// SPDX-License-Identifier: GPL-2.0

  /*

   * drivers/base/dd.c - The core device/driver interactions.

   *

   * This file contains the (sometimes tricky) code that controls the
   * interactions between devices and drivers, which primarily includes
   * driver binding and unbinding.

   *

   * All of this code used to exist in drivers/base/bus.c, but was
   * relocated to here in the name of compartmentalization (since it wasn't
   * strictly code just for the 'struct bus_type'.

   *

   * Copyright (c) 2002-5 Patrick Mochel
   * Copyright (c) 2002-3 Open Source Development Labs

   * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
   * Copyright (c) 2007-2009 Novell Inc.

   */

  #include <linux/debugfs.h>

  #include <linux/device.h>

  #include <linux/delay.h>

  #include <linux/dma-map-ops.h>

  #include <linux/init.h>

  #include <linux/module.h>

  #include <linux/kthread.h>

  #include <linux/wait.h>

  #include <linux/async.h>

  #include <linux/pm_runtime.h>

  #include <linux/pinctrl/devinfo.h>

  #include <linux/slab.h>

  
  #include "base.h"
  #include "power/power.h"

  /*
   * Deferred Probe infrastructure.
   *
   * Sometimes driver probe order matters, but the kernel doesn't always have
   * dependency information which means some drivers will get probed before a
   * resource it depends on is available.  For example, an SDHCI driver may
   * first need a GPIO line from an i2c GPIO controller before it can be
   * initialized.  If a required resource is not available yet, a driver can
   * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
   *
   * Deferred probe maintains two lists of devices, a pending list and an active
   * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
   * pending list.  A successful driver probe will trigger moving all devices
   * from the pending to the active list so that the workqueue will eventually
   * retry them.
   *
   * The deferred_probe_mutex must be held any time the deferred_probe_*_list

   * of the (struct device*)->p->deferred_probe pointers are manipulated

   */
  static DEFINE_MUTEX(deferred_probe_mutex);
  static LIST_HEAD(deferred_probe_pending_list);
  static LIST_HEAD(deferred_probe_active_list);

  static atomic_t deferred_trigger_count = ATOMIC_INIT(0);

  static struct dentry *deferred_devices;

  static bool initcalls_done;

  /* Save the async probe drivers' name from kernel cmdline */
  #define ASYNC_DRV_NAMES_MAX_LEN	256
  static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];

  /*

   * In some cases, like suspend to RAM or hibernation, It might be reasonable
   * to prohibit probing of devices as it could be unsafe.
   * Once defer_all_probes is true all drivers probes will be forcibly deferred.
   */
  static bool defer_all_probes;
  
  /*

   * deferred_probe_work_func() - Retry probing devices in the active list.
   */
  static void deferred_probe_work_func(struct work_struct *work)
  {
  	struct device *dev;

  	struct device_private *private;

  	/*
  	 * This block processes every device in the deferred 'active' list.
  	 * Each device is removed from the active list and passed to
  	 * bus_probe_device() to re-attempt the probe.  The loop continues
  	 * until every device in the active list is removed and retried.
  	 *
  	 * Note: Once the device is removed from the list and the mutex is
  	 * released, it is possible for the device get freed by another thread
  	 * and cause a illegal pointer dereference.  This code uses
  	 * get/put_device() to ensure the device structure cannot disappear
  	 * from under our feet.
  	 */
  	mutex_lock(&deferred_probe_mutex);
  	while (!list_empty(&deferred_probe_active_list)) {

  		private = list_first_entry(&deferred_probe_active_list,
  					typeof(*dev->p), deferred_probe);
  		dev = private->device;
  		list_del_init(&private->deferred_probe);

  
  		get_device(dev);

  		/*
  		 * Drop the mutex while probing each device; the probe path may
  		 * manipulate the deferred list
  		 */

  		mutex_unlock(&deferred_probe_mutex);

  		dev_dbg(dev, "Retrying from deferred list
  ");

  		bus_probe_device(dev);

  		mutex_lock(&deferred_probe_mutex);
  
  		put_device(dev);
  	}
  	mutex_unlock(&deferred_probe_mutex);
  }
  static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);

  void driver_deferred_probe_add(struct device *dev)

  {
  	mutex_lock(&deferred_probe_mutex);

  	if (list_empty(&dev->p->deferred_probe)) {

  		dev_dbg(dev, "Added to deferred list
  ");

  		list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);

  	}
  	mutex_unlock(&deferred_probe_mutex);
  }
  
  void driver_deferred_probe_del(struct device *dev)
  {
  	mutex_lock(&deferred_probe_mutex);

  	if (!list_empty(&dev->p->deferred_probe)) {

  		dev_dbg(dev, "Removed from deferred list
  ");

  		list_del_init(&dev->p->deferred_probe);

  		kfree(dev->p->deferred_probe_reason);
  		dev->p->deferred_probe_reason = NULL;

  	}
  	mutex_unlock(&deferred_probe_mutex);
  }
  
  static bool driver_deferred_probe_enable = false;
  /**
   * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
   *
   * This functions moves all devices from the pending list to the active
   * list and schedules the deferred probe workqueue to process them.  It
   * should be called anytime a driver is successfully bound to a device.

