/* i2c-core.c - a device driver for the iic-bus interface		     */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-99 Simon G. Vogl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.			     */
/* ------------------------------------------------------------------------- */

/* With some changes from KyÜsti Mälkki <kmalkki@cc.hut.fi>.
   All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
   SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
   Jean Delvare <jdelvare@suse.de>
   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
   Michael Lawnick <michael.lawnick.ext@nsn.com>
   OF support is copyright (c) 2008 Jochen Friedrich <jochen@scram.de>
   (based on a previous patch from Jon Smirl <jonsmirl@gmail.com>) and
   (c) 2013  Wolfram Sang <wsa@the-dreams.de>
   I2C ACPI code Copyright (C) 2014 Intel Corp
   Author: Lan Tianyu <tianyu.lan@intel.com>
   I2C slave support (c) 2014 by Wolfram Sang <wsa@sang-engineering.com>
 */

#define pr_fmt(fmt) "i2c-core: " fmt

#include <dt-bindings/i2c/i2c.h>
#include <asm/uaccess.h>
#include <linux/acpi.h>
#include <linux/clk/clk-conf.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/hardirq.h>
#include <linux/i2c.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/irqflags.h>
#include <linux/jump_label.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/pm_wakeirq.h>
#include <linux/property.h>
#include <linux/rwsem.h>
#include <linux/slab.h>

#include "i2c-core.h"

#define CREATE_TRACE_POINTS
#include <trace/events/i2c.h>

#define I2C_ADDR_OFFSET_TEN_BIT	0xa000
#define I2C_ADDR_OFFSET_SLAVE	0x1000

/* core_lock protects i2c_adapter_idr, and guarantees
   that device detection, deletion of detected devices, and attach_adapter
   calls are serialized */
static DEFINE_MUTEX(core_lock);
static DEFINE_IDR(i2c_adapter_idr);

static struct device_type i2c_client_type;
static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);

static struct static_key i2c_trace_msg = STATIC_KEY_INIT_FALSE;
static bool is_registered;

void i2c_transfer_trace_reg(void)
{
	static_key_slow_inc(&i2c_trace_msg);
}

void i2c_transfer_trace_unreg(void)
{
	static_key_slow_dec(&i2c_trace_msg);
}

#if defined(CONFIG_ACPI)
struct acpi_i2c_handler_data {
	struct acpi_connection_info info;
	struct i2c_adapter *adapter;
};

struct gsb_buffer {
	u8	status;
	u8	len;
	union {
		u16	wdata;
		u8	bdata;
		u8	data[0];
	};
} __packed;

struct acpi_i2c_lookup {
	struct i2c_board_info *info;
	acpi_handle adapter_handle;
	acpi_handle device_handle;
};

static int acpi_i2c_fill_info(struct acpi_resource *ares, void *data)
{
	struct acpi_i2c_lookup *lookup = data;
	struct i2c_board_info *info = lookup->info;
	struct acpi_resource_i2c_serialbus *sb;
	acpi_status status;

	if (info->addr || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
		return 1;

	sb = &ares->data.i2c_serial_bus;
	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C)
		return 1;

	status = acpi_get_handle(lookup->device_handle,
				 sb->resource_source.string_ptr,
				 &lookup->adapter_handle);
	if (!ACPI_SUCCESS(status))
		return 1;

	info->addr = sb->slave_address;
	if (sb->access_mode == ACPI_I2C_10BIT_MODE)
		info->flags |= I2C_CLIENT_TEN;

	return 1;
}

static int acpi_i2c_get_info(struct acpi_device *adev,
			     struct i2c_board_info *info,
			     acpi_handle *adapter_handle)
{
	struct list_head resource_list;
	struct resource_entry *entry;
	struct acpi_i2c_lookup lookup;
	int ret;

	if (acpi_bus_get_status(adev) || !adev->status.present ||
	    acpi_device_enumerated(adev))
		return -EINVAL;

	memset(info, 0, sizeof(*info));
	info->fwnode = acpi_fwnode_handle(adev);

	memset(&lookup, 0, sizeof(lookup));
	lookup.device_handle = acpi_device_handle(adev);
	lookup.info = info;

	/* Look up for I2cSerialBus resource */
	INIT_LIST_HEAD(&resource_list);
	ret = acpi_dev_get_resources(adev, &resource_list,
				     acpi_i2c_fill_info, &lookup);
	acpi_dev_free_resource_list(&resource_list);

	if (ret < 0 || !info->addr)
		return -EINVAL;

	*adapter_handle = lookup.adapter_handle;

	/* Then fill IRQ number if any */
	ret = acpi_dev_get_resources(adev, &resource_list, NULL, NULL);
	if (ret < 0)
		return -EINVAL;

	resource_list_for_each_entry(entry, &resource_list) {
		if (resource_type(entry->res) == IORESOURCE_IRQ) {
			info->irq = entry->res->start;
			break;
		}
	}

	acpi_dev_free_resource_list(&resource_list);

	strlcpy(info->type, dev_name(&adev->dev), sizeof(info->type));

	return 0;
}

static void acpi_i2c_register_device(struct i2c_adapter *adapter,
				     struct acpi_device *adev,
				     struct i2c_board_info *info)
{
	adev->power.flags.ignore_parent = true;
	acpi_device_set_enumerated(adev);

	if (!i2c_new_device(adapter, info)) {
		adev->power.flags.ignore_parent = false;
		dev_err(&adapter->dev,
			"failed to add I2C device %s from ACPI\n",
			dev_name(&adev->dev));
	}
}

static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
				       void *data, void **return_value)
{
	struct i2c_adapter *adapter = data;
	struct acpi_device *adev;
	acpi_handle adapter_handle;
	struct i2c_board_info info;

	if (acpi_bus_get_device(handle, &adev))
		return AE_OK;

	if (acpi_i2c_get_info(adev, &info, &adapter_handle))
		return AE_OK;

	if (adapter_handle != ACPI_HANDLE(&adapter->dev))
		return AE_OK;

	acpi_i2c_register_device(adapter, adev, &info);

	return AE_OK;
}

#define ACPI_I2C_MAX_SCAN_DEPTH 32

/**
 * acpi_i2c_register_devices - enumerate I2C slave devices behind adapter
 * @adap: pointer to adapter
 *
 * Enumerate all I2C slave devices behind this adapter by walking the ACPI
 * namespace. When a device is found it will be added to the Linux device
 * model and bound to the corresponding ACPI handle.
 */
static void acpi_i2c_register_devices(struct i2c_adapter *adap)
{
	acpi_status status;

	if (!has_acpi_companion(&adap->dev))
		return;

