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 #include <linux/bitfield.h>
  15 #include <linux/i2c.h>
  16 #include <linux/init.h>
  17 #include <linux/module.h>
  18 #include <linux/of.h>
  19 #include <linux/slab.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/sysfs.h>
  22
  23 struct eeprom_data {
  24         struct bin_attribute bin;
  25         spinlock_t buffer_lock;
  26         u16 buffer_idx;
  27         u16 address_mask;
  28         u8 num_address_bytes;
  29         u8 idx_write_cnt;
  30         u8 buffer[];
  31 };
  32
  33 #define I2C_SLAVE_BYTELEN GENMASK(15, 0)
  34 #define I2C_SLAVE_FLAG_ADDR16 BIT(16)
  35 #define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | (_len))
  36
  37 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
  38                                      enum i2c_slave_event event, u8 *val)
  39 {
  40         struct eeprom_data *eeprom = i2c_get_clientdata(client);
  41
  42         switch (event) {
  43         case I2C_SLAVE_WRITE_RECEIVED:
  44                 if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
  45                         if (eeprom->idx_write_cnt == 0)
  46                                 eeprom->buffer_idx = 0;
  47                         eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
  48                         eeprom->idx_write_cnt++;
  49                 } else {
  50                         spin_lock(&eeprom->buffer_lock);
  51                         eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
  52                         spin_unlock(&eeprom->buffer_lock);
  53                 }
  54                 break;
  55
  56         case I2C_SLAVE_READ_PROCESSED:
  57                 /* The previous byte made it to the bus, get next one */
  58                 eeprom->buffer_idx++;
  59                 /* fallthrough */
  60         case I2C_SLAVE_READ_REQUESTED:
  61                 spin_lock(&eeprom->buffer_lock);
  62                 *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
  63                 spin_unlock(&eeprom->buffer_lock);
  64                 /*
  65                  * Do not increment buffer_idx here, because we don't know if
  66                  * this byte will be actually used. Read Linux I2C slave docs
  67                  * for details.
  68                  */
  69                 break;
  70
  71         case I2C_SLAVE_STOP:
  72         case I2C_SLAVE_WRITE_REQUESTED:
  73                 eeprom->idx_write_cnt = 0;
  74                 break;
  75
  76         default:
  77                 break;
  78         }
  79
  80         return 0;
  81 }
  82
  83 static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
  84                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
  85 {
  86         struct eeprom_data *eeprom;
  87         unsigned long flags;
  88
  89         eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
  90
  91         spin_lock_irqsave(&eeprom->buffer_lock, flags);
  92         memcpy(buf, &eeprom->buffer[off], count);
  93         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
  94
  95         return count;
  96 }
  97
  98 static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
  99                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
 100 {
 101         struct eeprom_data *eeprom;
 102         unsigned long flags;
 103
 104         eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
 105
 106         spin_lock_irqsave(&eeprom->buffer_lock, flags);
 107         memcpy(&eeprom->buffer[off], buf, count);
 108         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
 109
 110         return count;
 111 }
 112
 113 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
 114 {
 115         struct eeprom_data *eeprom;
 116         int ret;
 117         unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data);
 118         unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
 119
 120         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 121         if (!eeprom)
 122                 return -ENOMEM;
 123
 124         eeprom->idx_write_cnt = 0;
 125         eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
 126         eeprom->address_mask = size - 1;
 127         spin_lock_init(&eeprom->buffer_lock);
 128         i2c_set_clientdata(client, eeprom);
 129
 130         sysfs_bin_attr_init(&eeprom->bin);
 131         eeprom->bin.attr.name = "slave-eeprom";
 132         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
 133         eeprom->bin.read = i2c_slave_eeprom_bin_read;
 134         eeprom->bin.write = i2c_slave_eeprom_bin_write;
 135         eeprom->bin.size = size;
 136
 137         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
 138         if (ret)
 139                 return ret;
 140
 141         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
 142         if (ret) {
 143                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 144                 return ret;
 145         }
 146
 147         return 0;
 148 };
 149
 150 static int i2c_slave_eeprom_remove(struct i2c_client *client)
 151 {
 152         struct eeprom_data *eeprom = i2c_get_clientdata(client);
 153
 154         i2c_slave_unregister(client);
 155         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 156
 157         return 0;
 158 }
 159
 160 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 161         { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
 162         { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
 163         { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
 164         { }
 165 };
 166 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 167
 168 static struct i2c_driver i2c_slave_eeprom_driver = {
 169         .driver = {
 170                 .name = "i2c-slave-eeprom",
 171         },
 172         .probe = i2c_slave_eeprom_probe,
 173         .remove = i2c_slave_eeprom_remove,
 174         .id_table = i2c_slave_eeprom_id,
 175 };
 176 module_i2c_driver(i2c_slave_eeprom_driver);
 177
 178 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 179 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
 180 MODULE_LICENSE("GPL v2");