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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Linux I2C core
  *
  * Copyright (C) 1995-99 Simon G. Vogl
  *   With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>
  *   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
  *   Michael Lawnick <michael.lawnick.ext@nsn.com>
  *
  * Copyright (C) 2013-2017 Wolfram Sang <wsa@kernel.org>
  */
 
 #define pr_fmt(fmt) "i2c-core: " fmt
 
 #include <dt-bindings/i2c/i2c.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/consumer.h>
 #include <linux/i2c.h>
 #include <linux/i2c-smbus.h>
 #include <linux/idr.h>
 #include <linux/init.h>
 #include <linux/interrupt.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/pinctrl/consumer.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
 
 #define I2C_ADDR_7BITS_MAX  0x77
 #define I2C_ADDR_7BITS_COUNT    (I2C_ADDR_7BITS_MAX + 1)
 
 #define I2C_ADDR_DEVICE_ID  0x7c
 
 /*
  * core_lock protects i2c_adapter_idr, and guarantees that device detection,
  * deletion of detected devices are serialized
  */
 static DEFINE_MUTEX(core_lock);
 static DEFINE_IDR(i2c_adapter_idr);
 
 static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);
 
 static DEFINE_STATIC_KEY_FALSE(i2c_trace_msg_key);
 static bool is_registered;
 
 int i2c_transfer_trace_reg(void)
 {
     static_branch_inc(&i2c_trace_msg_key);
     return 0;
 }
 
 void i2c_transfer_trace_unreg(void)
 {
     static_branch_dec(&i2c_trace_msg_key);
 }
 
 const char *i2c_freq_mode_string(u32 bus_freq_hz)
 {
     switch (bus_freq_hz) {
     case I2C_MAX_STANDARD_MODE_FREQ:
         return "Standard Mode (100 kHz)";
     case I2C_MAX_FAST_MODE_FREQ:
         return "Fast Mode (400 kHz)";
     case I2C_MAX_FAST_MODE_PLUS_FREQ:
         return "Fast Mode Plus (1.0 MHz)";
     case I2C_MAX_TURBO_MODE_FREQ:
         return "Turbo Mode (1.4 MHz)";
     case I2C_MAX_HIGH_SPEED_MODE_FREQ:
         return "High Speed Mode (3.4 MHz)";
     case I2C_MAX_ULTRA_FAST_MODE_FREQ:
         return "Ultra Fast Mode (5.0 MHz)";
     default:
         return "Unknown Mode";
     }
 }
 EXPORT_SYMBOL_GPL(i2c_freq_mode_string);
 
 const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
                         const struct i2c_client *client)
 {
     if (!(id && client))
         return NULL;
 
     while (id->name[0]) {
         if (strcmp(client->name, id->name) == 0)
             return id;
         id++;
     }
     return NULL;
 }
 EXPORT_SYMBOL_GPL(i2c_match_id);
 
 static int i2c_device_match(struct device *dev, struct device_driver *drv)
 {
     struct i2c_client   *client = i2c_verify_client(dev);
     struct i2c_driver   *driver;
 
 
     /* Attempt an OF style match */
     if (i2c_of_match_device(drv->of_match_table, client))
         return 1;
 
     /* Then ACPI style match */
     if (acpi_driver_match_device(dev, drv))
         return 1;
 
     driver = to_i2c_driver(drv);
 
     /* Finally an I2C match */
     if (i2c_match_id(driver->id_table, client))
         return 1;
 
     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 = of_device_uevent_modalias(dev, env);
     if (rc != -ENODEV)
         return 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 gpiod_get_value_cansleep(adap->bus_recovery_info->scl_gpiod);
 }
 
 static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
 {
     gpiod_set_value_cansleep(adap->bus_recovery_info->scl_gpiod, val);
 }
 
 static int get_sda_gpio_value(struct i2c_adapter *adap)
 {
     return gpiod_get_value_cansleep(adap->bus_recovery_info->sda_gpiod);
 }
 
 static void set_sda_gpio_value(struct i2c_adapter *adap, int val)
 {
     gpiod_set_value_cansleep(adap->bus_recovery_info->sda_gpiod, val);
 }
 
 static int i2c_generic_bus_free(struct i2c_adapter *adap)
 {
     struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
     int ret = -EOPNOTSUPP;
 
     if (bri->get_bus_free)
         ret = bri->get_bus_free(adap);
     else if (bri->get_sda)
         ret = bri->get_sda(adap);
 
     if (ret < 0)
         return ret;
 
     return ret ? 0 : -EBUSY;
 }
 
 /*
  * 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
 
 int i2c_generic_scl_recovery(struct i2c_adapter *adap)
 {
     struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
     int i = 0, scl = 1, ret = 0;
 
     if (bri->prepare_recovery)
         bri->prepare_recovery(adap);
     if (bri->pinctrl)
         pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
 
     /*
      * If we can set SDA, we will always create a STOP to ensure additional
      * pulses will do no harm. This is achieved by letting SDA follow SCL
      * half a cycle later. Check the 'incomplete_write_byte' fault injector
      * for details. Note that we must honour tsu:sto, 4us, but lets use 5us
      * here for simplicity.
      */
     bri->set_scl(adap, scl);
     ndelay(RECOVERY_NDELAY);
     if (bri->set_sda)
         bri->set_sda(adap, scl);
     ndelay(RECOVERY_NDELAY / 2);
 
     /*
      * By this time SCL is high, as we need to give 9 falling-rising edges
      */
     while (i++ < RECOVERY_CLK_CNT * 2) {
         if (scl) {
             /* 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;
             }
         }
 
         scl = !scl;
         bri->set_scl(adap, scl);
         /* Creating STOP again, see above */
         if (scl)  {
             /* Honour minimum tsu:sto */
             ndelay(RECOVERY_NDELAY);
         } else {
             /* Honour minimum tf and thd:dat */
             ndelay(RECOVERY_NDELAY / 2);
         }
         if (bri->set_sda)
             bri->set_sda(adap, scl);
         ndelay(RECOVERY_NDELAY / 2);
 
         if (scl) {
             ret = i2c_generic_bus_free(adap);
             if (ret == 0)
                 break;
         }
     }
 
     /* If we can't check bus status, assume recovery worked */
     if (ret == -EOPNOTSUPP)
         ret = 0;
 
     if (bri->unprepare_recovery)
         bri->unprepare_recovery(adap);
     if (bri->pinctrl)
         pinctrl_select_state(bri->pinctrl, bri->pins_default);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);
 
 int i2c_recover_bus(struct i2c_adapter *adap)
 {
     if (!adap->bus_recovery_info)
         return -EBUSY;
 
     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_gpio_init_pinctrl_recovery(struct i2c_adapter *adap)
 {
     struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
     struct device *dev = &adap->dev;
     struct pinctrl *p = bri->pinctrl;
 