	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
				     ACPI_I2C_MAX_SCAN_DEPTH,
				     acpi_i2c_add_device, NULL,
				     adap, NULL);
	if (ACPI_FAILURE(status))
		dev_warn(&adap->dev, "failed to enumerate I2C slaves\n");
}

static int acpi_i2c_match_adapter(struct device *dev, void *data)
{
	struct i2c_adapter *adapter = i2c_verify_adapter(dev);

	if (!adapter)
		return 0;

	return ACPI_HANDLE(dev) == (acpi_handle)data;
}

static int acpi_i2c_match_device(struct device *dev, void *data)
{
	return ACPI_COMPANION(dev) == data;
}

static struct i2c_adapter *acpi_i2c_find_adapter_by_handle(acpi_handle handle)
{
	struct device *dev;

	dev = bus_find_device(&i2c_bus_type, NULL, handle,
			      acpi_i2c_match_adapter);
	return dev ? i2c_verify_adapter(dev) : NULL;
}

static struct i2c_client *acpi_i2c_find_client_by_adev(struct acpi_device *adev)
{
	struct device *dev;

	dev = bus_find_device(&i2c_bus_type, NULL, adev, acpi_i2c_match_device);
	return dev ? i2c_verify_client(dev) : NULL;
}

static int acpi_i2c_notify(struct notifier_block *nb, unsigned long value,
			   void *arg)
{
	struct acpi_device *adev = arg;
	struct i2c_board_info info;
	acpi_handle adapter_handle;
	struct i2c_adapter *adapter;
	struct i2c_client *client;

	switch (value) {
	case ACPI_RECONFIG_DEVICE_ADD:
		if (acpi_i2c_get_info(adev, &info, &adapter_handle))
			break;

		adapter = acpi_i2c_find_adapter_by_handle(adapter_handle);
		if (!adapter)
			break;

		acpi_i2c_register_device(adapter, adev, &info);
		break;
	case ACPI_RECONFIG_DEVICE_REMOVE:
		if (!acpi_device_enumerated(adev))
			break;

		client = acpi_i2c_find_client_by_adev(adev);
		if (!client)
			break;

		i2c_unregister_device(client);
		put_device(&client->dev);
		break;
	}

	return NOTIFY_OK;
}

static struct notifier_block i2c_acpi_notifier = {
	.notifier_call = acpi_i2c_notify,
};
#else /* CONFIG_ACPI */
static inline void acpi_i2c_register_devices(struct i2c_adapter *adap) { }
extern struct notifier_block i2c_acpi_notifier;
#endif /* CONFIG_ACPI */

#ifdef CONFIG_ACPI_I2C_OPREGION
static int acpi_gsb_i2c_read_bytes(struct i2c_client *client,
		u8 cmd, u8 *data, u8 data_len)
{

	struct i2c_msg msgs[2];
	int ret;
	u8 *buffer;

	buffer = kzalloc(data_len, GFP_KERNEL);
	if (!buffer)
		return AE_NO_MEMORY;

	msgs[0].addr = client->addr;
	msgs[0].flags = client->flags;
	msgs[0].len = 1;
	msgs[0].buf = &cmd;

	msgs[1].addr = client->addr;
	msgs[1].flags = client->flags | I2C_M_RD;
	msgs[1].len = data_len;
	msgs[1].buf = buffer;

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret < 0)
		dev_err(&client->adapter->dev, "i2c read failed\n");
	else
		memcpy(data, buffer, data_len);

	kfree(buffer);
	return ret;
}

static int acpi_gsb_i2c_write_bytes(struct i2c_client *client,
		u8 cmd, u8 *data, u8 data_len)
{

	struct i2c_msg msgs[1];
	u8 *buffer;
	int ret = AE_OK;

	buffer = kzalloc(data_len + 1, GFP_KERNEL);
	if (!buffer)
		return AE_NO_MEMORY;

	buffer[0] = cmd;
	memcpy(buffer + 1, data, data_len);

	msgs[0].addr = client->addr;
	msgs[0].flags = client->flags;
	msgs[0].len = data_len + 1;
	msgs[0].buf = buffer;

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret < 0)
		dev_err(&client->adapter->dev, "i2c write failed\n");

	kfree(buffer);
	return ret;
}

static acpi_status
acpi_i2c_space_handler(u32 function, acpi_physical_address command,
			u32 bits, u64 *value64,
			void *handler_context, void *region_context)
{
	struct gsb_buffer *gsb = (struct gsb_buffer *)value64;
	struct acpi_i2c_handler_data *data = handler_context;
	struct acpi_connection_info *info = &data->info;
	struct acpi_resource_i2c_serialbus *sb;
	struct i2c_adapter *adapter = data->adapter;
	struct i2c_client *client;
	struct acpi_resource *ares;
	u32 accessor_type = function >> 16;
	u8 action = function & ACPI_IO_MASK;
	acpi_status ret;
	int status;

	ret = acpi_buffer_to_resource(info->connection, info->length, &ares);
	if (ACPI_FAILURE(ret))
		return ret;

	client = kzalloc(sizeof(*client), GFP_KERNEL);
	if (!client) {
		ret = AE_NO_MEMORY;
		goto err;
	}

	if (!value64 || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS) {
		ret = AE_BAD_PARAMETER;
		goto err;
	}

	sb = &ares->data.i2c_serial_bus;
	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C) {
		ret = AE_BAD_PARAMETER;
		goto err;
	}

	client->adapter = adapter;
	client->addr = sb->slave_address;

	if (sb->access_mode == ACPI_I2C_10BIT_MODE)
		client->flags |= I2C_CLIENT_TEN;

	switch (accessor_type) {
	case ACPI_GSB_ACCESS_ATTRIB_SEND_RCV:
		if (action == ACPI_READ) {
			status = i2c_smbus_read_byte(client);
			if (status >= 0) {
				gsb->bdata = status;
				status = 0;
			}
		} else {
			status = i2c_smbus_write_byte(client, gsb->bdata);
		}
		break;

	case ACPI_GSB_ACCESS_ATTRIB_BYTE:
		if (action == ACPI_READ) {
			status = i2c_smbus_read_byte_data(client, command);
			if (status >= 0) {
				gsb->bdata = status;
				status = 0;
			}
		} else {
			status = i2c_smbus_write_byte_data(client, command,
					gsb->bdata);
		}
		break;

	case ACPI_GSB_ACCESS_ATTRIB_WORD:
		if (action == ACPI_READ) {
			status = i2c_smbus_read_word_data(client, command);
			if (status >= 0) {
				gsb->wdata = status;
				status = 0;
			}
		} else {
			status = i2c_smbus_write_word_data(client, command,
					gsb->wdata);
		}
		break;

	case ACPI_GSB_ACCESS_ATTRIB_BLOCK:
		if (action == ACPI_READ) {
			status = i2c_smbus_read_block_data(client, command,
					gsb->data);
			if (status >= 0) {
				gsb->len = status;
				status = 0;
			}
		} else {
			status = i2c_smbus_write_block_data(client, command,
					gsb->len, gsb->data);
		}
		break;

