Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 1180 insertions, 0 deletions

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
new file mode 100644
index 000000000..7ca47e5b3
--- /dev/null
+++ b/drivers/base/bus.c
@@ -0,0 +1,1180 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * bus.c - bus driver management
+ *
+ * Copyright (c) 2002-3 Patrick Mochel
+ * Copyright (c) 2002-3 Open Source Development Labs
+ * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (c) 2007 Novell Inc.
+ */
+
+#include <linux/async.h>
+#include <linux/device/bus.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+#include "base.h"
+#include "power/power.h"
+
+/* /sys/devices/system */
+static struct kset *system_kset;
+
+#define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
+
+/*
+ * sysfs bindings for drivers
+ */
+
+#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
+
+#define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
+	struct driver_attribute driver_attr_##_name =		\
+		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
+
+static int __must_check bus_rescan_devices_helper(struct device *dev,
+						void *data);
+
+static struct bus_type *bus_get(struct bus_type *bus)
+{
+	if (bus) {
+		kset_get(&bus->p->subsys);
+		return bus;
+	}
+	return NULL;
+}
+
+static void bus_put(struct bus_type *bus)
+{
+	if (bus)
+		kset_put(&bus->p->subsys);
+}
+
+static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
+			     char *buf)
+{
+	struct driver_attribute *drv_attr = to_drv_attr(attr);
+	struct driver_private *drv_priv = to_driver(kobj);
+	ssize_t ret = -EIO;
+
+	if (drv_attr->show)
+		ret = drv_attr->show(drv_priv->driver, buf);
+	return ret;
+}
+
+static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct driver_attribute *drv_attr = to_drv_attr(attr);
+	struct driver_private *drv_priv = to_driver(kobj);
+	ssize_t ret = -EIO;
+
+	if (drv_attr->store)
+		ret = drv_attr->store(drv_priv->driver, buf, count);
+	return ret;
+}
+
+static const struct sysfs_ops driver_sysfs_ops = {
+	.show	= drv_attr_show,
+	.store	= drv_attr_store,
+};
+
+static void driver_release(struct kobject *kobj)
+{
+	struct driver_private *drv_priv = to_driver(kobj);
+
+	pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
+	kfree(drv_priv);
+}
+
+static struct kobj_type driver_ktype = {
+	.sysfs_ops	= &driver_sysfs_ops,
+	.release	= driver_release,
+};
+
+/*
+ * sysfs bindings for buses
+ */
+static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
+			     char *buf)
+{
+	struct bus_attribute *bus_attr = to_bus_attr(attr);
+	struct subsys_private *subsys_priv = to_subsys_private(kobj);
+	ssize_t ret = 0;
+
+	if (bus_attr->show)
+		ret = bus_attr->show(subsys_priv->bus, buf);
+	return ret;
+}
+
+static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct bus_attribute *bus_attr = to_bus_attr(attr);
+	struct subsys_private *subsys_priv = to_subsys_private(kobj);
+	ssize_t ret = 0;
+
+	if (bus_attr->store)
+		ret = bus_attr->store(subsys_priv->bus, buf, count);
+	return ret;
+}
+
+static const struct sysfs_ops bus_sysfs_ops = {
+	.show	= bus_attr_show,
+	.store	= bus_attr_store,
+};
+
+int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
+{
+	int error;
+	if (bus_get(bus)) {
+		error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
+		bus_put(bus);
+	} else
+		error = -EINVAL;
+	return error;
+}
+EXPORT_SYMBOL_GPL(bus_create_file);
+
+void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
+{
+	if (bus_get(bus)) {
+		sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
+		bus_put(bus);
+	}
+}
+EXPORT_SYMBOL_GPL(bus_remove_file);
+
+static void bus_release(struct kobject *kobj)
+{
+	struct subsys_private *priv = to_subsys_private(kobj);
+	struct bus_type *bus = priv->bus;
+
+	kfree(priv);
+	bus->p = NULL;
+}
+
+static struct kobj_type bus_ktype = {
+	.sysfs_ops	= &bus_sysfs_ops,
+	.release	= bus_release,
+};
+
+static int bus_uevent_filter(struct kobject *kobj)
+{
+	const struct kobj_type *ktype = get_ktype(kobj);
+
+	if (ktype == &bus_ktype)
+		return 1;
+	return 0;
+}
+
+static const struct kset_uevent_ops bus_uevent_ops = {
+	.filter = bus_uevent_filter,
+};
+
+static struct kset *bus_kset;
+
+/* Manually detach a device from its associated driver. */
+static ssize_t unbind_store(struct device_driver *drv, const char *buf,
+			    size_t count)
+{
+	struct bus_type *bus = bus_get(drv->bus);
+	struct device *dev;
+	int err = -ENODEV;
+
+	dev = bus_find_device_by_name(bus, NULL, buf);
+	if (dev && dev->driver == drv) {
+		device_driver_detach(dev);
+		err = count;
+	}
+	put_device(dev);
+	bus_put(bus);
+	return err;
+}
+static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, 0200, NULL, unbind_store);
+
+/*
+ * Manually attach a device to a driver.
+ * Note: the driver must want to bind to the device,
+ * it is not possible to override the driver's id table.