     /*
      * we can't change states without pinctrl, so remove the states if
      * populated
      */
     if (!p) {
         bri->pins_default = NULL;
         bri->pins_gpio = NULL;
         return;
     }
 
     if (!bri->pins_default) {
         bri->pins_default = pinctrl_lookup_state(p,
                              PINCTRL_STATE_DEFAULT);
         if (IS_ERR(bri->pins_default)) {
             dev_dbg(dev, PINCTRL_STATE_DEFAULT " state not found for GPIO recovery\n");
             bri->pins_default = NULL;
         }
     }
     if (!bri->pins_gpio) {
         bri->pins_gpio = pinctrl_lookup_state(p, "gpio");
         if (IS_ERR(bri->pins_gpio))
             bri->pins_gpio = pinctrl_lookup_state(p, "recovery");
 
         if (IS_ERR(bri->pins_gpio)) {
             dev_dbg(dev, "no gpio or recovery state found for GPIO recovery\n");
             bri->pins_gpio = NULL;
         }
     }
 
     /* for pinctrl state changes, we need all the information */
     if (bri->pins_default && bri->pins_gpio) {
         dev_info(dev, "using pinctrl states for GPIO recovery");
     } else {
         bri->pinctrl = NULL;
         bri->pins_default = NULL;
         bri->pins_gpio = NULL;
     }
 }
 
 static int i2c_gpio_init_generic_recovery(struct i2c_adapter *adap)
 {
     struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
     struct device *dev = &adap->dev;
     struct gpio_desc *gpiod;
     int ret = 0;
 
     /*
      * don't touch the recovery information if the driver is not using
      * generic SCL recovery
      */
     if (bri->recover_bus && bri->recover_bus != i2c_generic_scl_recovery)
         return 0;
 
     /*
      * pins might be taken as GPIO, so we should inform pinctrl about
      * this and move the state to GPIO
      */
     if (bri->pinctrl)
         pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
 
     /*
      * if there is incomplete or no recovery information, see if generic
      * GPIO recovery is available
      */
     if (!bri->scl_gpiod) {
         gpiod = devm_gpiod_get(dev, "scl", GPIOD_OUT_HIGH_OPEN_DRAIN);
         if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
             ret  = -EPROBE_DEFER;
             goto cleanup_pinctrl_state;
         }
         if (!IS_ERR(gpiod)) {
             bri->scl_gpiod = gpiod;
             bri->recover_bus = i2c_generic_scl_recovery;
             dev_info(dev, "using generic GPIOs for recovery\n");
         }
     }
 
     /* SDA GPIOD line is optional, so we care about DEFER only */
     if (!bri->sda_gpiod) {
         /*
          * We have SCL. Pull SCL low and wait a bit so that SDA glitches
          * have no effect.
          */
         gpiod_direction_output(bri->scl_gpiod, 0);
         udelay(10);
         gpiod = devm_gpiod_get(dev, "sda", GPIOD_IN);
 
         /* Wait a bit in case of a SDA glitch, and then release SCL. */
         udelay(10);
         gpiod_direction_output(bri->scl_gpiod, 1);
 
         if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
             ret = -EPROBE_DEFER;
             goto cleanup_pinctrl_state;
         }
         if (!IS_ERR(gpiod))
             bri->sda_gpiod = gpiod;
     }
 
 cleanup_pinctrl_state:
     /* change the state of the pins back to their default state */
     if (bri->pinctrl)
         pinctrl_select_state(bri->pinctrl, bri->pins_default);
 
     return ret;
 }
 
 static int i2c_gpio_init_recovery(struct i2c_adapter *adap)
 {
     i2c_gpio_init_pinctrl_recovery(adap);
     return i2c_gpio_init_generic_recovery(adap);
 }
 
 static int i2c_init_recovery(struct i2c_adapter *adap)
 {
     struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
     bool is_error_level = true;
     char *err_str;
 
     if (!bri)
         return 0;
 
     if (i2c_gpio_init_recovery(adap) == -EPROBE_DEFER)
         return -EPROBE_DEFER;
 
     if (!bri->recover_bus) {
         err_str = "no suitable method provided";
         is_error_level = false;
         goto err;
     }
 
     if (bri->scl_gpiod && bri->recover_bus == i2c_generic_scl_recovery) {
         bri->get_scl = get_scl_gpio_value;
         bri->set_scl = set_scl_gpio_value;
         if (bri->sda_gpiod) {
             bri->get_sda = get_sda_gpio_value;
             /* FIXME: add proper flag instead of '0' once available */
             if (gpiod_get_direction(bri->sda_gpiod) == 0)
                 bri->set_sda = set_sda_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;
         }
         if (!bri->set_sda && !bri->get_sda) {
             err_str = "either get_sda() or set_sda() needed";
             goto err;
         }
     }
 
     return 0;
  err:
     if (is_error_level)
         dev_err(&adap->dev, "Not using recovery: %s\n", err_str);
     else
         dev_dbg(&adap->dev, "Not using recovery: %s\n", err_str);
     adap->bus_recovery_info = NULL;
 
     return -EINVAL;
 }
 
 static int i2c_smbus_host_notify_to_irq(const struct i2c_client *client)
 {
     struct i2c_adapter *adap = client->adapter;
     unsigned int irq;
 
     if (!adap->host_notify_domain)
         return -ENXIO;
 
     if (client->flags & I2C_CLIENT_TEN)
         return -EINVAL;
 
     irq = irq_create_mapping(adap->host_notify_domain, client->addr);
 
     return irq > 0 ? irq : -ENXIO;
 }
 
 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;
 
     client->irq = client->init_irq;
 
     if (!client->irq) {
         int irq = -ENOENT;
 
         if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
             dev_dbg(dev, "Using Host Notify IRQ\n");
             /* Keep adapter active when Host Notify is required */
             pm_runtime_get_sync(&client->adapter->dev);
             irq = i2c_smbus_host_notify_to_irq(client);
         } else 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 = i2c_acpi_get_irq(client);
         }
         if (irq == -EPROBE_DEFER) {
             status = irq;
             goto put_sync_adapter;
         }
 
         if (irq < 0)
             irq = 0;
 
         client->irq = irq;
     }
 
     driver = to_i2c_driver(dev->driver);
 
     /*
      * An I2C ID table is not mandatory, if and only if, a suitable OF
      * or ACPI ID table is supplied for the probing device.
      */
     if (!driver->id_table &&
         !acpi_driver_match_device(dev, dev->driver) &&
         !i2c_of_match_device(dev->driver->of_match_table, client)) {
         status = -ENODEV;
         goto put_sync_adapter;
     }
 
     if (client->flags & I2C_CLIENT_WAKE) {
         int wakeirq;
 
         wakeirq = of_irq_get_byname(dev->of_node, "wakeup");
         if (wakeirq == -EPROBE_DEFER) {
             status = wakeirq;
             goto put_sync_adapter;
         }
 