	case ACPI_GSB_ACCESS_ATTRIB_MULTIBYTE:
		if (action == ACPI_READ) {
			status = acpi_gsb_i2c_read_bytes(client, command,
					gsb->data, info->access_length);
			if (status > 0)
				status = 0;
		} else {
			status = acpi_gsb_i2c_write_bytes(client, command,
					gsb->data, info->access_length);
		}
		break;

	default:
		dev_warn(&adapter->dev, "protocol 0x%02x not supported for client 0x%02x\n",
			 accessor_type, client->addr);
		ret = AE_BAD_PARAMETER;
		goto err;
	}

	gsb->status = status;

 err:
	kfree(client);
	ACPI_FREE(ares);
	return ret;
}


static int acpi_i2c_install_space_handler(struct i2c_adapter *adapter)
{
	acpi_handle handle;
	struct acpi_i2c_handler_data *data;
	acpi_status status;

	if (!adapter->dev.parent)
		return -ENODEV;

	handle = ACPI_HANDLE(adapter->dev.parent);

	if (!handle)
		return -ENODEV;

	data = kzalloc(sizeof(struct acpi_i2c_handler_data),
			    GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->adapter = adapter;
	status = acpi_bus_attach_private_data(handle, (void *)data);
	if (ACPI_FAILURE(status)) {
		kfree(data);
		return -ENOMEM;
	}

	status = acpi_install_address_space_handler(handle,
				ACPI_ADR_SPACE_GSBUS,
				&acpi_i2c_space_handler,
				NULL,
				data);
	if (ACPI_FAILURE(status)) {
		dev_err(&adapter->dev, "Error installing i2c space handler\n");
		acpi_bus_detach_private_data(handle);
		kfree(data);
		return -ENOMEM;
	}

	acpi_walk_dep_device_list(handle);
	return 0;
}

static void acpi_i2c_remove_space_handler(struct i2c_adapter *adapter)
{
	acpi_handle handle;
	struct acpi_i2c_handler_data *data;
	acpi_status status;

	if (!adapter->dev.parent)
		return;

	handle = ACPI_HANDLE(adapter->dev.parent);

	if (!handle)
		return;

	acpi_remove_address_space_handler(handle,
				ACPI_ADR_SPACE_GSBUS,
				&acpi_i2c_space_handler);

	status = acpi_bus_get_private_data(handle, (void **)&data);
	if (ACPI_SUCCESS(status))
		kfree(data);

	acpi_bus_detach_private_data(handle);
}
#else /* CONFIG_ACPI_I2C_OPREGION */
static inline void acpi_i2c_remove_space_handler(struct i2c_adapter *adapter)
{ }

static inline int acpi_i2c_install_space_handler(struct i2c_adapter *adapter)
{ return 0; }
#endif /* CONFIG_ACPI_I2C_OPREGION */

/* ------------------------------------------------------------------------- */

static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
						const struct i2c_client *client)
{
	while (id->name[0]) {
		if (strcmp(client->name, id->name) == 0)
			return id;
		id++;
	}
	return NULL;
}

static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;

	if (!client)
		return 0;

	/* Attempt an OF style match */
	if (of_driver_match_device(dev, drv))
		return 1;

	/* Then ACPI style match */
	if (acpi_driver_match_device(dev, drv))
		return 1;

	driver = to_i2c_driver(drv);
	/* match on an id table if there is one */
	if (driver->id_table)
		return i2c_match_id(driver->id_table, client) != NULL;

	return 0;
}

static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	struct i2c_client *client = to_i2c_client(dev);
	int rc;

	rc = acpi_device_uevent_modalias(dev, env);
	if (rc != -ENODEV)
		return rc;

	return add_uevent_var(env, "MODALIAS=%s%s", I2C_MODULE_PREFIX, client->name);
}

/* i2c bus recovery routines */
static int get_scl_gpio_value(struct i2c_adapter *adap)
{
	return gpio_get_value(adap->bus_recovery_info->scl_gpio);
}

static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
{
	gpio_set_value(adap->bus_recovery_info->scl_gpio, val);
}

static int get_sda_gpio_value(struct i2c_adapter *adap)
{
	return gpio_get_value(adap->bus_recovery_info->sda_gpio);
}

static int i2c_get_gpios_for_recovery(struct i2c_adapter *adap)
{
	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
	struct device *dev = &adap->dev;
	int ret = 0;

	ret = gpio_request_one(bri->scl_gpio, GPIOF_OPEN_DRAIN |
			GPIOF_OUT_INIT_HIGH, "i2c-scl");
	if (ret) {
		dev_warn(dev, "Can't get SCL gpio: %d\n", bri->scl_gpio);
		return ret;
	}

	if (bri->get_sda) {
		if (gpio_request_one(bri->sda_gpio, GPIOF_IN, "i2c-sda")) {
			/* work without SDA polling */
			dev_warn(dev, "Can't get SDA gpio: %d. Not using SDA polling\n",
					bri->sda_gpio);
			bri->get_sda = NULL;
		}
	}

	return ret;
}

static void i2c_put_gpios_for_recovery(struct i2c_adapter *adap)
{
	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;

	if (bri->get_sda)
		gpio_free(bri->sda_gpio);

	gpio_free(bri->scl_gpio);
}

/*
 * We are generating clock pulses. ndelay() determines durating of clk pulses.
 * We will generate clock with rate 100 KHz and so duration of both clock levels
 * is: delay in ns = (10^6 / 100) / 2
 */
#define RECOVERY_NDELAY		5000
#define RECOVERY_CLK_CNT	9

static int i2c_generic_recovery(struct i2c_adapter *adap)
{
	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
	int i = 0, val = 1, ret = 0;

	if (bri->prepare_recovery)
		bri->prepare_recovery(adap);

	bri->set_scl(adap, val);
	ndelay(RECOVERY_NDELAY);