   *
   * Note, there is a race condition in multi-threaded probe. In the case where
   * more than one device is probing at the same time, it is possible for one
   * probe to complete successfully while another is about to defer. If the second
   * depends on the first, then it will get put on the pending list after the

   * trigger event has already occurred and will be stuck there.

   *
   * The atomic 'deferred_trigger_count' is used to determine if a successful
   * trigger has occurred in the midst of probing a driver. If the trigger count
   * changes in the midst of a probe, then deferred processing should be triggered
   * again.

   */
  static void driver_deferred_probe_trigger(void)
  {
  	if (!driver_deferred_probe_enable)
  		return;

  	/*
  	 * A successful probe means that all the devices in the pending list

  	 * should be triggered to be reprobed.  Move all the deferred devices

  	 * into the active list so they can be retried by the workqueue
  	 */

  	mutex_lock(&deferred_probe_mutex);

  	atomic_inc(&deferred_trigger_count);

  	list_splice_tail_init(&deferred_probe_pending_list,
  			      &deferred_probe_active_list);
  	mutex_unlock(&deferred_probe_mutex);

  	/*
  	 * Kick the re-probe thread.  It may already be scheduled, but it is
  	 * safe to kick it again.
  	 */

  	schedule_work(&deferred_probe_work);

  }
  
  /**

   * device_block_probing() - Block/defer device's probes

   *
   *	It will disable probing of devices and defer their probes instead.
   */
  void device_block_probing(void)
  {
  	defer_all_probes = true;
  	/* sync with probes to avoid races. */
  	wait_for_device_probe();
  }
  
  /**
   * device_unblock_probing() - Unblock/enable device's probes
   *
   *	It will restore normal behavior and trigger re-probing of deferred
   * devices.
   */
  void device_unblock_probing(void)
  {
  	defer_all_probes = false;
  	driver_deferred_probe_trigger();
  }

  /**
   * device_set_deferred_probe_reason() - Set defer probe reason message for device
   * @dev: the pointer to the struct device
   * @vaf: the pointer to va_format structure with message
   */
  void device_set_deferred_probe_reason(const struct device *dev, struct va_format *vaf)
  {
  	const char *drv = dev_driver_string(dev);
  
  	mutex_lock(&deferred_probe_mutex);
  
  	kfree(dev->p->deferred_probe_reason);
  	dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
  
  	mutex_unlock(&deferred_probe_mutex);
  }

  /*
   * deferred_devs_show() - Show the devices in the deferred probe pending list.
   */
  static int deferred_devs_show(struct seq_file *s, void *data)
  {
  	struct device_private *curr;
  
  	mutex_lock(&deferred_probe_mutex);
  
  	list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)

  		seq_printf(s, "%s\t%s", dev_name(curr->device),
  			   curr->device->p->deferred_probe_reason ?: "
  ");

  
  	mutex_unlock(&deferred_probe_mutex);
  
  	return 0;
  }
  DEFINE_SHOW_ATTRIBUTE(deferred_devs);

  int driver_deferred_probe_timeout;

  EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);

  static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);

  static int __init deferred_probe_timeout_setup(char *str)
  {

  	int timeout;
  
  	if (!kstrtoint(str, 10, &timeout))

  		driver_deferred_probe_timeout = timeout;

  	return 1;
  }
  __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
  
  /**
   * driver_deferred_probe_check_state() - Check deferred probe state
   * @dev: device to check
   *

   * Return:
   * -ENODEV if initcalls have completed and modules are disabled.
   * -ETIMEDOUT if the deferred probe timeout was set and has expired
   *  and modules are enabled.
   * -EPROBE_DEFER in other cases.