         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\n");
     }
 
     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,
                       !i2c_acpi_waive_d0_probe(dev));
     if (status)
         goto err_clear_wakeup_irq;
 
     client->devres_group_id = devres_open_group(&client->dev, NULL,
                             GFP_KERNEL);
     if (!client->devres_group_id) {
         status = -ENOMEM;
         goto err_detach_pm_domain;
     }
 
     /*
      * When there are no more users of probe(),
      * rename probe_new to probe.
      */
     if (driver->probe_new)
         status = driver->probe_new(client);
     else if (driver->probe)
         status = driver->probe(client,
                        i2c_match_id(driver->id_table, client));
     else
         status = -EINVAL;
 
     /*
      * Note that we are not closing the devres group opened above so
      * even resources that were attached to the device after probe is
      * run are released when i2c_device_remove() is executed. This is
      * needed as some drivers would allocate additional resources,
      * for example when updating firmware.
      */
 
     if (status)
         goto err_release_driver_resources;
 
     return 0;
 
 err_release_driver_resources:
     devres_release_group(&client->dev, client->devres_group_id);
 err_detach_pm_domain:
     dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
 err_clear_wakeup_irq:
     dev_pm_clear_wake_irq(&client->dev);
     device_init_wakeup(&client->dev, false);
 put_sync_adapter:
     if (client->flags & I2C_CLIENT_HOST_NOTIFY)
         pm_runtime_put_sync(&client->adapter->dev);
 
     return status;
 }
 
 static void i2c_device_remove(struct device *dev)
 {
     struct i2c_client   *client = to_i2c_client(dev);
     struct i2c_driver   *driver;
 
     driver = to_i2c_driver(dev->driver);
     if (driver->remove) {
         int status;
 
         dev_dbg(dev, "remove\n");
 
         status = driver->remove(client);
         if (status)
             dev_warn(dev, "remove failed (%pe), will be ignored\n", ERR_PTR(status));
     }
 
     devres_release_group(&client->dev, client->devres_group_id);
 
     dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
 
     dev_pm_clear_wake_irq(&client->dev);
     device_init_wakeup(&client->dev, false);
 
     client->irq = 0;
     if (client->flags & I2C_CLIENT_HOST_NOTIFY)
         pm_runtime_put(&client->adapter->dev);
 }
 
 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);
     else if (client->irq > 0)
         disable_irq(client->irq);
 }
 
 static void i2c_client_dev_release(struct device *dev)
 {
     kfree(to_i2c_client(dev));
 }
 
 static ssize_t
 name_show(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_RO(name);
 
 static ssize_t
 modalias_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
     struct i2c_client *client = to_i2c_client(dev);
     int len;
 
     len = of_device_modalias(dev, buf, PAGE_SIZE);
     if (len != -ENODEV)
         return 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_RO(modalias);
 
 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);
 
 struct device_type i2c_client_type = {
     .groups     = i2c_dev_groups,
     .uevent     = i2c_device_uevent,
     .release    = i2c_client_dev_release,
 };
 EXPORT_SYMBOL_GPL(i2c_client_type);
 
 
 /**
  * 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 int 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. */
 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_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
 }
 
 /**
  * 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 i2c_board_info const *info)
 {
     struct acpi_device *adev = ACPI_COMPANION(&client->dev);
 
     if (info && info->dev_name) {
         dev_set_name(&client->dev, "i2c-%s", info->dev_name);
         return;
     }
 
     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));
 }
 
 int i2c_dev_irq_from_resources(const struct resource *resources,
                    unsigned int num_resources)
 {
     struct irq_data *irqd;
     int i;
 
     for (i = 0; i < num_resources; i++) {
         const struct resource *r = &resources[i];
 
         if (resource_type(r) != IORESOURCE_IRQ)
             continue;
 
         if (r->flags & IORESOURCE_BITS) {
             irqd = irq_get_irq_data(r->start);
             if (!irqd)
                 break;
 
             irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
         }
 
         return r->start;
     }
 
     return 0;
 }
 
 /**
  * i2c_new_client_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 an ERR_PTR to describe the error.
  */
 struct i2c_client *
 i2c_new_client_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 ERR_PTR(-ENOMEM);
 
     client->adapter = adap;
 
     client->dev.platform_data = info->platform_data;
     client->flags = info->flags;
     client->addr = info->addr;
 
     client->init_irq = info->irq;
     if (!client->init_irq)
         client->init_irq = i2c_dev_irq_from_resources(info->resources,
                              info->num_resources);
 
     strscpy(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 = of_node_get(info->of_node);
     client->dev.fwnode = info->fwnode;
 
     device_enable_async_suspend(&client->dev);
     i2c_dev_set_name(adap, client, info);
 
     if (info->swnode) {
         status = device_add_software_node(&client->dev, info->swnode);
         if (status) {
             dev_err(&adap->dev,
                 "Failed to add software node to client %s: %d\n",
                 client->name, status);
             goto out_err_put_of_node;
         }
     }
 
     status = device_register(&client->dev);
     if (status)
         goto out_remove_swnode;
 
     dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
         client->name, dev_name(&client->dev));
 
     return client;
 
 out_remove_swnode:
     device_remove_software_node(&client->dev);
 out_err_put_of_node:
     of_node_put(info->of_node);
 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 ERR_PTR(status);
 }
 EXPORT_SYMBOL_GPL(i2c_new_client_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 (IS_ERR_OR_NULL(client))
         return;
 
     if (client->dev.of_node) {
         of_node_clear_flag(client->dev.of_node, OF_POPULATED);
         of_node_put(client->dev.of_node);
     }
 
     if (ACPI_COMPANION(&client->dev))
         acpi_device_clear_enumerated(ACPI_COMPANION(&client->dev));
     device_remove_software_node(&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 struct i2c_driver dummy_driver = {
     .driver.name    = "dummy",
     .probe      = dummy_probe,
     .id_table   = dummy_id,
 };
 
 /**
  * i2c_new_dummy_device - 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 an ERR_PTR to describe the error.
  */
 struct i2c_client *i2c_new_dummy_device(struct i2c_adapter *adapter, u16 address)
 {
     struct i2c_board_info info = {
         I2C_BOARD_INFO("dummy", address),
     };
 
     return i2c_new_client_device(adapter, &info);
 }
 EXPORT_SYMBOL_GPL(i2c_new_dummy_device);
 
 static void devm_i2c_release_dummy(void *client)
 {
     i2c_unregister_device(client);
 }
 
 /**
  * devm_i2c_new_dummy_device - return a new i2c device bound to a dummy driver
  * @dev: device the managed resource is bound to
  * @adapter: the adapter managing the device
  * @address: seven bit address to be used
  * Context: can sleep
  *
  * This is the device-managed version of @i2c_new_dummy_device. It returns the
  * new i2c client or an ERR_PTR in case of an error.
  */
 struct i2c_client *devm_i2c_new_dummy_device(struct device *dev,
                          struct i2c_adapter *adapter,
                          u16 address)
 {
     struct i2c_client *client;
     int ret;
 
     client = i2c_new_dummy_device(adapter, address);
     if (IS_ERR(client))
         return client;
 
     ret = devm_add_action_or_reset(dev, devm_i2c_release_dummy, client);
     if (ret)
         return ERR_PTR(ret);
 
     return client;
 }
 EXPORT_SYMBOL_GPL(devm_i2c_new_dummy_device);
 