	/*
	 * By this time SCL is high, as we need to give 9 falling-rising edges
	 */
	while (i++ < RECOVERY_CLK_CNT * 2) {
		if (val) {
			/* Break if SDA is high */
			if (bri->get_sda && bri->get_sda(adap))
					break;
			/* SCL shouldn't be low here */
			if (!bri->get_scl(adap)) {
				dev_err(&adap->dev,
					"SCL is stuck low, exit recovery\n");
				ret = -EBUSY;
				break;
			}
		}

		val = !val;
		bri->set_scl(adap, val);
		ndelay(RECOVERY_NDELAY);
	}

	if (bri->unprepare_recovery)
		bri->unprepare_recovery(adap);

	return ret;
}

int i2c_generic_scl_recovery(struct i2c_adapter *adap)
{
	return i2c_generic_recovery(adap);
}
EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);

int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
{
	int ret;

	ret = i2c_get_gpios_for_recovery(adap);
	if (ret)
		return ret;

	ret = i2c_generic_recovery(adap);
	i2c_put_gpios_for_recovery(adap);

	return ret;
}
EXPORT_SYMBOL_GPL(i2c_generic_gpio_recovery);

int i2c_recover_bus(struct i2c_adapter *adap)
{
	if (!adap->bus_recovery_info)
		return -EOPNOTSUPP;

	dev_dbg(&adap->dev, "Trying i2c bus recovery\n");
	return adap->bus_recovery_info->recover_bus(adap);
}
EXPORT_SYMBOL_GPL(i2c_recover_bus);

static void i2c_init_recovery(struct i2c_adapter *adap)
{
	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
	char *err_str;

	if (!bri)
		return;

	if (!bri->recover_bus) {
		err_str = "no recover_bus() found";
		goto err;
	}

	/* Generic GPIO recovery */
	if (bri->recover_bus == i2c_generic_gpio_recovery) {
		if (!gpio_is_valid(bri->scl_gpio)) {
			err_str = "invalid SCL gpio";
			goto err;
		}

		if (gpio_is_valid(bri->sda_gpio))
			bri->get_sda = get_sda_gpio_value;
		else
			bri->get_sda = NULL;

		bri->get_scl = get_scl_gpio_value;
		bri->set_scl = set_scl_gpio_value;
	} else if (bri->recover_bus == i2c_generic_scl_recovery) {
		/* Generic SCL recovery */
		if (!bri->set_scl || !bri->get_scl) {
			err_str = "no {get|set}_scl() found";
			goto err;
		}
	}

	return;
 err:
	dev_err(&adap->dev, "Not using recovery: %s\n", err_str);
	adap->bus_recovery_info = NULL;
}

static int i2c_device_probe(struct device *dev)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;
	int status;

	if (!client)
		return 0;

	if (!client->irq) {
		int irq = -ENOENT;

		if (dev->of_node) {
			irq = of_irq_get_byname(dev->of_node, "irq");
			if (irq == -EINVAL || irq == -ENODATA)
				irq = of_irq_get(dev->of_node, 0);
		} else if (ACPI_COMPANION(dev)) {
			irq = acpi_dev_gpio_irq_get(ACPI_COMPANION(dev), 0);
		}
		if (irq == -EPROBE_DEFER)
			return irq;
		if (irq < 0)
			irq = 0;

		client->irq = irq;
	}

	driver = to_i2c_driver(dev->driver);
	if (!driver->probe || !driver->id_table)
		return -ENODEV;

	if (client->flags & I2C_CLIENT_WAKE) {
		int wakeirq = -ENOENT;

		if (dev->of_node) {
			wakeirq = of_irq_get_byname(dev->of_node, "wakeup");
			if (wakeirq == -EPROBE_DEFER)
				return wakeirq;
		}

		device_init_wakeup(&client->dev, true);

		if (wakeirq > 0 && wakeirq != client->irq)
			status = dev_pm_set_dedicated_wake_irq(dev, wakeirq);
		else if (client->irq > 0)
			status = dev_pm_set_wake_irq(dev, client->irq);
		else
			status = 0;

		if (status)
			dev_warn(&client->dev, "failed to set up wakeup irq");
	}

	dev_dbg(dev, "probe\n");

	status = of_clk_set_defaults(dev->of_node, false);
	if (status < 0)
		goto err_clear_wakeup_irq;

	status = dev_pm_domain_attach(&client->dev, true);
	if (status == -EPROBE_DEFER)
		goto err_clear_wakeup_irq;

	status = driver->probe(client, i2c_match_id(driver->id_table, client));
	if (status)
		goto err_detach_pm_domain;

	return 0;

err_detach_pm_domain:
	dev_pm_domain_detach(&client->dev, true);
err_clear_wakeup_irq:
	dev_pm_clear_wake_irq(&client->dev);
	device_init_wakeup(&client->dev, false);
	return status;
}

static int i2c_device_remove(struct device *dev)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;
	int status = 0;

	if (!client || !dev->driver)
		return 0;

	driver = to_i2c_driver(dev->driver);
	if (driver->remove) {
		dev_dbg(dev, "remove\n");
		status = driver->remove(client);
	}

	dev_pm_domain_detach(&client->dev, true);

	dev_pm_clear_wake_irq(&client->dev);
	device_init_wakeup(&client->dev, false);

	return status;
}

static void i2c_device_shutdown(struct device *dev)
{
	struct i2c_client *client = i2c_verify_client(dev);
	struct i2c_driver *driver;

	if (!client || !dev->driver)
		return;
	driver = to_i2c_driver(dev->driver);
	if (driver->shutdown)
		driver->shutdown(client);
}

static void i2c_client_dev_release(struct device *dev)
{
	kfree(to_i2c_client(dev));
}

static ssize_t
show_name(struct device *dev, struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%s\n", dev->type == &i2c_client_type ?
		       to_i2c_client(dev)->name : to_i2c_adapter(dev)->name);
}
static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);

static ssize_t
show_modalias(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	int len;

	len = acpi_device_modalias(dev, buf, PAGE_SIZE -1);
	if (len != -ENODEV)
		return len;

	return sprintf(buf, "%s%s\n", I2C_MODULE_PREFIX, client->name);
}
static DEVICE_ATTR(modalias, S_IRUGO, show_modalias, NULL);

static struct attribute *i2c_dev_attrs[] = {
	&dev_attr_name.attr,
	/* modalias helps coldplug:  modprobe $(cat .../modalias) */
	&dev_attr_modalias.attr,
	NULL
};
ATTRIBUTE_GROUPS(i2c_dev);

struct bus_type i2c_bus_type = {
	.name		= "i2c",
	.match		= i2c_device_match,
	.probe		= i2c_device_probe,
	.remove		= i2c_device_remove,
	.shutdown	= i2c_device_shutdown,
};
EXPORT_SYMBOL_GPL(i2c_bus_type);

static struct device_type i2c_client_type = {
	.groups		= i2c_dev_groups,
	.uevent		= i2c_device_uevent,
	.release	= i2c_client_dev_release,
};


/**
 * i2c_verify_client - return parameter as i2c_client, or NULL
 * @dev: device, probably from some driver model iterator
 *
 * When traversing the driver model tree, perhaps using driver model
 * iterators like @device_for_each_child(), you can't assume very much
 * about the nodes you find.  Use this function to avoid oopses caused
 * by wrongly treating some non-I2C device as an i2c_client.
 */
struct i2c_client *i2c_verify_client(struct device *dev)
{
	return (dev->type == &i2c_client_type)
			? to_i2c_client(dev)
			: NULL;
}
EXPORT_SYMBOL(i2c_verify_client);