   *
   * Drivers or subsystems can opt-in to calling this function instead of directly
   * returning -EPROBE_DEFER.
   */
  int driver_deferred_probe_check_state(struct device *dev)
  {

  	if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {

  		dev_warn(dev, "ignoring dependency for device, assuming no driver
  ");

  		return -ENODEV;
  	}

  	if (!driver_deferred_probe_timeout && initcalls_done) {

  		dev_warn(dev, "deferred probe timeout, ignoring dependency
  ");

  		return -ETIMEDOUT;
  	}

  	return -EPROBE_DEFER;
  }
  
  static void deferred_probe_timeout_work_func(struct work_struct *work)
  {
  	struct device_private *private, *p;

  	driver_deferred_probe_timeout = 0;

  	driver_deferred_probe_trigger();
  	flush_work(&deferred_probe_work);
  
  	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)

  		dev_info(private->device, "deferred probe pending
  ");

  	wake_up_all(&probe_timeout_waitqueue);

  }
  static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);

  /**

   * deferred_probe_initcall() - Enable probing of deferred devices
   *
   * We don't want to get in the way when the bulk of drivers are getting probed.
   * Instead, this initcall makes sure that deferred probing is delayed until
   * late_initcall time.
   */
  static int deferred_probe_initcall(void)
  {

  	deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
  					       NULL, &deferred_devs_fops);

  	driver_deferred_probe_enable = true;
  	driver_deferred_probe_trigger();

  	/* Sort as many dependencies as possible before exiting initcalls */

  	flush_work(&deferred_probe_work);

  	initcalls_done = true;
  
  	/*
  	 * Trigger deferred probe again, this time we won't defer anything
  	 * that is optional
  	 */
  	driver_deferred_probe_trigger();
  	flush_work(&deferred_probe_work);

  	if (driver_deferred_probe_timeout > 0) {

  		schedule_delayed_work(&deferred_probe_timeout_work,

  			driver_deferred_probe_timeout * HZ);

  	}

  	return 0;
  }
  late_initcall(deferred_probe_initcall);

  static void __exit deferred_probe_exit(void)
  {
  	debugfs_remove_recursive(deferred_devices);
  }
  __exitcall(deferred_probe_exit);

  /**
   * device_is_bound() - Check if device is bound to a driver
   * @dev: device to check
   *
   * Returns true if passed device has already finished probing successfully
   * against a driver.
   *
   * This function must be called with the device lock held.
   */
  bool device_is_bound(struct device *dev)
  {

  	return dev->p && klist_node_attached(&dev->p->knode_driver);

  }

  static void driver_bound(struct device *dev)

  {

  	if (device_is_bound(dev)) {

  		pr_warn("%s: device %s already bound
  ",

  			__func__, kobject_name(&dev->kobj));

  		return;

  	}

  	pr_debug("driver: '%s': %s: bound to device '%s'
  ", dev->driver->name,
  		 __func__, dev_name(dev));

  	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);

  	device_links_driver_bound(dev);

  	device_pm_check_callbacks(dev);

  	/*

  	 * Force the device to the end of the dpm_list since
  	 * the PM code assumes that the order we add things to
  	 * the list is a good order for suspend but deferred
  	 * probe makes that very unsafe.
  	 */
  	device_pm_move_to_tail(dev);
  
  	/*

  	 * Make sure the device is no longer in one of the deferred lists and
  	 * kick off retrying all pending devices
  	 */

  	driver_deferred_probe_del(dev);
  	driver_deferred_probe_trigger();

  	if (dev->bus)

  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,

  					     BUS_NOTIFY_BOUND_DRIVER, dev);

  
  	kobject_uevent(&dev->kobj, KOBJ_BIND);

  }

  static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
  			    const char *buf, size_t count)
  {
  	device_lock(dev);

  	dev->driver->coredump(dev);

  	device_unlock(dev);
  
  	return count;
  }
  static DEVICE_ATTR_WO(coredump);

  static int driver_sysfs_add(struct device *dev)
  {
  	int ret;

  	if (dev->bus)
  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  					     BUS_NOTIFY_BIND_DRIVER, dev);

  	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,

  				kobject_name(&dev->kobj));
  	if (ret)
  		goto fail;
  
  	ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
  				"driver");
  	if (ret)
  		goto rm_dev;
  
  	if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
  	    !device_create_file(dev, &dev_attr_coredump))
  		return 0;
  
  	sysfs_remove_link(&dev->kobj, "driver");
  
  rm_dev:
  	sysfs_remove_link(&dev->driver->p->kobj,

  			  kobject_name(&dev->kobj));

  
  fail:

  	return ret;

  }

  static void driver_sysfs_remove(struct device *dev)
  {
  	struct device_driver *drv = dev->driver;
  
  	if (drv) {

  		if (drv->coredump)
  			device_remove_file(dev, &dev_attr_coredump);

  		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));

  		sysfs_remove_link(&dev->kobj, "driver");
  	}
  }
  
  /**

   * device_bind_driver - bind a driver to one device.
   * @dev: device.

   *

   * Allow manual attachment of a driver to a device.
   * Caller must have already set @dev->driver.

   *

   * Note that this does not modify the bus reference count.
   * Please verify that is accounted for before calling this.
   * (It is ok to call with no other effort from a driver's probe() method.)

   *

   * This function must be called with the device lock held.

