Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1062 insertions, 0 deletions

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
new file mode 100644
index 000000000..26ba7a99b
--- /dev/null
+++ b/drivers/base/dd.c
@@ -0,0 +1,1062 @@
+// 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-mapping.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 "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;
+
+/*
+ * 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);
+
+		/*
+		 * 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);
+
+		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);
+
+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.
+ *
+ * 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/defere 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();
+}
+
+/*
+ * 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\n", dev_name(curr->device));
+
+	mutex_unlock(&deferred_probe_mutex);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(deferred_devs);
+
+static int deferred_probe_timeout = -1;
+static int __init deferred_probe_timeout_setup(char *str)
+{
+	deferred_probe_timeout = simple_strtol(str, NULL, 10);
+	return 1;
+}
+__setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
+
+/**
+ * driver_deferred_probe_check_state() - Check deferred probe state
+ * @dev: device to check
+ *
+ * Returns -ENODEV if init is done and all built-in drivers have had a chance
+ * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
+ * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
+ *
+ * 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 (initcalls_done) {
+		if (!deferred_probe_timeout) {
+			dev_WARN(dev, "deferred probe timeout, ignoring dependency");
+			return -ETIMEDOUT;
+		}
+		dev_warn(dev, "ignoring dependency for device, assuming no driver");
+		return -ENODEV;
+	}
+	return -EPROBE_DEFER;
+}
+
+static void deferred_probe_timeout_work_func(struct work_struct *work)
+{
+	struct device_private *p;
+
+	deferred_probe_timeout = 0;
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	mutex_lock(&deferred_probe_mutex);
+	list_for_each_entry(p, &deferred_probe_pending_list, deferred_probe)
+		dev_info(p->device, "deferred probe pending\n");
+	mutex_unlock(&deferred_probe_mutex);
+}
+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 (deferred_probe_timeout > 0) {
+		schedule_delayed_work(&deferred_probe_timeout_work,
+			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)) {
+		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->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);
+
+	/*
+	 * 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
+ * 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);
+	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 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_defer_all_probes_enable() which, in turn, will call
+		 * wait_for_device_probe() right after that to avoid any races.
+		 */
+		dev_dbg(dev, "Driver %s force probe deferral\n", 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\n",
+		 drv->bus->name, __func__, drv->name, dev_name(dev));
+	if (!list_empty(&dev->devres_head)) {
+		dev_crit(dev, "Resources present before probing\n");
+		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;
+
+	ret = dma_configure(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->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 (test_remove) {
+		test_remove = false;
+
+		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\n",
+		 drv->bus->name, __func__, dev_name(dev), drv->name);
+	goto done;
+
+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);
+	dma_deconfigure(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\n", 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\n",
+			 drv->name, dev_name(dev), ret);
+		break;
+	default:
+		/* driver matched but the probe failed */
+		printk(KERN_WARNING
+		       "%s: probe of %s failed with error %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_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, delta, rettime;
+	int ret;
+
+	calltime = ktime_get();
+	ret = really_probe(dev, drv);
+	rettime = ktime_get();
+	delta = ktime_sub(rettime, calltime);
+	printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
+	       dev_name(dev), ret, (s64) ktime_to_us(delta));
+	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 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\n",
+		 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;
+}
+
+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 (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\n");
+		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\n");
+
+	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\n");
+			get_device(dev);
+			async_schedule(__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);
+}
+
+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\n");
+		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 (dev->parent && dev->bus->need_parent_lock)
+		device_lock(dev->parent);
+	device_lock(dev);
+	if (!dev->p->dead && !dev->driver)
+		driver_probe_device(drv, dev);
+	device_unlock(dev);
+	if (dev->parent && dev->bus->need_parent_lock)
+		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 *parent)
+{
+	struct device_driver *drv;
+
+	drv = dev->driver;
+	if (drv) {
+		pm_runtime_get_sync(dev);
+
+		while (device_links_busy(dev)) {
+			device_unlock(dev);
+			if (parent && dev->bus->need_parent_lock)
+				device_unlock(parent);
+
+			device_links_unbind_consumers(dev);
+			if (parent && dev->bus->need_parent_lock)
+				device_lock(parent);
+
+			device_lock(dev);
+			/*
+			 * 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;
+			}
+		}
+
+		pm_runtime_clean_up_links(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);
+
+		device_links_driver_cleanup(dev);
+
+		devres_release_all(dev);
+		dma_deconfigure(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)
+{
+	if (parent && dev->bus->need_parent_lock)
+		device_lock(parent);
+
+	device_lock(dev);
+	if (!drv || drv == dev->driver)
+		__device_release_driver(dev, parent);
+
+	device_unlock(dev);
+	if (parent && dev->bus->need_parent_lock)
+		device_unlock(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);
+
+/**
+ * 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_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);
+		device_release_driver_internal(dev, drv, dev->parent);
+		put_device(dev);
+	}
+}