kernel/drivers/i2c/i2c-slave-eeprom.c

   1 /*
   2  * I2C slave mode EEPROM simulator
   3  *
   4  * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
   5  * Copyright (C) 2014 by Renesas Electronics Corporation
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the
   9  * Free Software Foundation; version 2 of the License.
  10  *
  11  * Because most IP blocks can only detect one I2C slave address anyhow, this
  12  * driver does not support simulating EEPROM types which take more than one
  13  * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit
  14  * pointer, yet implementation is deferred until the need actually arises.
  15  */
  16
  17 #include <linux/i2c.h>
  18 #include <linux/init.h>
  19 #include <linux/module.h>
  20 #include <linux/of.h>
  21 #include <linux/slab.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/sysfs.h>
  24
  25 struct eeprom_data {
  26         struct bin_attribute bin;
  27         bool first_write;
  28         spinlock_t buffer_lock;
  29         u8 buffer_idx;
  30         u8 buffer[];
  31 };
  32
  33 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
  34                                      enum i2c_slave_event event, u8 *val)
  35 {
  36         struct eeprom_data *eeprom = i2c_get_clientdata(client);
  37
  38         switch (event) {
  39         case I2C_SLAVE_WRITE_RECEIVED:
  40                 if (eeprom->first_write) {
  41                         eeprom->buffer_idx = *val;
  42                         eeprom->first_write = false;
  43                 } else {
  44                         spin_lock(&eeprom->buffer_lock);
  45                         eeprom->buffer[eeprom->buffer_idx++] = *val;
  46                         spin_unlock(&eeprom->buffer_lock);
  47                 }
  48                 break;
  49
  50         case I2C_SLAVE_READ_PROCESSED:
  51                 /* The previous byte made it to the bus, get next one */
  52                 eeprom->buffer_idx++;
  53                 /* fallthrough */
  54         case I2C_SLAVE_READ_REQUESTED:
  55                 spin_lock(&eeprom->buffer_lock);
  56                 *val = eeprom->buffer[eeprom->buffer_idx];
  57                 spin_unlock(&eeprom->buffer_lock);
  58                 /*
  59                  * Do not increment buffer_idx here, because we don't know if
  60                  * this byte will be actually used. Read Linux I2C slave docs
  61                  * for details.
  62                  */
  63                 break;
  64
  65         case I2C_SLAVE_STOP:
  66         case I2C_SLAVE_WRITE_REQUESTED:
  67                 eeprom->first_write = true;
  68                 break;
  69
  70         default:
  71                 break;
  72         }
  73
  74         return 0;
  75 }
  76
  77 static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
  78                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
  79 {
  80         struct eeprom_data *eeprom;
  81         unsigned long flags;
  82
  83         if (off + count > attr->size)
  84                 return -EFBIG;
  85
  86         eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
  87
  88         spin_lock_irqsave(&eeprom->buffer_lock, flags);
  89         memcpy(buf, &eeprom->buffer[off], count);
  90         spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
  91
  92         return count;
  93 }
  94
  95 static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
  96                 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
  97 {
  98         struct eeprom_data *eeprom;
  99         unsigned long flags;
 100
 101         if (off + count > attr->size)
 102                 return -EFBIG;
 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 size = id->driver_data;
 118
 119         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 120         if (!eeprom)
 121                 return -ENOMEM;
 122
 123         eeprom->first_write = true;
 124         spin_lock_init(&eeprom->buffer_lock);
 125         i2c_set_clientdata(client, eeprom);
 126
 127         sysfs_bin_attr_init(&eeprom->bin);
 128         eeprom->bin.attr.name = "slave-eeprom";
 129         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
 130         eeprom->bin.read = i2c_slave_eeprom_bin_read;
 131         eeprom->bin.write = i2c_slave_eeprom_bin_write;
 132         eeprom->bin.size = size;
 133
 134         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
 135         if (ret)
 136                 return ret;
 137
 138         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
 139         if (ret) {
 140                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 141                 return ret;
 142         }
 143
 144         return 0;
 145 };
 146
 147 static int i2c_slave_eeprom_remove(struct i2c_client *client)
 148 {
 149         struct eeprom_data *eeprom = i2c_get_clientdata(client);
 150
 151         i2c_slave_unregister(client);
 152         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 153
 154         return 0;
 155 }
 156
 157 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 158         { "slave-24c02", 2048 / 8 },
 159         { }
 160 };
 161 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 162
 163 static struct i2c_driver i2c_slave_eeprom_driver = {
 164         .driver = {
 165                 .name = "i2c-slave-eeprom",
 166                 .owner = THIS_MODULE,
 167         },
 168         .probe = i2c_slave_eeprom_probe,
 169         .remove = i2c_slave_eeprom_remove,
 170         .id_table = i2c_slave_eeprom_id,
 171 };
 172 module_i2c_driver(i2c_slave_eeprom_driver);
 173
 174 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 175 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
 176 MODULE_LICENSE("GPL v2");