   */
  int device_bind_driver(struct device *dev)
  {

  	int ret;
  
  	ret = driver_sysfs_add(dev);
  	if (!ret)
  		driver_bound(dev);

  	else if (dev->bus)
  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);

  	return ret;

  }

  EXPORT_SYMBOL_GPL(device_bind_driver);

  static atomic_t probe_count = ATOMIC_INIT(0);

  static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);

  static void driver_deferred_probe_add_trigger(struct device *dev,
  					      int local_trigger_count)
  {
  	driver_deferred_probe_add(dev);
  	/* Did a trigger occur while probing? Need to re-trigger if yes */
  	if (local_trigger_count != atomic_read(&deferred_trigger_count))
  		driver_deferred_probe_trigger();
  }

  static ssize_t state_synced_show(struct device *dev,
  				 struct device_attribute *attr, char *buf)
  {
  	bool val;
  
  	device_lock(dev);
  	val = dev->state_synced;
  	device_unlock(dev);

  	return sysfs_emit(buf, "%u
  ", val);

  }
  static DEVICE_ATTR_RO(state_synced);

  static int really_probe(struct device *dev, struct device_driver *drv)

  {

  	int ret = -EPROBE_DEFER;

  	int local_trigger_count = atomic_read(&deferred_trigger_count);

  	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
  			   !drv->suppress_bind_attrs;

  	if (defer_all_probes) {
  		/*
  		 * Value of defer_all_probes can be set only by

  		 * device_block_probing() which, in turn, will call

  		 * wait_for_device_probe() right after that to avoid any races.
  		 */
  		dev_dbg(dev, "Driver %s force probe deferral
  ", drv->name);
  		driver_deferred_probe_add(dev);
  		return ret;
  	}

  	ret = device_links_check_suppliers(dev);

  	if (ret == -EPROBE_DEFER)
  		driver_deferred_probe_add_trigger(dev, local_trigger_count);

  	if (ret)
  		return ret;

  	atomic_inc(&probe_count);

  	pr_debug("bus: '%s': %s: probing driver %s with device %s
  ",

  		 drv->bus->name, __func__, drv->name, dev_name(dev));

  	if (!list_empty(&dev->devres_head)) {
  		dev_crit(dev, "Resources present before probing
  ");

  		ret = -EBUSY;
  		goto done;

  	}

  re_probe:

  	dev->driver = drv;

  
  	/* If using pinctrl, bind pins now before probing */
  	ret = pinctrl_bind_pins(dev);
  	if (ret)

  		goto pinctrl_bind_failed;

  	if (dev->bus->dma_configure) {
  		ret = dev->bus->dma_configure(dev);
  		if (ret)

  			goto probe_failed;

  	}

  	if (driver_sysfs_add(dev)) {

  		pr_err("%s: driver_sysfs_add(%s) failed
  ",
  		       __func__, dev_name(dev));

  		goto probe_failed;
  	}

  	if (dev->pm_domain && dev->pm_domain->activate) {
  		ret = dev->pm_domain->activate(dev);
  		if (ret)
  			goto probe_failed;
  	}

  	if (dev->bus->probe) {
  		ret = dev->bus->probe(dev);

  		if (ret)

  			goto probe_failed;

  	} else if (drv->probe) {

  		ret = drv->probe(dev);

  		if (ret)

  			goto probe_failed;

  	}

  	if (device_add_groups(dev, drv->dev_groups)) {
  		dev_err(dev, "device_add_groups() failed
  ");
  		goto dev_groups_failed;
  	}

  	if (dev_has_sync_state(dev) &&
  	    device_create_file(dev, &dev_attr_state_synced)) {
  		dev_err(dev, "state_synced sysfs add failed
  ");
  		goto dev_sysfs_state_synced_failed;
  	}

  	if (test_remove) {
  		test_remove = false;

  		device_remove_file(dev, &dev_attr_state_synced);

  		device_remove_groups(dev, drv->dev_groups);

  		if (dev->bus->remove)

  			dev->bus->remove(dev);
  		else if (drv->remove)
  			drv->remove(dev);
  
  		devres_release_all(dev);
  		driver_sysfs_remove(dev);
  		dev->driver = NULL;
  		dev_set_drvdata(dev, NULL);
  		if (dev->pm_domain && dev->pm_domain->dismiss)
  			dev->pm_domain->dismiss(dev);
  		pm_runtime_reinit(dev);
  
  		goto re_probe;
  	}

  	pinctrl_init_done(dev);

  	if (dev->pm_domain && dev->pm_domain->sync)
  		dev->pm_domain->sync(dev);

  	driver_bound(dev);

  	ret = 1;

  	pr_debug("bus: '%s': %s: bound device %s to driver %s
  ",

  		 drv->bus->name, __func__, dev_name(dev), drv->name);

  	goto done;

  dev_sysfs_state_synced_failed:
  	device_remove_groups(dev, drv->dev_groups);

