {
 107         struct eeprom_data *eeprom;
 108         unsigned long flags;
 109
 110         eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
 111
 112         spin_lock_irqsave(&eeprom->buffer_lock, flags);
 113         memcpy(&eeprom->buffer[off], buf, count);
 114         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
 115
 116         return count;
 117 }
 118
 119 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
 120 {
 121         struct eeprom_data *eeprom;
 122         int ret;
 123         unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data);
 124         unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
 125
 126         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 127         if (!eeprom)
 128                 return -ENOMEM;
 129
 130         eeprom->idx_write_cnt = 0;
 131         eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
 132         eeprom->address_mask = size - 1;
 133         spin_lock_init(&eeprom->buffer_lock);
 134         i2c_set_clientdata(client, eeprom);
 135
 136         sysfs_bin_attr_init(&eeprom->bin);
 137         eeprom->bin.attr.name = "slave-eeprom";
 138         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
 139         eeprom->bin.read = i2c_slave_eeprom_bin_read;
 140         eeprom->bin.write = i2c_slave_eeprom_bin_write;
 141         eeprom->bin.size = size;
 142
 143         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
 144         if (ret)
 145                 return ret;
 146
 147         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
 148         if (ret) {
 149                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 150                 return ret;
 151         }
 152
 153         return 0;
 154 };
 155
 156 static int i2c_slave_eeprom_remove(struct i2c_client *client)
 157 {
 158         struct eeprom_data *eeprom = i2c_get_clientdata(client);
 159
 160         i2c_slave_unregister(client);
 161         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 162
 163         return 0;
 164 }
 165
 166 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 167         { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
 168         { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
 169         { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
 170         { }
 171 };
 172 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 173
 174 static struct i2c_driver i2c_slave_eeprom_driver = {
 175         .driver = {
 176                 .name = "i2c-slave-eeprom",
 177         },
 178         .probe = i2c_slave_eeprom_probe,
 179         .remove = i2c_slave_eeprom_remove,
 180         .id_table = i2c_slave_eeprom_id,
 181 };
 182 module_i2c_driver(i2c_slave_eeprom_driver);
 183
 184 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 185 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
 186 MODULE_LICENSE("GPL v2");