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

// SPDX-License-Identifier: GPL-2.0-only
/*
 * I2C slave mode EEPROM simulator
 *
 * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <[email protected]>
 * Copyright (C) 2014 by Renesas Electronics Corporation
 *
 * Because most slave IP cores can only detect one I2C slave address anyhow,
 * this driver does not support simulating EEPROM types which take more than
 * one address.
 */

/*
 * 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 <linux/bitfield.h>
#include <linux/firmware.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/sysfs.h>

struct eeprom_data { … };

#define I2C_SLAVE_BYTELEN …
#define I2C_SLAVE_FLAG_ADDR16 …
#define I2C_SLAVE_FLAG_RO …
#define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) …

static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
				     enum i2c_slave_event event, u8 *val)
{ … }

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)
{ … }

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)
{ … }

static int i2c_slave_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client,
				      unsigned int size)
{ … }

static int i2c_slave_eeprom_probe(struct i2c_client *client)
{
	const struct i2c_device_id *id = i2c_client_get_device_id(client);
	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 void i2c_slave_eeprom_remove(struct i2c_client *client)
{ … }

static const struct i2c_device_id i2c_slave_eeprom_id[] = …;
MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);

static struct i2c_driver i2c_slave_eeprom_driver = …;
module_i2c_driver(…) …;

MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;