  dev_groups_failed:
  	if (dev->bus->remove)
  		dev->bus->remove(dev);
  	else if (drv->remove)
  		drv->remove(dev);

  probe_failed:

  	if (dev->bus)
  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
  pinctrl_bind_failed:

  	device_links_no_driver(dev);

  	devres_release_all(dev);

  	arch_teardown_dma_ops(dev);

  	driver_sysfs_remove(dev);
  	dev->driver = NULL;

  	dev_set_drvdata(dev, NULL);

  	if (dev->pm_domain && dev->pm_domain->dismiss)
  		dev->pm_domain->dismiss(dev);

  	pm_runtime_reinit(dev);

  	dev_pm_set_driver_flags(dev, 0);

  	switch (ret) {
  	case -EPROBE_DEFER:

  		/* Driver requested deferred probing */

  		dev_dbg(dev, "Driver %s requests probe deferral
  ", drv->name);

  		driver_deferred_probe_add_trigger(dev, local_trigger_count);

  		break;
  	case -ENODEV:
  	case -ENXIO:
  		pr_debug("%s: probe of %s rejects match %d
  ",
  			 drv->name, dev_name(dev), ret);
  		break;
  	default:

  		/* driver matched but the probe failed */

  		pr_warn("%s: probe of %s failed with error %d
  ",
  			drv->name, dev_name(dev), ret);

  	}

  	/*
  	 * Ignore errors returned by ->probe so that the next driver can try
  	 * its luck.
  	 */
  	ret = 0;

  done:

  	atomic_dec(&probe_count);

  	wake_up_all(&probe_waitqueue);

  	return ret;
  }

  /*
   * For initcall_debug, show the driver probe time.
   */
  static int really_probe_debug(struct device *dev, struct device_driver *drv)
  {

  	ktime_t calltime, rettime;

  	int ret;
  
  	calltime = ktime_get();
  	ret = really_probe(dev, drv);
  	rettime = ktime_get();

  	pr_debug("probe of %s returned %d after %lld usecs
  ",

  		 dev_name(dev), ret, ktime_us_delta(rettime, calltime));

  	return ret;
  }

  /**
   * driver_probe_done
   * Determine if the probe sequence is finished or not.
   *
   * Should somehow figure out how to use a semaphore, not an atomic variable...
   */
  int driver_probe_done(void)
  {

  	int local_probe_count = atomic_read(&probe_count);
  
  	pr_debug("%s: probe_count = %d
  ", __func__, local_probe_count);
  	if (local_probe_count)

  		return -EBUSY;
  	return 0;
  }
  
  /**

   * wait_for_device_probe
   * Wait for device probing to be completed.

   */

  void wait_for_device_probe(void)

  {

  	/* wait for probe timeout */
  	wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);

  	/* wait for the deferred probe workqueue to finish */

  	flush_work(&deferred_probe_work);

  	/* wait for the known devices to complete their probing */

  	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);

  	async_synchronize_full();

  }

  EXPORT_SYMBOL_GPL(wait_for_device_probe);

  
  /**

   * driver_probe_device - attempt to bind device & driver together
   * @drv: driver to bind a device to
   * @dev: device to try to bind to the driver
   *

   * This function returns -ENODEV if the device is not registered,

   * 1 if the device is bound successfully and 0 otherwise.

   *

   * This function must be called with @dev lock held.  When called for a
   * USB interface, @dev->parent lock must be held as well.

   *
   * If the device has a parent, runtime-resume the parent before driver probing.

   */

  int driver_probe_device(struct device_driver *drv, struct device *dev)

  {

  	int ret = 0;

  	if (!device_is_registered(dev))
  		return -ENODEV;

  	pr_debug("bus: '%s': %s: matched device %s with driver %s
  ",

  		 drv->bus->name, __func__, dev_name(dev), drv->name);

  	pm_runtime_get_suppliers(dev);

  	if (dev->parent)
  		pm_runtime_get_sync(dev->parent);

  	pm_runtime_barrier(dev);

  	if (initcall_debug)
  		ret = really_probe_debug(dev, drv);
  	else
  		ret = really_probe(dev, drv);

  	pm_request_idle(dev);

  	if (dev->parent)
  		pm_runtime_put(dev->parent);

  	pm_runtime_put_suppliers(dev);

  	return ret;

  }

  static inline bool cmdline_requested_async_probing(const char *drv_name)
  {
  	return parse_option_str(async_probe_drv_names, drv_name);
  }
  
  /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
  static int __init save_async_options(char *buf)
  {
  	if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)

  		pr_warn("Too long list of driver names for 'driver_async_probe'!
  ");

  
  	strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
  	return 0;
  }
  __setup("driver_async_probe=", save_async_options);

  bool driver_allows_async_probing(struct device_driver *drv)

