text: /*
   * 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.
   *
   * This file is released under the GPLv2
   */
  
  #include <linux/device.h>
  #include <linux/delay.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 "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 struct workqueue_struct *deferred_wq;
  
  /**
   * 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);
  
  		/*
  		 * 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_lock();
  		device_pm_move_last(dev);
  		device_pm_unlock();
  
  		dev_dbg(dev, "Retrying from deferred list\n");
  		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);
  
  static 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\n");
  		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\n");
  		list_del_init(&dev->p->deferred_probe);
  	}
  	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.
   */
  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);
  	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.
  	 */
  	queue_work(deferred_wq, &deferred_probe_work);
  }
  
  /**
   * 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_wq = create_singlethread_workqueue("deferwq");
  	if (WARN_ON(!deferred_wq))
  		return -ENOMEM;
  
  	driver_deferred_probe_enable = true;
  	driver_deferred_probe_trigger();
  	/* Sort as many dependencies as possible before exiting initcalls */
  	flush_workqueue(deferred_wq);
  	return 0;
  }
  late_initcall(deferred_probe_initcall);
  
  static void driver_bound(struct device *dev)
  {
  	if (klist_node_attached(&dev->p->knode_driver)) {
  		printk(KERN_WARNING "%s: device %s already bound\n",
  			__func__, kobject_name(&dev->kobj));
  		return;
  	}
  
  	pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
  		 __func__, dev->driver->name);
  
  	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
  
  	/*
  	 * 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);
  }
  
  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 == 0) {
  		ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
  					"driver");
  		if (ret)
  			sysfs_remove_link(&dev->driver->p->kobj,
  					kobject_name(&dev->kobj));
  	}
  	return ret;
  }
  
  static void driver_sysfs_remove(struct device *dev)
  {
  	struct device_driver *drv = dev->driver;
  
  	if (drv) {
  		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
   * nor take the bus's rwsem. Please verify those are 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);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(device_bind_driver);
  
  static atomic_t probe_count = ATOMIC_INIT(0);
  static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
  
  static int really_probe(struct device *dev, struct device_driver *drv)
  {
  	int ret = 0;
  
  	atomic_inc(&probe_count);
  	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
  		 drv->bus->name, __func__, drv->name, dev_name(dev));
  	WARN_ON(!list_empty(&dev->devres_head));
  
  	dev->driver = drv;
  
  	/* If using pinctrl, bind pins now before probing */
  	ret = pinctrl_bind_pins(dev);
  	if (ret)
  		goto probe_failed;
  
  	if (driver_sysfs_add(dev)) {
  		printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
  			__func__, dev_name(dev));
  		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;
  	}
  
  	driver_bound(dev);
  	ret = 1;
  	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
  		 drv->bus->name, __func__, dev_name(dev), drv->name);
  	goto done;
  
  probe_failed:
  	devres_release_all(dev);
  	driver_sysfs_remove(dev);
  	dev->driver = NULL;
  	dev_set_drvdata(dev, NULL);
  
  	if (ret == -EPROBE_DEFER) {
  		/* Driver requested deferred probing */
  		dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
  		driver_deferred_probe_add(dev);
  	} else if (ret != -ENODEV && ret != -ENXIO) {
  		/* driver matched but the probe failed */
  		printk(KERN_WARNING
  		       "%s: probe of %s failed with error %d\n",
  		       drv->name, dev_name(dev), ret);
  	} else {
  		pr_debug("%s: probe of %s rejects match %d\n",
  		       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(&probe_waitqueue);
  	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)
  {
  	pr_debug("%s: probe_count = %d\n", __func__,
  		 atomic_read(&probe_count));
  	if (atomic_read(&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 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.
   */
  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\n",
  		 drv->bus->name, __func__, dev_name(dev), drv->name);
  
  	pm_runtime_barrier(dev);
  	ret = really_probe(dev, drv);
  	pm_request_idle(dev);
  
  	return ret;
  }
  
  static int __device_attach(struct device_driver *drv, void *data)
  {
  	struct device *dev = data;
  
  	if (!driver_match_device(drv, dev))
  		return 0;
  
  	return driver_probe_device(drv, dev);
  }
  
  /**
   * 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)
  {
  	int ret = 0;
  
  	device_lock(dev);
  	if (dev->driver) {
  		if (klist_node_attached(&dev->p->knode_driver)) {
  			ret = 1;
  			goto out_unlock;
  		}
  		ret = device_bind_driver(dev);
  		if (ret == 0)
  			ret = 1;
  		else {
  			dev->driver = NULL;
  			ret = 0;
  		}
  	} else {
  		ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
  		pm_request_idle(dev);
  	}
  out_unlock:
  	device_unlock(dev);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(device_attach);
  
  static int __driver_attach(struct device *dev, void *data)
  {
  	struct device_driver *drv = data;
  
  	/*
  	 * 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.
  	 */
  
  	if (!driver_match_device(drv, dev))
  		return 0;
  
  	if (dev->parent)	/* Needed for USB */
  		device_lock(dev->parent);
  	device_lock(dev);
  	if (!dev->driver)
  		driver_probe_device(drv, dev);
  	device_unlock(dev);
  	if (dev->parent)
  		device_unlock(dev->parent);
  
  	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_driver *drv;
  
  	drv = dev->driver;
  	if (drv) {
  		pm_runtime_get_sync(dev);
  
  		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);
  
  		if (dev->bus && dev->bus->remove)
  			dev->bus->remove(dev);
  		else if (drv->remove)
  			drv->remove(dev);
  		devres_release_all(dev);
  		dev->driver = NULL;
  		dev_set_drvdata(dev, NULL);
  		klist_remove(&dev->p->knode_driver);
  		if (dev->bus)
  			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  						     BUS_NOTIFY_UNBOUND_DRIVER,
  						     dev);
  
  	}
  }
  
  /**
   * 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.
   */
  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_lock(dev);
  	__device_release_driver(dev);
  	device_unlock(dev);
  }
  EXPORT_SYMBOL_GPL(device_release_driver);
  
  /**
   * 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;
  
  	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_entry(drv->p->klist_devices.k_list.prev,
  				     struct device_private,
  				     knode_driver.n_node);
  		dev = dev_prv->device;
  		get_device(dev);
  		spin_unlock(&drv->p->klist_devices.k_lock);
  
  		if (dev->parent)	/* Needed for USB */
  			device_lock(dev->parent);
  		device_lock(dev);
  		if (dev->driver == drv)
  			__device_release_driver(dev);
  		device_unlock(dev);
  		if (dev->parent)
  			device_unlock(dev->parent);
  		put_device(dev);
  	}
  }
  
  /*
   * These exports can't be _GPL due to .h files using this within them, and it
   * might break something that was previously working...
   */
  void *dev_get_drvdata(const struct device *dev)
  {
  	if (dev && dev->p)
  		return dev->p->driver_data;
  	return NULL;
  }
  EXPORT_SYMBOL(dev_get_drvdata);
  
  int dev_set_drvdata(struct device *dev, void *data)
  {
  	int error;
  
  	if (!dev->p) {
  		error = device_private_init(dev);
  		if (error)
  			return error;
  	}
  	dev->p->driver_data = data;
  	return 0;
  }
  EXPORT_SYMBOL(dev_set_drvdata);
  