 /**
  * i2c_new_ancillary_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 an ERR_PTR to describe the error.
  */
 struct i2c_client *i2c_new_ancillary_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_device(client->adapter, addr);
 }
 EXPORT_SYMBOL_GPL(i2c_new_ancillary_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);
 }
 
 unsigned int i2c_adapter_depth(struct i2c_adapter *adapter)
 {
     unsigned int depth = 0;
 
     while ((adapter = i2c_parent_is_i2c_adapter(adapter)))
         depth++;
 
     WARN_ONCE(depth >= MAX_LOCKDEP_SUBCLASSES,
           "adapter depth exceeds lockdep subclass limit\n");
 
     return depth;
 }
 EXPORT_SYMBOL_GPL(i2c_adapter_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
 new_device_store(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_client_device(adap, &info);
     if (IS_ERR(client))
         return PTR_ERR(client);
 
     /* 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_WO(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
 delete_device_store(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,
                   delete_device_store);
 
 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 &&
             IS_ERR(i2c_new_client_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);
 }
 
 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);
 
     return 0;
 }
 
 static int __process_new_adapter(struct device_driver *d, void *data)
 {
     return i2c_do_add_adapter(to_i2c_driver(d), data);
 }
 
 static const struct i2c_lock_operations i2c_adapter_lock_ops = {
     .lock_bus =    i2c_adapter_lock_bus,
     .trylock_bus = i2c_adapter_trylock_bus,
     .unlock_bus =  i2c_adapter_unlock_bus,
 };
 
 static void i2c_host_notify_irq_teardown(struct i2c_adapter *adap)
 {
     struct irq_domain *domain = adap->host_notify_domain;
     irq_hw_number_t hwirq;
 
     if (!domain)
         return;
 
     for (hwirq = 0 ; hwirq < I2C_ADDR_7BITS_COUNT ; hwirq++)
         irq_dispose_mapping(irq_find_mapping(domain, hwirq));
 
     irq_domain_remove(domain);
     adap->host_notify_domain = NULL;
 }
 
 static int i2c_host_notify_irq_map(struct irq_domain *h,
                       unsigned int virq,
                       irq_hw_number_t hw_irq_num)
 {
     irq_set_chip_and_handler(virq, &dummy_irq_chip, handle_simple_irq);
 
     return 0;
 }
 
 static const struct irq_domain_ops i2c_host_notify_irq_ops = {
     .map = i2c_host_notify_irq_map,
 };
 
 static int i2c_setup_host_notify_irq_domain(struct i2c_adapter *adap)
 {
     struct irq_domain *domain;
 
     if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_HOST_NOTIFY))
         return 0;
 
     domain = irq_domain_create_linear(adap->dev.parent->fwnode,
                       I2C_ADDR_7BITS_COUNT,
                       &i2c_host_notify_irq_ops, adap);
     if (!domain)
         return -ENOMEM;
 
     adap->host_notify_domain = domain;
 
     return 0;
 }
 
 /**
  * i2c_handle_smbus_host_notify - Forward a Host Notify event to the correct
  * I2C client.
  * @adap: the adapter
  * @addr: the I2C address of the notifying device
  * Context: can't sleep
  *
  * Helper function to be called from an I2C bus driver's interrupt
  * handler. It will schedule the Host Notify IRQ.
  */
 int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr)
 {
     int irq;
 
     if (!adap)
         return -EINVAL;
 
     irq = irq_find_mapping(adap->host_notify_domain, addr);
     if (irq <= 0)
         return -ENXIO;
 
     generic_handle_irq_safe(irq);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(i2c_handle_smbus_host_notify);
 
 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_ops)
         adap->lock_ops = &i2c_adapter_lock_ops;
 
     adap->locked_flags = 0;
     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;
 
     /* register soft irqs for Host Notify */
     res = i2c_setup_host_notify_irq_domain(adap);
     if (res) {
         pr_err("adapter '%s': can't create Host Notify IRQs (%d)\n",
                adap->name, res);
         goto out_list;
     }
 
     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;
     }
 
     res = i2c_setup_smbus_alert(adap);
     if (res)
         goto out_reg;
 
     device_enable_async_suspend(&adap->dev);
     pm_runtime_no_callbacks(&adap->dev);
     pm_suspend_ignore_children(&adap->dev, true);
     pm_runtime_enable(&adap->dev);
 
     res = i2c_init_recovery(adap);
     if (res == -EPROBE_DEFER)
         goto out_reg;
 
     dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
 
 #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
 
     /* create pre-declared device nodes */
     of_i2c_register_devices(adap);
     i2c_acpi_install_space_handler(adap);
     i2c_acpi_register_devices(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_reg:
     init_completion(&adap->dev_released);
     device_unregister(&adap->dev);
     wait_for_completion(&adap->dev_released);
 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);
     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 unregistered
  * Context: can sleep
  *
  * This unregisters an I2C adapter which was previously registered
  * by @i2c_add_adapter or @i2c_add_numbered_adapter.
  */
 void i2c_del_adapter(struct i2c_adapter *adap)
 {
     struct i2c_adapter *found;
     struct i2c_client *client, *next;
 
     /* First make sure that this adapter was ever added */
     mutex_lock(&core_lock);
     found = idr_find(&i2c_adapter_idr, adap->nr);
     mutex_unlock(&core_lock);
     if (found != adap) {
         pr_debug("attempting to delete unregistered adapter [%s]\n", adap->name);
         return;
     }
 
     i2c_acpi_remove_space_handler(adap);
     /* Tell drivers about this removal */
     mutex_lock(&core_lock);
     bus_for_each_drv(&i2c_bus_type, NULL, adap,
                    __process_removed_adapter);
     mutex_unlock(&core_lock);
 
     /* Remove devices instantiated from sysfs */
     mutex_lock_nested(&adap->userspace_clients_lock,
               i2c_adapter_depth(adap));
     list_for_each_entry_safe(client, next, &adap->userspace_clients,
                  detected) {
         dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
             client->addr);
         list_del(&client->detected);
         i2c_unregister_device(client);
     }
     mutex_unlock(&adap->userspace_clients_lock);
 
     /* Detach any active clients. This can't fail, thus we do not
      * check the returned value. This is a two-pass process, because
      * we can't remove the dummy devices during the first pass: they
      * could have been instantiated by real devices wishing to clean
      * them up properly, so we give them a chance to do that first. */
     device_for_each_child(&adap->dev, NULL, __unregister_client);
     device_for_each_child(&adap->dev, NULL, __unregister_dummy);
 