  {

  	switch (drv->probe_type) {
  	case PROBE_PREFER_ASYNCHRONOUS:

  		return true;

  	case PROBE_FORCE_SYNCHRONOUS:
  		return false;
  
  	default:

  		if (cmdline_requested_async_probing(drv->name))
  			return true;

  		if (module_requested_async_probing(drv->owner))

  			return true;

  		return false;
  	}

  }
  
  struct device_attach_data {
  	struct device *dev;
  
  	/*
  	 * Indicates whether we are are considering asynchronous probing or
  	 * not. Only initial binding after device or driver registration
  	 * (including deferral processing) may be done asynchronously, the
  	 * rest is always synchronous, as we expect it is being done by
  	 * request from userspace.
  	 */
  	bool check_async;
  
  	/*
  	 * Indicates if we are binding synchronous or asynchronous drivers.
  	 * When asynchronous probing is enabled we'll execute 2 passes
  	 * over drivers: first pass doing synchronous probing and second
  	 * doing asynchronous probing (if synchronous did not succeed -
  	 * most likely because there was no driver requiring synchronous
  	 * probing - and we found asynchronous driver during first pass).
  	 * The 2 passes are done because we can't shoot asynchronous
  	 * probe for given device and driver from bus_for_each_drv() since
  	 * driver pointer is not guaranteed to stay valid once
  	 * bus_for_each_drv() iterates to the next driver on the bus.
  	 */
  	bool want_async;
  
  	/*
  	 * We'll set have_async to 'true' if, while scanning for matching
  	 * driver, we'll encounter one that requests asynchronous probing.
  	 */
  	bool have_async;
  };
  
  static int __device_attach_driver(struct device_driver *drv, void *_data)
  {
  	struct device_attach_data *data = _data;
  	struct device *dev = data->dev;
  	bool async_allowed;

  	int ret;

  	ret = driver_match_device(drv, dev);
  	if (ret == 0) {
  		/* no match */

  		return 0;

  	} else if (ret == -EPROBE_DEFER) {
  		dev_dbg(dev, "Device match requests probe deferral
  ");
  		driver_deferred_probe_add(dev);
  	} else if (ret < 0) {

  		dev_dbg(dev, "Bus failed to match device: %d
  ", ret);

  		return ret;
  	} /* ret > 0 means positive match */

  	async_allowed = driver_allows_async_probing(drv);
  
  	if (async_allowed)
  		data->have_async = true;
  
  	if (data->check_async && async_allowed != data->want_async)
  		return 0;

  	return driver_probe_device(drv, dev);

  }

  static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
  {
  	struct device *dev = _dev;
  	struct device_attach_data data = {
  		.dev		= dev,
  		.check_async	= true,
  		.want_async	= true,
  	};
  
  	device_lock(dev);

  	/*
  	 * Check if device has already been removed or claimed. This may
  	 * happen with driver loading, device discovery/registration,
  	 * and deferred probe processing happens all at once with
  	 * multiple threads.
  	 */
  	if (dev->p->dead || dev->driver)
  		goto out_unlock;

  	if (dev->parent)
  		pm_runtime_get_sync(dev->parent);

  	bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
  	dev_dbg(dev, "async probe completed
  ");
  
  	pm_request_idle(dev);

  	if (dev->parent)
  		pm_runtime_put(dev->parent);

  out_unlock:

  	device_unlock(dev);
  
  	put_device(dev);
  }

  static int __device_attach(struct device *dev, bool allow_async)

  {

  	int ret = 0;

  	device_lock(dev);

  	if (dev->p->dead) {
  		goto out_unlock;
  	} else if (dev->driver) {

  		if (device_is_bound(dev)) {

  			ret = 1;
  			goto out_unlock;
  		}

  		ret = device_bind_driver(dev);
  		if (ret == 0)
  			ret = 1;

  		else {
  			dev->driver = NULL;
  			ret = 0;
  		}

  	} else {

  		struct device_attach_data data = {
  			.dev = dev,
  			.check_async = allow_async,
  			.want_async = false,
  		};

  		if (dev->parent)
  			pm_runtime_get_sync(dev->parent);

  		ret = bus_for_each_drv(dev->bus, NULL, &data,
  					__device_attach_driver);
  		if (!ret && allow_async && data.have_async) {
  			/*
  			 * If we could not find appropriate driver
  			 * synchronously and we are allowed to do
  			 * async probes and there are drivers that
  			 * want to probe asynchronously, we'll
  			 * try them.
  			 */
  			dev_dbg(dev, "scheduling asynchronous probe
  ");
  			get_device(dev);

  			async_schedule_dev(__device_attach_async_helper, dev);

  		} else {
  			pm_request_idle(dev);
  		}

  
  		if (dev->parent)
  			pm_runtime_put(dev->parent);

  	}

  out_unlock:

  	device_unlock(dev);

  	return ret;

