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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * I2C slave mode EEPROM simulator4 *5 * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>6 * Copyright (C) 2014 by Renesas Electronics Corporation7 *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 than10 * 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 other16 * 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 29struct 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 45static 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 if76 * this byte will be actually used. Read Linux I2C slave docs77 * 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 93static 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 108static 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 123static 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 143static int i2c_slave_eeprom_probe(struct i2c_client *client)144{145 const struct i2c_device_id *id = i2c_client_get_device_id(client);146 struct eeprom_data *eeprom;147 int ret;148 unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1;149 unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);150 151 eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);152 if (!eeprom)153 return -ENOMEM;154 155 eeprom->num_address_bytes = flag_addr16 ? 2 : 1;156 eeprom->address_mask = size - 1;157 eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);158 spin_lock_init(&eeprom->buffer_lock);159 i2c_set_clientdata(client, eeprom);160 161 ret = i2c_slave_init_eeprom_data(eeprom, client, size);162 if (ret)163 return ret;164 165 sysfs_bin_attr_init(&eeprom->bin);166 eeprom->bin.attr.name = "slave-eeprom";167 eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;168 eeprom->bin.read = i2c_slave_eeprom_bin_read;169 eeprom->bin.write = i2c_slave_eeprom_bin_write;170 eeprom->bin.size = size;171 172 ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);173 if (ret)174 return ret;175 176 ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);177 if (ret) {178 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);179 return ret;180 }181 182 return 0;183};184 185static void i2c_slave_eeprom_remove(struct i2c_client *client)186{187 struct eeprom_data *eeprom = i2c_get_clientdata(client);188 189 i2c_slave_unregister(client);190 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);191}192 193static const struct i2c_device_id i2c_slave_eeprom_id[] = {194 { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) },195 { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) },196 { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },197 { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },198 { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },199 { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },200 { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) },201 { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },202 { }203};204MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);205 206static struct i2c_driver i2c_slave_eeprom_driver = {207 .driver = {208 .name = "i2c-slave-eeprom",209 },210 .probe = i2c_slave_eeprom_probe,211 .remove = i2c_slave_eeprom_remove,212 .id_table = i2c_slave_eeprom_id,213};214module_i2c_driver(i2c_slave_eeprom_driver);215 216MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");217MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");218MODULE_LICENSE("GPL v2");219