 #ifdef CONFIG_I2C_COMPAT
     class_compat_remove_link(i2c_adapter_compat_class, &adap->dev,
                  adap->dev.parent);
 #endif
 
     /* device name is gone after device_unregister */
     dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);
 
     pm_runtime_disable(&adap->dev);
 
     i2c_host_notify_irq_teardown(adap);
 
     /* wait until all references to the device are gone
      *
      * FIXME: This is old code and should ideally be replaced by an
      * alternative which results in decoupling the lifetime of the struct
      * device from the i2c_adapter, like spi or netdev do. Any solution
      * should be thoroughly tested with DEBUG_KOBJECT_RELEASE enabled!
      */
     init_completion(&adap->dev_released);
     device_unregister(&adap->dev);
     wait_for_completion(&adap->dev_released);
 
     /* free bus id */
     mutex_lock(&core_lock);
     idr_remove(&i2c_adapter_idr, adap->nr);
     mutex_unlock(&core_lock);
 
     /* Clear the device structure in case this adapter is ever going to be
        added again */
     memset(&adap->dev, 0, sizeof(adap->dev));
 }
 EXPORT_SYMBOL(i2c_del_adapter);
 
 static void devm_i2c_del_adapter(void *adapter)
 {
     i2c_del_adapter(adapter);
 }
 
 /**
  * devm_i2c_add_adapter - device-managed variant of i2c_add_adapter()
  * @dev: managing device for adding this I2C adapter
  * @adapter: the adapter to add
  * Context: can sleep
  *
  * Add adapter with dynamic bus number, same with i2c_add_adapter()
  * but the adapter will be auto deleted on driver detach.
  */
 int devm_i2c_add_adapter(struct device *dev, struct i2c_adapter *adapter)
 {
     int ret;
 
     ret = i2c_add_adapter(adapter);
     if (ret)
         return ret;
 
     return devm_add_action_or_reset(dev, devm_i2c_del_adapter, adapter);
 }
 EXPORT_SYMBOL_GPL(devm_i2c_add_adapter);
 
 static void i2c_parse_timing(struct device *dev, char *prop_name, u32 *cur_val_p,
                 u32 def_val, bool use_def)
 {
     int ret;
 
     ret = device_property_read_u32(dev, prop_name, cur_val_p);
     if (ret && use_def)
         *cur_val_p = def_val;
 
     dev_dbg(dev, "%s: %u\n", prop_name, *cur_val_p);
 }
 
 /**
  * i2c_parse_fw_timings - get I2C related timing parameters from firmware
  * @dev: The device to scan for I2C timing properties
  * @t: the i2c_timings struct to be filled with values
  * @use_defaults: bool to use sane defaults derived from the I2C specification
  *        when properties are not found, otherwise don't update
  *
  * Scan the device for the generic I2C properties describing timing parameters
  * for the signal and fill the given struct with the results. If a property was
  * not found and use_defaults was true, then maximum timings are assumed which
  * are derived from the I2C specification. If use_defaults is not used, the
  * results will be as before, so drivers can apply their own defaults before
  * calling this helper. The latter is mainly intended for avoiding regressions
  * of existing drivers which want to switch to this function. New drivers
  * almost always should use the defaults.
  */
 void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults)
 {
     bool u = use_defaults;
     u32 d;
 
     i2c_parse_timing(dev, "clock-frequency", &t->bus_freq_hz,
              I2C_MAX_STANDARD_MODE_FREQ, u);
 
     d = t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ ? 1000 :
         t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ ? 300 : 120;
     i2c_parse_timing(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns, d, u);
 
     d = t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ ? 300 : 120;
     i2c_parse_timing(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns, d, u);
 
     i2c_parse_timing(dev, "i2c-scl-internal-delay-ns",
              &t->scl_int_delay_ns, 0, u);
     i2c_parse_timing(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns,
              t->scl_fall_ns, u);
     i2c_parse_timing(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns, 0, u);
     i2c_parse_timing(dev, "i2c-digital-filter-width-ns",
              &t->digital_filter_width_ns, 0, u);
     i2c_parse_timing(dev, "i2c-analog-filter-cutoff-frequency",
              &t->analog_filter_cutoff_freq_hz, 0, u);
 }
 EXPORT_SYMBOL_GPL(i2c_parse_fw_timings);
 
 /* ------------------------------------------------------------------------- */
 
 int i2c_for_each_dev(void *data, int (*fn)(struct device *dev, void *data))
 {
     int res;
 
     mutex_lock(&core_lock);
     res = bus_for_each_dev(&i2c_bus_type, NULL, data, fn);
     mutex_unlock(&core_lock);
 
     return res;
 }
 EXPORT_SYMBOL_GPL(i2c_for_each_dev);
 
 static int __process_new_driver(struct device *dev, void *data)
 {
     if (dev->type != &i2c_adapter_type)
         return 0;
     return i2c_do_add_adapter(data, to_i2c_adapter(dev));
 }
 
 /*
  * An i2c_driver is used with one or more i2c_client (device) nodes to access
  * i2c slave chips, on a bus instance associated with some i2c_adapter.
  */
 
 int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 {
     int res;
 
     /* Can't register until after driver model init */
     if (WARN_ON(!is_registered))
         return -EAGAIN;
 
     /* add the driver to the list of i2c drivers in the driver core */
     driver->driver.owner = owner;
     driver->driver.bus = &i2c_bus_type;
     INIT_LIST_HEAD(&driver->clients);
 
     /* When registration returns, the driver core
      * will have called probe() for all matching-but-unbound devices.
      */
     res = driver_register(&driver->driver);
     if (res)
         return res;
 
     pr_debug("driver [%s] registered\n", driver->driver.name);
 
     /* Walk the adapters that are already present */
     i2c_for_each_dev(driver, __process_new_driver);
 
     return 0;
 }
 EXPORT_SYMBOL(i2c_register_driver);
 
 static int __process_removed_driver(struct device *dev, void *data)
 {
     if (dev->type == &i2c_adapter_type)
         i2c_do_del_adapter(data, to_i2c_adapter(dev));
     return 0;
 }
 
 /**
  * i2c_del_driver - unregister I2C driver
  * @driver: the driver being unregistered
  * Context: can sleep
  */
 void i2c_del_driver(struct i2c_driver *driver)
 {
     i2c_for_each_dev(driver, __process_removed_driver);
 
     driver_unregister(&driver->driver);
     pr_debug("driver [%s] unregistered\n", driver->driver.name);
 }
 EXPORT_SYMBOL(i2c_del_driver);
 