  }

  
  /**
   * device_attach - try to attach device to a driver.
   * @dev: device.
   *
   * Walk the list of drivers that the bus has and call
   * driver_probe_device() for each pair. If a compatible
   * pair is found, break out and return.
   *
   * Returns 1 if the device was bound to a driver;
   * 0 if no matching driver was found;
   * -ENODEV if the device is not registered.
   *
   * When called for a USB interface, @dev->parent lock must be held.
   */
  int device_attach(struct device *dev)
  {
  	return __device_attach(dev, false);
  }

  EXPORT_SYMBOL_GPL(device_attach);

  void device_initial_probe(struct device *dev)
  {
  	__device_attach(dev, true);
  }

  /*
   * __device_driver_lock - acquire locks needed to manipulate dev->drv
   * @dev: Device we will update driver info for
   * @parent: Parent device. Needed if the bus requires parent lock
   *
   * This function will take the required locks for manipulating dev->drv.
   * Normally this will just be the @dev lock, but when called for a USB
   * interface, @parent lock will be held as well.
   */
  static void __device_driver_lock(struct device *dev, struct device *parent)
  {
  	if (parent && dev->bus->need_parent_lock)
  		device_lock(parent);
  	device_lock(dev);
  }
  
  /*
   * __device_driver_unlock - release locks needed to manipulate dev->drv
   * @dev: Device we will update driver info for
   * @parent: Parent device. Needed if the bus requires parent lock
   *
   * This function will release the required locks for manipulating dev->drv.
   * Normally this will just be the the @dev lock, but when called for a
   * USB interface, @parent lock will be released as well.
   */
  static void __device_driver_unlock(struct device *dev, struct device *parent)
  {
  	device_unlock(dev);
  	if (parent && dev->bus->need_parent_lock)
  		device_unlock(parent);
  }
  
  /**
   * device_driver_attach - attach a specific driver to a specific device
   * @drv: Driver to attach
   * @dev: Device to attach it to
   *
   * Manually attach driver to a device. Will acquire both @dev lock and
   * @dev->parent lock if needed.
   */
  int device_driver_attach(struct device_driver *drv, struct device *dev)
  {
  	int ret = 0;
  
  	__device_driver_lock(dev, dev->parent);
  
  	/*
  	 * If device has been removed or someone has already successfully
  	 * bound a driver before us just skip the driver probe call.
  	 */
  	if (!dev->p->dead && !dev->driver)
  		ret = driver_probe_device(drv, dev);
  
  	__device_driver_unlock(dev, dev->parent);
  
  	return ret;
  }

  static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
  {
  	struct device *dev = _dev;
  	struct device_driver *drv;
  	int ret = 0;
  
  	__device_driver_lock(dev, dev->parent);
  
  	drv = dev->p->async_driver;
  
  	/*
  	 * If device has been removed or someone has already successfully
  	 * bound a driver before us just skip the driver probe call.
  	 */
  	if (!dev->p->dead && !dev->driver)
  		ret = driver_probe_device(drv, dev);
  
  	__device_driver_unlock(dev, dev->parent);
  
  	dev_dbg(dev, "driver %s async attach completed: %d
  ", drv->name, ret);
  
  	put_device(dev);
  }

  static int __driver_attach(struct device *dev, void *data)

  {

  	struct device_driver *drv = data;

  	int ret;

  
  	/*
  	 * Lock device and try to bind to it. We drop the error
  	 * here and always return 0, because we need to keep trying
  	 * to bind to devices and some drivers will return an error
  	 * simply if it didn't support the device.
  	 *
  	 * driver_probe_device() will spit a warning if there
  	 * is an error.
  	 */

  	ret = driver_match_device(drv, dev);
  	if (ret == 0) {
  		/* no match */

  		return 0;

  	} else if (ret == -EPROBE_DEFER) {
  		dev_dbg(dev, "Device match requests probe deferral
  ");
  		driver_deferred_probe_add(dev);
  	} else if (ret < 0) {

  		dev_dbg(dev, "Bus failed to match device: %d
  ", ret);

  		return ret;
  	} /* ret > 0 means positive match */

  	if (driver_allows_async_probing(drv)) {
  		/*
  		 * Instead of probing the device synchronously we will
  		 * probe it asynchronously to allow for more parallelism.
  		 *
  		 * We only take the device lock here in order to guarantee
  		 * that the dev->driver and async_driver fields are protected
  		 */
  		dev_dbg(dev, "probing driver %s asynchronously
  ", drv->name);
  		device_lock(dev);
  		if (!dev->driver) {
  			get_device(dev);
  			dev->p->async_driver = drv;

  			async_schedule_dev(__driver_attach_async_helper, dev);

  		}
  		device_unlock(dev);
  		return 0;
  	}

  	device_driver_attach(drv, dev);

  	return 0;
  }
  
  /**

   * driver_attach - try to bind driver to devices.
   * @drv: driver.

