1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Linux I2C core slave support code
  4 *
  5 * Copyright (C) 2014 by Wolfram Sang <wsa@sang-engineering.com>
  6 */
  7
  8#include <dt-bindings/i2c/i2c.h>
  9#include <linux/acpi.h>
 10#include <linux/device.h>
 11#include <linux/err.h>
 12#include <linux/i2c.h>
 13#include <linux/of.h>
 14
 15#include "i2c-core.h"
 16
 17int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 18{
 19	int ret;
 20
 21	if (!client || !slave_cb) {
 22		WARN(1, "insufficient data\n");
 23		return -EINVAL;
 24	}
 25
 26	if (!(client->flags & I2C_CLIENT_SLAVE))
 27		dev_warn(&client->dev, "%s: client slave flag not set. You might see address collisions\n",
 28			 __func__);
 29
 30	if (!(client->flags & I2C_CLIENT_TEN)) {
 31		/* Enforce stricter address checking */
 32		ret = i2c_check_7bit_addr_validity_strict(client->addr);
 33		if (ret) {
 34			dev_err(&client->dev, "%s: invalid address\n", __func__);
 35			return ret;
 36		}
 37	}
 38
 39	if (!client->adapter->algo->reg_slave) {
 40		dev_err(&client->dev, "%s: not supported by adapter\n", __func__);
 41		return -EOPNOTSUPP;
 42	}
 43
 44	client->slave_cb = slave_cb;
 45
 46	i2c_lock_bus(client->adapter, I2C_LOCK_ROOT_ADAPTER);
 47	ret = client->adapter->algo->reg_slave(client);
 48	i2c_unlock_bus(client->adapter, I2C_LOCK_ROOT_ADAPTER);
 49
 50	if (ret) {
 51		client->slave_cb = NULL;
 52		dev_err(&client->dev, "%s: adapter returned error %d\n", __func__, ret);
 53	}
 54
 55	return ret;
 56}
 57EXPORT_SYMBOL_GPL(i2c_slave_register);
 58
 59int i2c_slave_unregister(struct i2c_client *client)
 60{
 61	int ret;
 62
 63	if (!client->adapter->algo->unreg_slave) {
 64		dev_err(&client->dev, "%s: not supported by adapter\n", __func__);
 65		return -EOPNOTSUPP;
 66	}
 67
 68	i2c_lock_bus(client->adapter, I2C_LOCK_ROOT_ADAPTER);
 69	ret = client->adapter->algo->unreg_slave(client);
 70	i2c_unlock_bus(client->adapter, I2C_LOCK_ROOT_ADAPTER);
 71
 72	if (ret == 0)
 73		client->slave_cb = NULL;
 74	else
 75		dev_err(&client->dev, "%s: adapter returned error %d\n", __func__, ret);
 76
 77	return ret;
 78}
 79EXPORT_SYMBOL_GPL(i2c_slave_unregister);
 80
 81/**
 82 * i2c_detect_slave_mode - detect operation mode
 83 * @dev: The device owning the bus
 84 *
 85 * This checks the device nodes for an I2C slave by checking the address
 86 * used in the reg property. If the address match the I2C_OWN_SLAVE_ADDRESS
 87 * flag this means the device is configured to act as a I2C slave and it will
 88 * be listening at that address.
 89 *
 90 * Returns true if an I2C own slave address is detected, otherwise returns
 91 * false.
 92 */
 93bool i2c_detect_slave_mode(struct device *dev)
 94{
 95	if (IS_BUILTIN(CONFIG_OF) && dev->of_node) {
 96		struct device_node *child;
 97		u32 reg;
 98
 99		for_each_child_of_node(dev->of_node, child) {
100			of_property_read_u32(child, "reg", &reg);
101			if (reg & I2C_OWN_SLAVE_ADDRESS) {
102				of_node_put(child);
103				return true;
104			}
105		}
106	} else if (IS_BUILTIN(CONFIG_ACPI) && ACPI_HANDLE(dev)) {
107		dev_dbg(dev, "ACPI slave is not supported yet\n");
108	}
109	return false;
110}
111EXPORT_SYMBOL_GPL(i2c_detect_slave_mode);