 /* ------------------------------------------------------------------------- */
 
 struct i2c_cmd_arg {
     unsigned    cmd;
     void        *arg;
 };
 
 static int i2c_cmd(struct device *dev, void *_arg)
 {
     struct i2c_client   *client = i2c_verify_client(dev);
     struct i2c_cmd_arg  *arg = _arg;
     struct i2c_driver   *driver;
 
     if (!client || !client->dev.driver)
         return 0;
 
     driver = to_i2c_driver(client->dev.driver);
     if (driver->command)
         driver->command(client, arg->cmd, arg->arg);
     return 0;
 }
 
 void i2c_clients_command(struct i2c_adapter *adap, unsigned int cmd, void *arg)
 {
     struct i2c_cmd_arg  cmd_arg;
 
     cmd_arg.cmd = cmd;
     cmd_arg.arg = arg;
     device_for_each_child(&adap->dev, &cmd_arg, i2c_cmd);
 }
 EXPORT_SYMBOL(i2c_clients_command);
 
 static int __init i2c_init(void)
 {
     int retval;
 
     retval = of_alias_get_highest_id("i2c");
 
     down_write(&__i2c_board_lock);
     if (retval >= __i2c_first_dynamic_bus_num)
         __i2c_first_dynamic_bus_num = retval + 1;
     up_write(&__i2c_board_lock);
 
     retval = bus_register(&i2c_bus_type);
     if (retval)
         return retval;
 
     is_registered = true;
 
 #ifdef CONFIG_I2C_COMPAT
     i2c_adapter_compat_class = class_compat_register("i2c-adapter");
     if (!i2c_adapter_compat_class) {
         retval = -ENOMEM;
         goto bus_err;
     }
 #endif
     retval = i2c_add_driver(&dummy_driver);
     if (retval)
         goto class_err;
 
     if (IS_ENABLED(CONFIG_OF_DYNAMIC))
         WARN_ON(of_reconfig_notifier_register(&i2c_of_notifier));
     if (IS_ENABLED(CONFIG_ACPI))
         WARN_ON(acpi_reconfig_notifier_register(&i2c_acpi_notifier));
 
     return 0;
 
 class_err:
 #ifdef CONFIG_I2C_COMPAT
     class_compat_unregister(i2c_adapter_compat_class);
 bus_err:
 #endif
     is_registered = false;
     bus_unregister(&i2c_bus_type);
     return retval;
 }
 
 static void __exit i2c_exit(void)
 {
     if (IS_ENABLED(CONFIG_ACPI))
         WARN_ON(acpi_reconfig_notifier_unregister(&i2c_acpi_notifier));
     if (IS_ENABLED(CONFIG_OF_DYNAMIC))
         WARN_ON(of_reconfig_notifier_unregister(&i2c_of_notifier));
     i2c_del_driver(&dummy_driver);
 #ifdef CONFIG_I2C_COMPAT
     class_compat_unregister(i2c_adapter_compat_class);
 #endif
     bus_unregister(&i2c_bus_type);
     tracepoint_synchronize_unregister();
 }
 
 /* We must initialize early, because some subsystems register i2c drivers
  * in subsys_initcall() code, but are linked (and initialized) before i2c.
  */
 postcore_initcall(i2c_init);
 module_exit(i2c_exit);
 
 /* ----------------------------------------------------
  * the functional interface to the i2c busses.
  * ----------------------------------------------------
  */
 
 /* Check if val is exceeding the quirk IFF quirk is non 0 */
 #define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
 
 static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
 {
     dev_err_ratelimited(&adap->dev, "adapter quirk: %s (addr 0x%04x, size %u, %s)\n",
                 err_msg, msg->addr, msg->len,
                 msg->flags & I2C_M_RD ? "read" : "write");
     return -EOPNOTSUPP;
 }
 
 static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
     const struct i2c_adapter_quirks *q = adap->quirks;
     int max_num = q->max_num_msgs, i;
     bool do_len_check = true;
 
     if (q->flags & I2C_AQ_COMB) {
         max_num = 2;
 
         /* special checks for combined messages */
         if (num == 2) {
             if (q->flags & I2C_AQ_COMB_WRITE_FIRST && msgs[0].flags & I2C_M_RD)
                 return i2c_quirk_error(adap, &msgs[0], "1st comb msg must be write");
 
             if (q->flags & I2C_AQ_COMB_READ_SECOND && !(msgs[1].flags & I2C_M_RD))
                 return i2c_quirk_error(adap, &msgs[1], "2nd comb msg must be read");
 
             if (q->flags & I2C_AQ_COMB_SAME_ADDR && msgs[0].addr != msgs[1].addr)
                 return i2c_quirk_error(adap, &msgs[0], "comb msg only to same addr");
 
             if (i2c_quirk_exceeded(msgs[0].len, q->max_comb_1st_msg_len))
                 return i2c_quirk_error(adap, &msgs[0], "msg too long");
 
             if (i2c_quirk_exceeded(msgs[1].len, q->max_comb_2nd_msg_len))
                 return i2c_quirk_error(adap, &msgs[1], "msg too long");
 
             do_len_check = false;
         }
     }
 
     if (i2c_quirk_exceeded(num, max_num))
         return i2c_quirk_error(adap, &msgs[0], "too many messages");
 
     for (i = 0; i < num; i++) {
         u16 len = msgs[i].len;
 
         if (msgs[i].flags & I2C_M_RD) {
             if (do_len_check && i2c_quirk_exceeded(len, q->max_read_len))
                 return i2c_quirk_error(adap, &msgs[i], "msg too long");
 
             if (q->flags & I2C_AQ_NO_ZERO_LEN_READ && len == 0)
                 return i2c_quirk_error(adap, &msgs[i], "no zero length");
         } else {
             if (do_len_check && i2c_quirk_exceeded(len, q->max_write_len))
                 return i2c_quirk_error(adap, &msgs[i], "msg too long");
 
             if (q->flags & I2C_AQ_NO_ZERO_LEN_WRITE && len == 0)
                 return i2c_quirk_error(adap, &msgs[i], "no zero length");
         }
     }
 
     return 0;
 }
 
 /**
  * __i2c_transfer - unlocked flavor of i2c_transfer
  * @adap: Handle to I2C bus
  * @msgs: One or more messages to execute before STOP is issued to
  *  terminate the operation; each message begins with a START.
  * @num: Number of messages to be executed.
  *
  * Returns negative errno, else the number of messages executed.
  *
  * Adapter lock must be held when calling this function. No debug logging
  * takes place. adap->algo->master_xfer existence isn't checked.
  */
 int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
     unsigned long orig_jiffies;
     int ret, try;
 
     if (WARN_ON(!msgs || num < 1))
         return -EINVAL;
 
     ret = __i2c_check_suspended(adap);
     if (ret)
         return ret;
 
     if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
         return -EOPNOTSUPP;
 
     /*
      * i2c_trace_msg_key gets enabled when tracepoint i2c_transfer gets
      * enabled.  This is an efficient way of keeping the for-loop from
      * being executed when not needed.
      */
     if (static_branch_unlikely(&i2c_trace_msg_key)) {
         int i;
         for (i = 0; i < num; i++)
             if (msgs[i].flags & I2C_M_RD)
                 trace_i2c_read(adap, &msgs[i], i);
             else
                 trace_i2c_write(adap, &msgs[i], i);
     }
 