   *

   * Walk the list of devices that the bus has on it and try to
   * match the driver with each one.  If driver_probe_device()
   * returns 0 and the @dev->driver is set, we've found a
   * compatible pair.

   */

  int driver_attach(struct device_driver *drv)

  {

  	return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);

  }

  EXPORT_SYMBOL_GPL(driver_attach);

  /*

   * __device_release_driver() must be called with @dev lock held.
   * When called for a USB interface, @dev->parent lock must be held as well.

   */

  static void __device_release_driver(struct device *dev, struct device *parent)

  {

  	struct device_driver *drv;

  	drv = dev->driver;

  	if (drv) {

  		pm_runtime_get_sync(dev);

  		while (device_links_busy(dev)) {

  			__device_driver_unlock(dev, parent);

  
  			device_links_unbind_consumers(dev);

  			__device_driver_lock(dev, parent);

  			/*
  			 * A concurrent invocation of the same function might
  			 * have released the driver successfully while this one
  			 * was waiting, so check for that.
  			 */

  			if (dev->driver != drv) {
  				pm_runtime_put(dev);

  				return;

  			}

  		}

  		driver_sysfs_remove(dev);

  		if (dev->bus)

  			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,

  						     BUS_NOTIFY_UNBIND_DRIVER,
  						     dev);

  		pm_runtime_put_sync(dev);

  		device_remove_file(dev, &dev_attr_state_synced);

  		device_remove_groups(dev, drv->dev_groups);

  		if (dev->bus && dev->bus->remove)

  			dev->bus->remove(dev);
  		else if (drv->remove)

  			drv->remove(dev);

  
  		device_links_driver_cleanup(dev);

  		devres_release_all(dev);

  		arch_teardown_dma_ops(dev);

  		dev->driver = NULL;

  		dev_set_drvdata(dev, NULL);

  		if (dev->pm_domain && dev->pm_domain->dismiss)
  			dev->pm_domain->dismiss(dev);

  		pm_runtime_reinit(dev);

  		dev_pm_set_driver_flags(dev, 0);

  		klist_remove(&dev->p->knode_driver);

  		device_pm_check_callbacks(dev);

  		if (dev->bus)
  			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  						     BUS_NOTIFY_UNBOUND_DRIVER,
  						     dev);

  
  		kobject_uevent(&dev->kobj, KOBJ_UNBIND);

  	}

  }

  void device_release_driver_internal(struct device *dev,
  				    struct device_driver *drv,
  				    struct device *parent)

  {

  	__device_driver_lock(dev, parent);

  	if (!drv || drv == dev->driver)

  		__device_release_driver(dev, parent);

  	__device_driver_unlock(dev, parent);

  }

  /**

   * device_release_driver - manually detach device from driver.
   * @dev: device.

   *

   * Manually detach device from driver.

   * When called for a USB interface, @dev->parent lock must be held.

   *
   * If this function is to be called with @dev->parent lock held, ensure that
   * the device's consumers are unbound in advance or that their locks can be
   * acquired under the @dev->parent lock.

   */

  void device_release_driver(struct device *dev)

  {

  	/*
  	 * If anyone calls device_release_driver() recursively from
  	 * within their ->remove callback for the same device, they
  	 * will deadlock right here.
  	 */

  	device_release_driver_internal(dev, NULL, NULL);

  }

  EXPORT_SYMBOL_GPL(device_release_driver);

  /**

   * device_driver_detach - detach driver from a specific device
   * @dev: device to detach driver from
   *
   * Detach driver from device. Will acquire both @dev lock and @dev->parent
   * lock if needed.
   */
  void device_driver_detach(struct device *dev)
  {
  	device_release_driver_internal(dev, NULL, dev->parent);
  }
  
  /**

   * driver_detach - detach driver from all devices it controls.
   * @drv: driver.
   */

  void driver_detach(struct device_driver *drv)

  {

  	struct device_private *dev_prv;

  	struct device *dev;

  	if (driver_allows_async_probing(drv))
  		async_synchronize_full();

  	for (;;) {

  		spin_lock(&drv->p->klist_devices.k_lock);
  		if (list_empty(&drv->p->klist_devices.k_list)) {
  			spin_unlock(&drv->p->klist_devices.k_lock);

  			break;
  		}

  		dev_prv = list_last_entry(&drv->p->klist_devices.k_list,

  				     struct device_private,
  				     knode_driver.n_node);
  		dev = dev_prv->device;

  		get_device(dev);

  		spin_unlock(&drv->p->klist_devices.k_lock);

  		device_release_driver_internal(dev, drv, dev->parent);

  		put_device(dev);
  	}

  }