/* Return a unique address which takes the flags of the client into account */
static unsigned short i2c_encode_flags_to_addr(struct i2c_client *client)
{
	unsigned short addr = client->addr;

	/* For some client flags, add an arbitrary offset to avoid collisions */
	if (client->flags & I2C_CLIENT_TEN)
		addr |= I2C_ADDR_OFFSET_TEN_BIT;

	if (client->flags & I2C_CLIENT_SLAVE)
		addr |= I2C_ADDR_OFFSET_SLAVE;

	return addr;
}

/* This is a permissive address validity check, I2C address map constraints
 * are purposely not enforced, except for the general call address. */
static int i2c_check_addr_validity(unsigned addr, unsigned short flags)
{
	if (flags & I2C_CLIENT_TEN) {
		/* 10-bit address, all values are valid */
		if (addr > 0x3ff)
			return -EINVAL;
	} else {
		/* 7-bit address, reject the general call address */
		if (addr == 0x00 || addr > 0x7f)
			return -EINVAL;
	}
	return 0;
}

/* And this is a strict address validity check, used when probing. If a
 * device uses a reserved address, then it shouldn't be probed. 7-bit
 * addressing is assumed, 10-bit address devices are rare and should be
 * explicitly enumerated. */
static int i2c_check_7bit_addr_validity_strict(unsigned short addr)
{
	/*
	 * Reserved addresses per I2C specification:
	 *  0x00       General call address / START byte
	 *  0x01       CBUS address
	 *  0x02       Reserved for different bus format
	 *  0x03       Reserved for future purposes
	 *  0x04-0x07  Hs-mode master code
	 *  0x78-0x7b  10-bit slave addressing
	 *  0x7c-0x7f  Reserved for future purposes
	 */
	if (addr < 0x08 || addr > 0x77)
		return -EINVAL;
	return 0;
}

static int __i2c_check_addr_busy(struct device *dev, void *addrp)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	int			addr = *(int *)addrp;

	if (client && i2c_encode_flags_to_addr(client) == addr)
		return -EBUSY;
	return 0;
}

/* walk up mux tree */
static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result;

	result = device_for_each_child(&adapter->dev, &addr,
					__i2c_check_addr_busy);

	if (!result && parent)
		result = i2c_check_mux_parents(parent, addr);

	return result;
}

/* recurse down mux tree */
static int i2c_check_mux_children(struct device *dev, void *addrp)
{
	int result;

	if (dev->type == &i2c_adapter_type)
		result = device_for_each_child(dev, addrp,
						i2c_check_mux_children);
	else
		result = __i2c_check_addr_busy(dev, addrp);

	return result;
}

static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result = 0;

	if (parent)
		result = i2c_check_mux_parents(parent, addr);

	if (!result)
		result = device_for_each_child(&adapter->dev, &addr,
						i2c_check_mux_children);

	return result;
}

/**
 * i2c_adapter_lock_bus - Get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER locks the root i2c adapter, I2C_LOCK_SEGMENT
 *	locks only this branch in the adapter tree
 */
static void i2c_adapter_lock_bus(struct i2c_adapter *adapter,
				 unsigned int flags)
{
	rt_mutex_lock(&adapter->bus_lock);
}

/**
 * i2c_adapter_trylock_bus - Try to get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER trylocks the root i2c adapter, I2C_LOCK_SEGMENT
 *	trylocks only this branch in the adapter tree
 */
static int i2c_adapter_trylock_bus(struct i2c_adapter *adapter,
				   unsigned int flags)
{
	return rt_mutex_trylock(&adapter->bus_lock);
}

/**
 * i2c_adapter_unlock_bus - Release exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER unlocks the root i2c adapter, I2C_LOCK_SEGMENT
 *	unlocks only this branch in the adapter tree
 */
static void i2c_adapter_unlock_bus(struct i2c_adapter *adapter,
				   unsigned int flags)
{
	rt_mutex_unlock(&adapter->bus_lock);
}

static void i2c_dev_set_name(struct i2c_adapter *adap,
			     struct i2c_client *client)
{
	struct acpi_device *adev = ACPI_COMPANION(&client->dev);

	if (adev) {
		dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
		return;
	}

	dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
		     i2c_encode_flags_to_addr(client));
}

/**
 * i2c_new_device - instantiate an i2c device
 * @adap: the adapter managing the device
 * @info: describes one I2C device; bus_num is ignored
 * Context: can sleep
 *
 * Create an i2c device. Binding is handled through driver model
 * probe()/remove() methods.  A driver may be bound to this device when we
 * return from this function, or any later moment (e.g. maybe hotplugging will
 * load the driver module).  This call is not appropriate for use by mainboard
 * initialization logic, which usually runs during an arch_initcall() long
 * before any i2c_adapter could exist.
 *
 * This returns the new i2c client, which may be saved for later use with
 * i2c_unregister_device(); or NULL to indicate an error.
 */
struct i2c_client *
i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
	struct i2c_client	*client;
	int			status;

	client = kzalloc(sizeof *client, GFP_KERNEL);
	if (!client)
		return NULL;

	client->adapter = adap;

	client->dev.platform_data = info->platform_data;

	if (info->archdata)
		client->dev.archdata = *info->archdata;

	client->flags = info->flags;
	client->addr = info->addr;
	client->irq = info->irq;

	strlcpy(client->name, info->type, sizeof(client->name));

	status = i2c_check_addr_validity(client->addr, client->flags);
	if (status) {
		dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx\n",
			client->flags & I2C_CLIENT_TEN ? 10 : 7, client->addr);
		goto out_err_silent;
	}

	/* Check for address business */
	status = i2c_check_addr_busy(adap, i2c_encode_flags_to_addr(client));
	if (status)
		goto out_err;

	client->dev.parent = &client->adapter->dev;
	client->dev.bus = &i2c_bus_type;
	client->dev.type = &i2c_client_type;
	client->dev.of_node = info->of_node;
	client->dev.fwnode = info->fwnode;

	i2c_dev_set_name(adap, client);
	status = device_register(&client->dev);
	if (status)
		goto out_err;

	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
		client->name, dev_name(&client->dev));

	return client;

out_err:
	dev_err(&adap->dev, "Failed to register i2c client %s at 0x%02x "
		"(%d)\n", client->name, client->addr, status);
out_err_silent:
	kfree(client);
	return NULL;
}
EXPORT_SYMBOL_GPL(i2c_new_device);