     /* Retry automatically on arbitration loss */
     orig_jiffies = jiffies;
     for (ret = 0, try = 0; try <= adap->retries; try++) {
         if (i2c_in_atomic_xfer_mode() && adap->algo->master_xfer_atomic)
             ret = adap->algo->master_xfer_atomic(adap, msgs, num);
         else
             ret = adap->algo->master_xfer(adap, msgs, num);
 
         if (ret != -EAGAIN)
             break;
         if (time_after(jiffies, orig_jiffies + adap->timeout))
             break;
     }
 
     if (static_branch_unlikely(&i2c_trace_msg_key)) {
         int i;
         for (i = 0; i < ret; i++)
             if (msgs[i].flags & I2C_M_RD)
                 trace_i2c_reply(adap, &msgs[i], i);
         trace_i2c_result(adap, num, ret);
     }
 
     return ret;
 }
 EXPORT_SYMBOL(__i2c_transfer);
 
 /**
  * i2c_transfer - execute a single or combined I2C message
  * @adap: Handle to I2C bus
  * @msgs: One or more messages to execute before STOP is issued to
  *  terminate the operation; each message begins with a START.
  * @num: Number of messages to be executed.
  *
  * Returns negative errno, else the number of messages executed.
  *
  * Note that there is no requirement that each message be sent to
  * the same slave address, although that is the most common model.
  */
 int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
     int ret;
 
     if (!adap->algo->master_xfer) {
         dev_dbg(&adap->dev, "I2C level transfers not supported\n");
         return -EOPNOTSUPP;
     }
 
     /* REVISIT the fault reporting model here is weak:
      *
      *  - When we get an error after receiving N bytes from a slave,
      *    there is no way to report "N".
      *
      *  - When we get a NAK after transmitting N bytes to a slave,
      *    there is no way to report "N" ... or to let the master
      *    continue executing the rest of this combined message, if
      *    that's the appropriate response.
      *
      *  - When for example "num" is two and we successfully complete
      *    the first message but get an error part way through the
      *    second, it's unclear whether that should be reported as
      *    one (discarding status on the second message) or errno
      *    (discarding status on the first one).
      */
     ret = __i2c_lock_bus_helper(adap);
     if (ret)
         return ret;
 
     ret = __i2c_transfer(adap, msgs, num);
     i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);
 
     return ret;
 }
 EXPORT_SYMBOL(i2c_transfer);
 
 /**
  * i2c_transfer_buffer_flags - issue a single I2C message transferring data
  *                 to/from a buffer
  * @client: Handle to slave device
  * @buf: Where the data is stored
  * @count: How many bytes to transfer, must be less than 64k since msg.len is u16
  * @flags: The flags to be used for the message, e.g. I2C_M_RD for reads
  *
  * Returns negative errno, or else the number of bytes transferred.
  */
 int i2c_transfer_buffer_flags(const struct i2c_client *client, char *buf,
                   int count, u16 flags)
 {
     int ret;
     struct i2c_msg msg = {
         .addr = client->addr,
         .flags = flags | (client->flags & I2C_M_TEN),
         .len = count,
         .buf = buf,
     };
 
     ret = i2c_transfer(client->adapter, &msg, 1);
 
     /*
      * If everything went ok (i.e. 1 msg transferred), return #bytes
      * transferred, else error code.
      */
     return (ret == 1) ? count : ret;
 }
 EXPORT_SYMBOL(i2c_transfer_buffer_flags);
 
 /**
  * i2c_get_device_id - get manufacturer, part id and die revision of a device
  * @client: The device to query
  * @id: The queried information
  *
  * Returns negative errno on error, zero on success.
  */
 int i2c_get_device_id(const struct i2c_client *client,
               struct i2c_device_identity *id)
 {
     struct i2c_adapter *adap = client->adapter;
     union i2c_smbus_data raw_id;
     int ret;
 
     if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
         return -EOPNOTSUPP;
 
     raw_id.block[0] = 3;
     ret = i2c_smbus_xfer(adap, I2C_ADDR_DEVICE_ID, 0,
                  I2C_SMBUS_READ, client->addr << 1,
                  I2C_SMBUS_I2C_BLOCK_DATA, &raw_id);
     if (ret)
         return ret;
 
     id->manufacturer_id = (raw_id.block[1] << 4) | (raw_id.block[2] >> 4);
     id->part_id = ((raw_id.block[2] & 0xf) << 5) | (raw_id.block[3] >> 3);
     id->die_revision = raw_id.block[3] & 0x7;
     return 0;
 }
 EXPORT_SYMBOL_GPL(i2c_get_device_id);
 
 /* ----------------------------------------------------
  * the i2c address scanning function
  * Will not work for 10-bit addresses!
  * ----------------------------------------------------
  */
 
 /*
  * Legacy default probe function, mostly relevant for SMBus. The default
  * probe method is a quick write, but it is known to corrupt the 24RF08
  * EEPROMs due to a state machine bug, and could also irreversibly
  * write-protect some EEPROMs, so for address ranges 0x30-0x37 and 0x50-0x5f,
  * we use a short byte read instead. Also, some bus drivers don't implement
  * quick write, so we fallback to a byte read in that case too.
  * On x86, there is another special case for FSC hardware monitoring chips,
  * which want regular byte reads (address 0x73.) Fortunately, these are the
  * only known chips using this I2C address on PC hardware.
  * Returns 1 if probe succeeded, 0 if not.
  */
 static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
 {
     int err;
     union i2c_smbus_data dummy;
 
 #ifdef CONFIG_X86
     if (addr == 0x73 && (adap->class & I2C_CLASS_HWMON)
      && i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE_DATA))
         err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                      I2C_SMBUS_BYTE_DATA, &dummy);
     else
 #endif
     if (!((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50)
      && i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
         err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0,
                      I2C_SMBUS_QUICK, NULL);
     else if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE))
         err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                      I2C_SMBUS_BYTE, &dummy);
     else {
         dev_warn(&adap->dev, "No suitable probing method supported for address 0x%02X\n",
              addr);
         err = -EOPNOTSUPP;
     }
 
     return err >= 0;
 }
 
 static int i2c_detect_address(struct i2c_client *temp_client,
                   struct i2c_driver *driver)
 {
     struct i2c_board_info info;
     struct i2c_adapter *adapter = temp_client->adapter;
     int addr = temp_client->addr;
     int err;
 
     /* Make sure the address is valid */
     err = i2c_check_7bit_addr_validity_strict(addr);
     if (err) {
         dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
              addr);
         return err;
     }
 
     /* Skip if already in use (7 bit, no need to encode flags) */
     if (i2c_check_addr_busy(adapter, addr))
         return 0;
 
     /* Make sure there is something at this address */
     if (!i2c_default_probe(adapter, addr))
         return 0;
 
     /* Finally call the custom detection function */
     memset(&info, 0, sizeof(struct i2c_board_info));
     info.addr = addr;
     err = driver->detect(temp_client, &info);
     if (err) {
         /* -ENODEV is returned if the detection fails. We catch it
            here as this isn't an error. */
         return err == -ENODEV ? 0 : err;
     }
 
