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 slave IP cores can only detect one I2C slave address anyhow,
   9  * this driver does not support simulating EEPROM types which take more than
  10  * one address.
  11  */
  12
  13 /*
  14  * FIXME: What to do if only 8 bits of a 16 bit address are sent?
  15  * The ST-M24C64 sends only 0xff then. Needs verification with other
  16  * EEPROMs, though. We currently use the 8 bit as a valid address.
  17  */
  18
  19 #include <linux/bitfield.h>
  20 #include <linux/firmware.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) - 1))
  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_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client,
 124                                       unsigned int size)
 125 {
 126         const struct firmware *fw;
 127         const char *eeprom_data;
 128         int ret = device_property_read_string(&client->dev, "firmware-name", &eeprom_data);
 129
 130         if (!ret) {
 131                 ret = request_firmware_into_buf(&fw, eeprom_data, &client->dev,
 132                                                 eeprom->buffer, size);
 133                 if (ret)
 134                         return ret;
 135                 release_firmware(fw);
 136         } else {
 137                 /* An empty eeprom typically has all bits set to 1 */
 138                 memset(eeprom->buffer, 0xff, size);
 139         }
 140         return 0;
 141 }
 142
 143 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
 144 {
 145         struct eeprom_data *eeprom;
 146         int ret;
 147         unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1;
 148         unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
 149
 150         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 151         if (!eeprom)
 152                 return -ENOMEM;
 153
 154         eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
 155         eeprom->address_mask = size - 1;
 156         eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
 157         spin_lock_init(&eeprom->buffer_lock);
 158         i2c_set_clientdata(client, eeprom);
 159
 160         ret = i2c_slave_init_eeprom_data(eeprom, client, size);
 161         if (ret)
 162                 return ret;
 163
 164         sysfs_bin_attr_init(&eeprom->bin);
 165         eeprom->bin.attr.name = "slave-eeprom";
 166         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
 167         eeprom->bin.read = i2c_slave_eeprom_bin_read;
 168         eeprom->bin.write = i2c_slave_eeprom_bin_write;
 169         eeprom->bin.size = size;
 170
 171         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
 172         if (ret)
 173                 return ret;
 174
 175         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
 176         if (ret) {
 177                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 178                 return ret;
 179         }
 180
 181         return 0;
 182 };
 183
 184 static int i2c_slave_eeprom_remove(struct i2c_client *client)
 185 {
 186         struct eeprom_data *eeprom = i2c_get_clientdata(client);
 187
 188         i2c_slave_unregister(client);
 189         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
 190
 191         return 0;
 192 }
 193
 194 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 195         { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
 196         { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  I2C_SLAVE_FLAG_RO) },
 197         { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
 198         { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
 199         { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
 200         { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
 201         { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) },
 202         { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
 203         { }
 204 };
 205 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 206
 207 static struct i2c_driver i2c_slave_eeprom_driver = {
 208         .driver = {
 209                 .name = "i2c-slave-eeprom",
 210         },
 211         .probe = i2c_slave_eeprom_probe,
 212         .remove = i2c_slave_eeprom_remove,
 213         .id_table = i2c_slave_eeprom_id,
 214 };
 215 module_i2c_driver(i2c_slave_eeprom_driver);
 216
 217 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 218 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
 219 MODULE_LICENSE("GPL v2");