/**
 * i2c_unregister_device - reverse effect of i2c_new_device()
 * @client: value returned from i2c_new_device()
 * Context: can sleep
 */
void i2c_unregister_device(struct i2c_client *client)
{
	if (client->dev.of_node)
		of_node_clear_flag(client->dev.of_node, OF_POPULATED);
	if (ACPI_COMPANION(&client->dev))
		acpi_device_clear_enumerated(ACPI_COMPANION(&client->dev));
	device_unregister(&client->dev);
}
EXPORT_SYMBOL_GPL(i2c_unregister_device);


static const struct i2c_device_id dummy_id[] = {
	{ "dummy", 0 },
	{ },
};

static int dummy_probe(struct i2c_client *client,
		       const struct i2c_device_id *id)
{
	return 0;
}

static int dummy_remove(struct i2c_client *client)
{
	return 0;
}

static struct i2c_driver dummy_driver = {
	.driver.name	= "dummy",
	.probe		= dummy_probe,
	.remove		= dummy_remove,
	.id_table	= dummy_id,
};

/**
 * i2c_new_dummy - return a new i2c device bound to a dummy driver
 * @adapter: the adapter managing the device
 * @address: seven bit address to be used
 * Context: can sleep
 *
 * This returns an I2C client bound to the "dummy" driver, intended for use
 * with devices that consume multiple addresses.  Examples of such chips
 * include various EEPROMS (like 24c04 and 24c08 models).
 *
 * These dummy devices have two main uses.  First, most I2C and SMBus calls
 * except i2c_transfer() need a client handle; the dummy will be that handle.
 * And second, this prevents the specified address from being bound to a
 * different driver.
 *
 * This returns the new i2c client, which should be saved for later use with
 * i2c_unregister_device(); or NULL to indicate an error.
 */
struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
{
	struct i2c_board_info info = {
		I2C_BOARD_INFO("dummy", address),
	};

	return i2c_new_device(adapter, &info);
}
EXPORT_SYMBOL_GPL(i2c_new_dummy);

/**
 * i2c_new_secondary_device - Helper to get the instantiated secondary address
 * and create the associated device
 * @client: Handle to the primary client
 * @name: Handle to specify which secondary address to get
 * @default_addr: Used as a fallback if no secondary address was specified
 * Context: can sleep
 *
 * I2C clients can be composed of multiple I2C slaves bound together in a single
 * component. The I2C client driver then binds to the master I2C slave and needs
 * to create I2C dummy clients to communicate with all the other slaves.
 *
 * This function creates and returns an I2C dummy client whose I2C address is
 * retrieved from the platform firmware based on the given slave name. If no
 * address is specified by the firmware default_addr is used.
 *
 * On DT-based platforms the address is retrieved from the "reg" property entry
 * cell whose "reg-names" value matches the slave name.
 *
 * This returns the new i2c client, which should be saved for later use with
 * i2c_unregister_device(); or NULL to indicate an error.
 */
struct i2c_client *i2c_new_secondary_device(struct i2c_client *client,
						const char *name,
						u16 default_addr)
{
	struct device_node *np = client->dev.of_node;
	u32 addr = default_addr;
	int i;

	if (np) {
		i = of_property_match_string(np, "reg-names", name);
		if (i >= 0)
			of_property_read_u32_index(np, "reg", i, &addr);
	}

	dev_dbg(&client->adapter->dev, "Address for %s : 0x%x\n", name, addr);
	return i2c_new_dummy(client->adapter, addr);
}
EXPORT_SYMBOL_GPL(i2c_new_secondary_device);

/* ------------------------------------------------------------------------- */

/* I2C bus adapters -- one roots each I2C or SMBUS segment */

static void i2c_adapter_dev_release(struct device *dev)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	complete(&adap->dev_released);
}

/*
 * This function is only needed for mutex_lock_nested, so it is never
 * called unless locking correctness checking is enabled. Thus we
 * make it inline to avoid a compiler warning. That's what gcc ends up
 * doing anyway.
 */
static inline unsigned int i2c_adapter_depth(struct i2c_adapter *adapter)
{
	unsigned int depth = 0;

	while ((adapter = i2c_parent_is_i2c_adapter(adapter)))
		depth++;

	return depth;
}

/*
 * Let users instantiate I2C devices through sysfs. This can be used when
 * platform initialization code doesn't contain the proper data for
 * whatever reason. Also useful for drivers that do device detection and
 * detection fails, either because the device uses an unexpected address,
 * or this is a compatible device with different ID register values.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to provide incorrect parameters.
 */
static ssize_t
i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
		     const char *buf, size_t count)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	struct i2c_board_info info;
	struct i2c_client *client;
	char *blank, end;
	int res;

	memset(&info, 0, sizeof(struct i2c_board_info));

	blank = strchr(buf, ' ');
	if (!blank) {
		dev_err(dev, "%s: Missing parameters\n", "new_device");
		return -EINVAL;
	}
	if (blank - buf > I2C_NAME_SIZE - 1) {
		dev_err(dev, "%s: Invalid device name\n", "new_device");
		return -EINVAL;
	}
	memcpy(info.type, buf, blank - buf);

	/* Parse remaining parameters, reject extra parameters */
	res = sscanf(++blank, "%hi%c", &info.addr, &end);
	if (res < 1) {
		dev_err(dev, "%s: Can't parse I2C address\n", "new_device");
		return -EINVAL;
	}
	if (res > 1  && end != '\n') {
		dev_err(dev, "%s: Extra parameters\n", "new_device");
		return -EINVAL;
	}

	if ((info.addr & I2C_ADDR_OFFSET_TEN_BIT) == I2C_ADDR_OFFSET_TEN_BIT) {
		info.addr &= ~I2C_ADDR_OFFSET_TEN_BIT;
		info.flags |= I2C_CLIENT_TEN;
	}

	if (info.addr & I2C_ADDR_OFFSET_SLAVE) {
		info.addr &= ~I2C_ADDR_OFFSET_SLAVE;
		info.flags |= I2C_CLIENT_SLAVE;
	}

	client = i2c_new_device(adap, &info);
	if (!client)
		return -EINVAL;

	/* Keep track of the added device */
	mutex_lock(&adap->userspace_clients_lock);
	list_add_tail(&client->detected, &adap->userspace_clients);
	mutex_unlock(&adap->userspace_clients_lock);
	dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
		 info.type, info.addr);

	return count;
}
static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device);

/*
 * And of course let the users delete the devices they instantiated, if
 * they got it wrong. This interface can only be used to delete devices
 * instantiated by i2c_sysfs_new_device above. This guarantees that we
 * don't delete devices to which some kernel code still has references.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to delete the wrong device.
 */
static ssize_t
i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
			const char *buf, size_t count)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	struct i2c_client *client, *next;
	unsigned short addr;
	char end;
	int res;

	/* Parse parameters, reject extra parameters */
	res = sscanf(buf, "%hi%c", &addr, &end);
	if (res < 1) {
		dev_err(dev, "%s: Can't parse I2C address\n", "delete_device");
		return -EINVAL;
	}
	if (res > 1  && end != '\n') {
		dev_err(dev, "%s: Extra parameters\n", "delete_device");
		return -EINVAL;
	}