     /* Consistency check */
     if (info.type[0] == '\0') {
         dev_err(&adapter->dev,
             "%s detection function provided no name for 0x%x\n",
             driver->driver.name, addr);
     } else {
         struct i2c_client *client;
 
         /* Detection succeeded, instantiate the device */
         if (adapter->class & I2C_CLASS_DEPRECATED)
             dev_warn(&adapter->dev,
                 "This adapter will soon drop class based instantiation of devices. "
                 "Please make sure client 0x%02x gets instantiated by other means. "
                 "Check 'Documentation/i2c/instantiating-devices.rst' for details.\n",
                 info.addr);
 
         dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
             info.type, info.addr);
         client = i2c_new_client_device(adapter, &info);
         if (!IS_ERR(client))
             list_add_tail(&client->detected, &driver->clients);
         else
             dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n",
                 info.type, info.addr);
     }
     return 0;
 }
 
 static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
 {
     const unsigned short *address_list;
     struct i2c_client *temp_client;
     int i, err = 0;
 
     address_list = driver->address_list;
     if (!driver->detect || !address_list)
         return 0;
 
     /* Warn that the adapter lost class based instantiation */
     if (adapter->class == I2C_CLASS_DEPRECATED) {
         dev_dbg(&adapter->dev,
             "This adapter dropped support for I2C classes and won't auto-detect %s devices anymore. "
             "If you need it, check 'Documentation/i2c/instantiating-devices.rst' for alternatives.\n",
             driver->driver.name);
         return 0;
     }
 
     /* Stop here if the classes do not match */
     if (!(adapter->class & driver->class))
         return 0;
 
     /* Set up a temporary client to help detect callback */
     temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
     if (!temp_client)
         return -ENOMEM;
     temp_client->adapter = adapter;
 
     for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
         dev_dbg(&adapter->dev,
             "found normal entry for adapter %d, addr 0x%02x\n",
             i2c_adapter_id(adapter), address_list[i]);
         temp_client->addr = address_list[i];
         err = i2c_detect_address(temp_client, driver);
         if (unlikely(err))
             break;
     }
 
     kfree(temp_client);
     return err;
 }
 
 int i2c_probe_func_quick_read(struct i2c_adapter *adap, unsigned short addr)
 {
     return i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                   I2C_SMBUS_QUICK, NULL) >= 0;
 }
 EXPORT_SYMBOL_GPL(i2c_probe_func_quick_read);
 
 struct i2c_client *
 i2c_new_scanned_device(struct i2c_adapter *adap,
                struct i2c_board_info *info,
                unsigned short const *addr_list,
                int (*probe)(struct i2c_adapter *adap, unsigned short addr))
 {
     int i;
 
     if (!probe)
         probe = i2c_default_probe;
 
     for (i = 0; addr_list[i] != I2C_CLIENT_END; i++) {
         /* Check address validity */
         if (i2c_check_7bit_addr_validity_strict(addr_list[i]) < 0) {
             dev_warn(&adap->dev, "Invalid 7-bit address 0x%02x\n",
                  addr_list[i]);
             continue;
         }
 
         /* Check address availability (7 bit, no need to encode flags) */
         if (i2c_check_addr_busy(adap, addr_list[i])) {
             dev_dbg(&adap->dev,
                 "Address 0x%02x already in use, not probing\n",
                 addr_list[i]);
             continue;
         }
 
         /* Test address responsiveness */
         if (probe(adap, addr_list[i]))
             break;
     }
 
     if (addr_list[i] == I2C_CLIENT_END) {
         dev_dbg(&adap->dev, "Probing failed, no device found\n");
         return ERR_PTR(-ENODEV);
     }
 
     info->addr = addr_list[i];
     return i2c_new_client_device(adap, info);
 }
 EXPORT_SYMBOL_GPL(i2c_new_scanned_device);
 
 struct i2c_adapter *i2c_get_adapter(int nr)
 {
     struct i2c_adapter *adapter;
 
     mutex_lock(&core_lock);
     adapter = idr_find(&i2c_adapter_idr, nr);
     if (!adapter)
         goto exit;
 
     if (try_module_get(adapter->owner))
         get_device(&adapter->dev);
     else
         adapter = NULL;
 
  exit:
     mutex_unlock(&core_lock);
     return adapter;
 }
 EXPORT_SYMBOL(i2c_get_adapter);
 
 void i2c_put_adapter(struct i2c_adapter *adap)
 {
     if (!adap)
         return;
 
     module_put(adap->owner);
     /* Should be last, otherwise we risk use-after-free with 'adap' */
     put_device(&adap->dev);
 }
 EXPORT_SYMBOL(i2c_put_adapter);
 
 /**
  * i2c_get_dma_safe_msg_buf() - get a DMA safe buffer for the given i2c_msg
  * @msg: the message to be checked
  * @threshold: the minimum number of bytes for which using DMA makes sense.
  *         Should at least be 1.
  *
  * Return: NULL if a DMA safe buffer was not obtained. Use msg->buf with PIO.
  *     Or a valid pointer to be used with DMA. After use, release it by
  *     calling i2c_put_dma_safe_msg_buf().
  *
  * This function must only be called from process context!
  */
 u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold)
 {
     /* also skip 0-length msgs for bogus thresholds of 0 */
     if (!threshold)
         pr_debug("DMA buffer for addr=0x%02x with length 0 is bogus\n",
              msg->addr);
     if (msg->len < threshold || msg->len == 0)
         return NULL;
 
     if (msg->flags & I2C_M_DMA_SAFE)
         return msg->buf;
 
     pr_debug("using bounce buffer for addr=0x%02x, len=%d\n",
          msg->addr, msg->len);
 
     if (msg->flags & I2C_M_RD)
         return kzalloc(msg->len, GFP_KERNEL);
     else
         return kmemdup(msg->buf, msg->len, GFP_KERNEL);
 }
 EXPORT_SYMBOL_GPL(i2c_get_dma_safe_msg_buf);
 
 /**
  * i2c_put_dma_safe_msg_buf - release DMA safe buffer and sync with i2c_msg
  * @buf: the buffer obtained from i2c_get_dma_safe_msg_buf(). May be NULL.
  * @msg: the message which the buffer corresponds to
  * @xferred: bool saying if the message was transferred
  */
 void i2c_put_dma_safe_msg_buf(u8 *buf, struct i2c_msg *msg, bool xferred)
 {
     if (!buf || buf == msg->buf)
         return;
 
     if (xferred && msg->flags & I2C_M_RD)
         memcpy(msg->buf, buf, msg->len);
 
     kfree(buf);
 }
 EXPORT_SYMBOL_GPL(i2c_put_dma_safe_msg_buf);
 
 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 MODULE_DESCRIPTION("I2C-Bus main module");
 MODULE_LICENSE("GPL");

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