// SPDX-License-Identifier: GPL-2.0-only /* * I2C slave mode EEPROM simulator * * Copyright (C) 2014 by Wolfram Sang, Sang Engineering * Copyright (C) 2014 by Renesas Electronics Corporation * * Because most IP blocks can only detect one I2C slave address anyhow, this * driver does not support simulating EEPROM types which take more than one * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit * pointer, yet implementation is deferred until the need actually arises. */ /* * FIXME: What to do if only 8 bits of a 16 bit address are sent? * The ST-M24C64 sends only 0xff then. Needs verification with other * EEPROMs, though. We currently use the 8 bit as a valid address. */ #include #include #include #include #include #include #include #include #include struct eeprom_data { struct bin_attribute bin; spinlock_t buffer_lock; u16 buffer_idx; u16 address_mask; u8 num_address_bytes; u8 idx_write_cnt; bool read_only; u8 buffer[]; }; #define I2C_SLAVE_BYTELEN GENMASK(15, 0) #define I2C_SLAVE_FLAG_ADDR16 BIT(16) #define I2C_SLAVE_FLAG_RO BIT(17) #define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | ((_len) - 1)) static int i2c_slave_eeprom_slave_cb(struct i2c_client *client, enum i2c_slave_event event, u8 *val) { struct eeprom_data *eeprom = i2c_get_clientdata(client); switch (event) { case I2C_SLAVE_WRITE_RECEIVED: if (eeprom->idx_write_cnt < eeprom->num_address_bytes) { if (eeprom->idx_write_cnt == 0) eeprom->buffer_idx = 0; eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8); eeprom->idx_write_cnt++; } else { if (!eeprom->read_only) { spin_lock(&eeprom->buffer_lock); eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val; spin_unlock(&eeprom->buffer_lock); } } break; case I2C_SLAVE_READ_PROCESSED: /* The previous byte made it to the bus, get next one */ eeprom->buffer_idx++; /* fallthrough */ case I2C_SLAVE_READ_REQUESTED: spin_lock(&eeprom->buffer_lock); *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask]; spin_unlock(&eeprom->buffer_lock); /* * Do not increment buffer_idx here, because we don't know if * this byte will be actually used. Read Linux I2C slave docs * for details. */ break; case I2C_SLAVE_STOP: case I2C_SLAVE_WRITE_REQUESTED: eeprom->idx_write_cnt = 0; break; default: break; } return 0; } static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) { struct eeprom_data *eeprom; unsigned long flags; eeprom = dev_get_drvdata(kobj_to_dev(kobj)); spin_lock_irqsave(&eeprom->buffer_lock, flags); memcpy(buf, &eeprom->buffer[off], count); spin_unlock_irqrestore(&eeprom->buffer_lock, flags); return count; } static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) { struct eeprom_data *eeprom; unsigned long flags; eeprom = dev_get_drvdata(kobj_to_dev(kobj)); spin_lock_irqsave(&eeprom->buffer_lock, flags); memcpy(&eeprom->buffer[off], buf, count); spin_unlock_irqrestore(&eeprom->buffer_lock, flags); return count; } static int i2c_slave_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client, unsigned int size) { const struct firmware *fw; const char *eeprom_data; int ret = device_property_read_string(&client->dev, "firmware-name", &eeprom_data); if (!ret) { ret = request_firmware_into_buf(&fw, eeprom_data, &client->dev, eeprom->buffer, size); if (ret) return ret; release_firmware(fw); } else { /* An empty eeprom typically has all bits set to 1 */ memset(eeprom->buffer, 0xff, size); } return 0; } static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id) { struct eeprom_data *eeprom; int ret; unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1; unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data); eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL); if (!eeprom) return -ENOMEM; eeprom->num_address_bytes = flag_addr16 ? 2 : 1; eeprom->address_mask = size - 1; eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data); spin_lock_init(&eeprom->buffer_lock); i2c_set_clientdata(client, eeprom); ret = i2c_slave_init_eeprom_data(eeprom, client, size); if (ret) return ret; sysfs_bin_attr_init(&eeprom->bin); eeprom->bin.attr.name = "slave-eeprom"; eeprom->bin.attr.mode = S_IRUSR | S_IWUSR; eeprom->bin.read = i2c_slave_eeprom_bin_read; eeprom->bin.write = i2c_slave_eeprom_bin_write; eeprom->bin.size = size; ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin); if (ret) return ret; ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb); if (ret) { sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); return ret; } return 0; }; static int i2c_slave_eeprom_remove(struct i2c_client *client) { struct eeprom_data *eeprom = i2c_get_clientdata(client); i2c_slave_unregister(client); sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); return 0; } static const struct i2c_device_id i2c_slave_eeprom_id[] = { { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) }, { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) }, { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) }, { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) }, { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) }, { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, { } }; MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id); static struct i2c_driver i2c_slave_eeprom_driver = { .driver = { .name = "i2c-slave-eeprom", }, .probe = i2c_slave_eeprom_probe, .remove = i2c_slave_eeprom_remove, .id_table = i2c_slave_eeprom_id, }; module_i2c_driver(i2c_slave_eeprom_driver); MODULE_AUTHOR("Wolfram Sang "); MODULE_DESCRIPTION("I2C slave mode EEPROM simulator"); MODULE_LICENSE("GPL v2");