	/* Make sure the device was added through sysfs */
	res = -ENOENT;
	mutex_lock_nested(&adap->userspace_clients_lock,
			  i2c_adapter_depth(adap));
	list_for_each_entry_safe(client, next, &adap->userspace_clients,
				 detected) {
		if (i2c_encode_flags_to_addr(client) == addr) {
			dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",
				 "delete_device", client->name, client->addr);

			list_del(&client->detected);
			i2c_unregister_device(client);
			res = count;
			break;
		}
	}
	mutex_unlock(&adap->userspace_clients_lock);

	if (res < 0)
		dev_err(dev, "%s: Can't find device in list\n",
			"delete_device");
	return res;
}
static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL,
				   i2c_sysfs_delete_device);

static struct attribute *i2c_adapter_attrs[] = {
	&dev_attr_name.attr,
	&dev_attr_new_device.attr,
	&dev_attr_delete_device.attr,
	NULL
};
ATTRIBUTE_GROUPS(i2c_adapter);

struct device_type i2c_adapter_type = {
	.groups		= i2c_adapter_groups,
	.release	= i2c_adapter_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_adapter_type);

/**
 * i2c_verify_adapter - return parameter as i2c_adapter or NULL
 * @dev: device, probably from some driver model iterator
 *
 * When traversing the driver model tree, perhaps using driver model
 * iterators like @device_for_each_child(), you can't assume very much
 * about the nodes you find.  Use this function to avoid oopses caused
 * by wrongly treating some non-I2C device as an i2c_adapter.
 */
struct i2c_adapter *i2c_verify_adapter(struct device *dev)
{
	return (dev->type == &i2c_adapter_type)
			? to_i2c_adapter(dev)
			: NULL;
}
EXPORT_SYMBOL(i2c_verify_adapter);

#ifdef CONFIG_I2C_COMPAT
static struct class_compat *i2c_adapter_compat_class;
#endif

static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
{
	struct i2c_devinfo	*devinfo;

	down_read(&__i2c_board_lock);
	list_for_each_entry(devinfo, &__i2c_board_list, list) {
		if (devinfo->busnum == adapter->nr
				&& !i2c_new_device(adapter,
						&devinfo->board_info))
			dev_err(&adapter->dev,
				"Can't create device at 0x%02x\n",
				devinfo->board_info.addr);
	}
	up_read(&__i2c_board_lock);
}

/* OF support code */

#if IS_ENABLED(CONFIG_OF)
static struct i2c_client *of_i2c_register_device(struct i2c_adapter *adap,
						 struct device_node *node)
{
	struct i2c_client *result;
	struct i2c_board_info info = {};
	struct dev_archdata dev_ad = {};
	const __be32 *addr_be;
	u32 addr;
	int len;

	dev_dbg(&adap->dev, "of_i2c: register %s\n", node->full_name);

	if (of_modalias_node(node, info.type, sizeof(info.type)) < 0) {
		dev_err(&adap->dev, "of_i2c: modalias failure on %s\n",
			node->full_name);
		return ERR_PTR(-EINVAL);
	}

	addr_be = of_get_property(node, "reg", &len);
	if (!addr_be || (len < sizeof(*addr_be))) {
		dev_err(&adap->dev, "of_i2c: invalid reg on %s\n",
			node->full_name);
		return ERR_PTR(-EINVAL);
	}

	addr = be32_to_cpup(addr_be);
	if (addr & I2C_TEN_BIT_ADDRESS) {
		addr &= ~I2C_TEN_BIT_ADDRESS;
		info.flags |= I2C_CLIENT_TEN;
	}

	if (addr & I2C_OWN_SLAVE_ADDRESS) {
		addr &= ~I2C_OWN_SLAVE_ADDRESS;
		info.flags |= I2C_CLIENT_SLAVE;
	}

	if (i2c_check_addr_validity(addr, info.flags)) {
		dev_err(&adap->dev, "of_i2c: invalid addr=%x on %s\n",
			info.addr, node->full_name);
		return ERR_PTR(-EINVAL);
	}

	info.addr = addr;
	info.of_node = of_node_get(node);
	info.archdata = &dev_ad;

	if (of_get_property(node, "wakeup-source", NULL))
		info.flags |= I2C_CLIENT_WAKE;

	result = i2c_new_device(adap, &info);
	if (result == NULL) {
		dev_err(&adap->dev, "of_i2c: Failure registering %s\n",
			node->full_name);
		of_node_put(node);
		return ERR_PTR(-EINVAL);
	}
	return result;
}

static void of_i2c_register_devices(struct i2c_adapter *adap)
{
	struct device_node *node;

	/* Only register child devices if the adapter has a node pointer set */
	if (!adap->dev.of_node)
		return;

	dev_dbg(&adap->dev, "of_i2c: walking child nodes\n");

	for_each_available_child_of_node(adap->dev.of_node, node) {
		if (of_node_test_and_set_flag(node, OF_POPULATED))
			continue;
		of_i2c_register_device(adap, node);
	}
}

static int of_dev_node_match(struct device *dev, void *data)
{
	return dev->of_node == data;
}

/* must call put_device() when done with returned i2c_client device */
struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
{
	struct device *dev;
	struct i2c_client *client;

	dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match);
	if (!dev)
		return NULL;

	client = i2c_verify_client(dev);
	if (!client)
		put_device(dev);

	return client;
}
EXPORT_SYMBOL(of_find_i2c_device_by_node);

/* must call put_device() when done with returned i2c_adapter device */
struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
{
	struct device *dev;
	struct i2c_adapter *adapter;

	dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match);
	if (!dev)
		return NULL;

	adapter = i2c_verify_adapter(dev);
	if (!adapter)
		put_device(dev);

	return adapter;
}
EXPORT_SYMBOL(of_find_i2c_adapter_by_node);

/* must call i2c_put_adapter() when done with returned i2c_adapter device */
struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node)
{
	struct i2c_adapter *adapter;

	adapter = of_find_i2c_adapter_by_node(node);
	if (!adapter)
		return NULL;

	if (!try_module_get(adapter->owner)) {
		put_device(&adapter->dev);
		adapter = NULL;
	}

	return adapter;
}
EXPORT_SYMBOL(of_get_i2c_adapter_by_node);
#else
static void of_i2c_register_devices(struct i2c_adapter *adap) { }
#endif /* CONFIG_OF */

static int i2c_do_add_adapter(struct i2c_driver *driver,
			      struct i2c_adapter *adap)
{
	/* Detect supported devices on that bus, and instantiate them */
	i2c_detect(adap, driver);

