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 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)) 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_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id) 124 { 125 struct eeprom_data *eeprom; 126 int ret; 127 unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data); 128 unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data); 129 130 eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL); 131 if (!eeprom) 132 return -ENOMEM; 133 134 eeprom->idx_write_cnt = 0; 135 eeprom->num_address_bytes = flag_addr16 ? 2 : 1; 136 eeprom->address_mask = size - 1; 137 eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data); 138 spin_lock_init(&eeprom->buffer_lock); 139 i2c_set_clientdata(client, eeprom); 140 141 sysfs_bin_attr_init(&eeprom->bin); 142 eeprom->bin.attr.name = "slave-eeprom"; 143 eeprom->bin.attr.mode = S_IRUSR | S_IWUSR; 144 eeprom->bin.read = i2c_slave_eeprom_bin_read; 145 eeprom->bin.write = i2c_slave_eeprom_bin_write; 146 eeprom->bin.size = size; 147 148 ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin); 149 if (ret) 150 return ret; 151 152 ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb); 153 if (ret) { 154 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); 155 return ret; 156 } 157 158 return 0; 159 }; 160 161 static int i2c_slave_eeprom_remove(struct i2c_client *client) 162 { 163 struct eeprom_data *eeprom = i2c_get_clientdata(client); 164 165 i2c_slave_unregister(client); 166 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); 167 168 return 0; 169 } 170 171 static const struct i2c_device_id i2c_slave_eeprom_id[] = { 172 { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) }, 173 { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) }, 174 { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) }, 175 { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, 176 { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) }, 177 { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, 178 { } 179 }; 180 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id); 181 182 static struct i2c_driver i2c_slave_eeprom_driver = { 183 .driver = { 184 .name = "i2c-slave-eeprom", 185 }, 186 .probe = i2c_slave_eeprom_probe, 187 .remove = i2c_slave_eeprom_remove, 188 .id_table = i2c_slave_eeprom_id, 189 }; 190 module_i2c_driver(i2c_slave_eeprom_driver); 191 192 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>"); 193 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator"); 194 MODULE_LICENSE("GPL v2"); 195