	/* Let legacy drivers scan this bus for matching devices */
	if (driver->attach_adapter) {
		dev_warn(&adap->dev, "%s: attach_adapter method is deprecated\n",
			 driver->driver.name);
		dev_warn(&adap->dev, "Please use another way to instantiate "
			 "your i2c_client\n");
		/* We ignore the return code; if it fails, too bad */
		driver->attach_adapter(adap);
	}
	return 0;
}

static int __process_new_adapter(struct device_driver *d, void *data)
{
	return i2c_do_add_adapter(to_i2c_driver(d), data);
}

static int i2c_register_adapter(struct i2c_adapter *adap)
{
	int res = -EINVAL;

	/* Can't register until after driver model init */
	if (WARN_ON(!is_registered)) {
		res = -EAGAIN;
		goto out_list;
	}

	/* Sanity checks */
	if (WARN(!adap->name[0], "i2c adapter has no name"))
		goto out_list;

	if (!adap->algo) {
		pr_err("adapter '%s': no algo supplied!\n", adap->name);
		goto out_list;
	}

	if (!adap->lock_bus) {
		adap->lock_bus = i2c_adapter_lock_bus;
		adap->trylock_bus = i2c_adapter_trylock_bus;
		adap->unlock_bus = i2c_adapter_unlock_bus;
	}

	rt_mutex_init(&adap->bus_lock);
	rt_mutex_init(&adap->mux_lock);
	mutex_init(&adap->userspace_clients_lock);
	INIT_LIST_HEAD(&adap->userspace_clients);

	/* Set default timeout to 1 second if not already set */
	if (adap->timeout == 0)
		adap->timeout = HZ;

	dev_set_name(&adap->dev, "i2c-%d", adap->nr);
	adap->dev.bus = &i2c_bus_type;
	adap->dev.type = &i2c_adapter_type;
	res = device_register(&adap->dev);
	if (res) {
		pr_err("adapter '%s': can't register device (%d)\n", adap->name, res);
		goto out_list;
	}

	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);

	pm_runtime_no_callbacks(&adap->dev);
	pm_suspend_ignore_children(&adap->dev, true);
	pm_runtime_enable(&adap->dev);

#ifdef CONFIG_I2C_COMPAT
	res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,
				       adap->dev.parent);
	if (res)
		dev_warn(&adap->dev,
			 "Failed to create compatibility class link\n");
#endif

	i2c_init_recovery(adap);

	/* create pre-declared device nodes */
	of_i2c_register_devices(adap);
	acpi_i2c_register_devices(adap);
	acpi_i2c_install_space_handler(adap);

	if (adap->nr < __i2c_first_dynamic_bus_num)
		i2c_scan_static_board_info(adap);

	/* Notify drivers */
	mutex_lock(&core_lock);
	bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
	mutex_unlock(&core_lock);

	return 0;

out_list:
	mutex_lock(&core_lock);
	idr_remove(&i2c_adapter_idr, adap->nr);
	mutex_unlock(&core_lock);
	return res;
}

/**
 * __i2c_add_numbered_adapter - i2c_add_numbered_adapter where nr is never -1
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * See i2c_add_numbered_adapter() for details.
 */
static int __i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
	int id;

	mutex_lock(&core_lock);
	id = idr_alloc(&i2c_adapter_idr, adap, adap->nr, adap->nr + 1, GFP_KERNEL);
	mutex_unlock(&core_lock);
	if (WARN(id < 0, "couldn't get idr"))
		return id == -ENOSPC ? -EBUSY : id;

	return i2c_register_adapter(adap);
}

/**
 * i2c_add_adapter - declare i2c adapter, use dynamic bus number
 * @adapter: the adapter to add
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * doesn't matter or when its bus number is specified by an dt alias.
 * Examples of bases when the bus number doesn't matter: I2C adapters
 * dynamically added by USB links or PCI plugin cards.
 *
 * When this returns zero, a new bus number was allocated and stored
 * in adap->nr, and the specified adapter became available for clients.
 * Otherwise, a negative errno value is returned.
 */
int i2c_add_adapter(struct i2c_adapter *adapter)
{
	struct device *dev = &adapter->dev;
	int id;

	if (dev->of_node) {
		id = of_alias_get_id(dev->of_node, "i2c");
		if (id >= 0) {
			adapter->nr = id;
			return __i2c_add_numbered_adapter(adapter);
		}
	}

	mutex_lock(&core_lock);
	id = idr_alloc(&i2c_adapter_idr, adapter,
		       __i2c_first_dynamic_bus_num, 0, GFP_KERNEL);
	mutex_unlock(&core_lock);
	if (WARN(id < 0, "couldn't get idr"))
		return id;

	adapter->nr = id;

	return i2c_register_adapter(adapter);
}
EXPORT_SYMBOL(i2c_add_adapter);

/**
 * i2c_add_numbered_adapter - declare i2c adapter, use static bus number
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * matters.  For example, use it for I2C adapters from system-on-chip CPUs,
 * or otherwise built in to the system's mainboard, and where i2c_board_info
 * is used to properly configure I2C devices.
 *
 * If the requested bus number is set to -1, then this function will behave
 * identically to i2c_add_adapter, and will dynamically assign a bus number.
 *
 * If no devices have pre-been declared for this bus, then be sure to
 * register the adapter before any dynamically allocated ones.  Otherwise
 * the required bus ID may not be available.
 *
 * When this returns zero, the specified adapter became available for
 * clients using the bus number provided in adap->nr.  Also, the table
 * of I2C devices pre-declared using i2c_register_board_info() is scanned,
 * and the appropriate driver model device nodes are created.  Otherwise, a
 * negative errno value is returned.
 */
int i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
	if (adap->nr == -1) /* -1 means dynamically assign bus id */
		return i2c_add_adapter(adap);

	return __i2c_add_numbered_adapter(adap);
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);

static void i2c_do_del_adapter(struct i2c_driver *driver,
			      struct i2c_adapter *adapter)
{
	struct i2c_client *client, *_n;

	/* Remove the devices we created ourselves as the result of hardware
	 * probing (using a driver's detect method) */
	list_for_each_entry_safe(client, _n, &driver->clients, detected) {
		if (client->adapter == adapter) {
			dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
				client->name, client->addr);
			list_del(&client->detected);
			i2c_unregister_device(client);
		}
	}
}

static int __unregister_client(struct device *dev, void *dummy)
{
	struct i2c_client *client = i2c_verify_client(dev);
	if (client && strcmp(client->name, "dummy"))
		i2c_unregister_device(client);
	return 0;
}

static int __unregister_dummy(struct device *dev, void *dummy)
{
	struct i2c_client *client = i2c_verify_client(dev);
	if (client)
		i2c_unregister_device(client);
	return 0;
}

static int __process_removed_adapter(struct device_driver *d, void *data)
{
	i2c_do_del_adapter(to_i2c_driver(d), data);
	return 0;
}

/**
 * i2c_del_adapter - unregister I2C adapter
 * @adap: the adapter being unregis…