+ */
+static ssize_t bind_store(struct device_driver *drv, const char *buf,
+			  size_t count)
+{
+	struct bus_type *bus = bus_get(drv->bus);
+	struct device *dev;
+	int err = -ENODEV;
+
+	dev = bus_find_device_by_name(bus, NULL, buf);
+	if (dev && driver_match_device(drv, dev)) {
+		err = device_driver_attach(drv, dev);
+		if (!err) {
+			/* success */
+			err = count;
+		}
+	}
+	put_device(dev);
+	bus_put(bus);
+	return err;
+}
+static DRIVER_ATTR_IGNORE_LOCKDEP(bind, 0200, NULL, bind_store);
+
+static ssize_t drivers_autoprobe_show(struct bus_type *bus, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", bus->p->drivers_autoprobe);
+}
+
+static ssize_t drivers_autoprobe_store(struct bus_type *bus,
+				       const char *buf, size_t count)
+{
+	if (buf[0] == '0')
+		bus->p->drivers_autoprobe = 0;
+	else
+		bus->p->drivers_autoprobe = 1;
+	return count;
+}
+
+static ssize_t drivers_probe_store(struct bus_type *bus,
+				   const char *buf, size_t count)
+{
+	struct device *dev;
+	int err = -EINVAL;
+
+	dev = bus_find_device_by_name(bus, NULL, buf);
+	if (!dev)
+		return -ENODEV;
+	if (bus_rescan_devices_helper(dev, NULL) == 0)
+		err = count;
+	put_device(dev);
+	return err;
+}
+
+static struct device *next_device(struct klist_iter *i)
+{
+	struct klist_node *n = klist_next(i);
+	struct device *dev = NULL;
+	struct device_private *dev_prv;
+
+	if (n) {
+		dev_prv = to_device_private_bus(n);
+		dev = dev_prv->device;
+	}
+	return dev;
+}
+
+/**
+ * bus_for_each_dev - device iterator.
+ * @bus: bus type.
+ * @start: device to start iterating from.
+ * @data: data for the callback.
+ * @fn: function to be called for each device.
+ *
+ * Iterate over @bus's list of devices, and call @fn for each,
+ * passing it @data. If @start is not NULL, we use that device to
+ * begin iterating from.
+ *
+ * We check the return of @fn each time. If it returns anything
+ * other than 0, we break out and return that value.
+ *
+ * NOTE: The device that returns a non-zero value is not retained
+ * in any way, nor is its refcount incremented. If the caller needs
+ * to retain this data, it should do so, and increment the reference
+ * count in the supplied callback.
+ */
+int bus_for_each_dev(struct bus_type *bus, struct device *start,
+		     void *data, int (*fn)(struct device *, void *))
+{
+	struct klist_iter i;
+	struct device *dev;
+	int error = 0;
+
+	if (!bus || !bus->p)
+		return -EINVAL;
+
+	klist_iter_init_node(&bus->p->klist_devices, &i,
+			     (start ? &start->p->knode_bus : NULL));
+	while (!error && (dev = next_device(&i)))
+		error = fn(dev, data);
+	klist_iter_exit(&i);
+	return error;
+}
+EXPORT_SYMBOL_GPL(bus_for_each_dev);
+
+/**
+ * bus_find_device - device iterator for locating a particular device.
+ * @bus: bus type
+ * @start: Device to begin with
+ * @data: Data to pass to match function
+ * @match: Callback function to check device
+ *
+ * This is similar to the bus_for_each_dev() function above, but it
+ * returns a reference to a device that is 'found' for later use, as
+ * determined by the @match callback.
+ *
+ * The callback should return 0 if the device doesn't match and non-zero
+ * if it does.  If the callback returns non-zero, this function will
+ * return to the caller and not iterate over any more devices.
+ */
+struct device *bus_find_device(struct bus_type *bus,
+			       struct device *start, const void *data,
+			       int (*match)(struct device *dev, const void *data))
+{
+	struct klist_iter i;
+	struct device *dev;
+
+	if (!bus || !bus->p)
+		return NULL;
+
+	klist_iter_init_node(&bus->p->klist_devices, &i,
+			     (start ? &start->p->knode_bus : NULL));
+	while ((dev = next_device(&i)))
+		if (match(dev, data) && get_device(dev))
+			break;
+	klist_iter_exit(&i);
+	return dev;
+}
+EXPORT_SYMBOL_GPL(bus_find_device);
+
+/**
+ * subsys_find_device_by_id - find a device with a specific enumeration number
+ * @subsys: subsystem
+ * @id: index 'id' in struct device
+ * @hint: device to check first
+ *
+ * Check the hint's next object and if it is a match return it directly,
+ * otherwise, fall back to a full list search. Either way a reference for
+ * the returned object is taken.
+ */
+struct device *subsys_find_device_by_id(struct bus_type *subsys, unsigned int id,
+					struct device *hint)
+{
+	struct klist_iter i;
+	struct device *dev;
+
+	if (!subsys)
+		return NULL;
+
+	if (hint) {
+		klist_iter_init_node(&subsys->p->klist_devices, &i, &hint->p->knode_bus);
+		dev = next_device(&i);
+		if (dev && dev->id == id && get_device(dev)) {
+			klist_iter_exit(&i);
+			return dev;
+		}
+		klist_iter_exit(&i);
+	}
+
+	klist_iter_init_node(&subsys->p->klist_devices, &i, NULL);
+	while ((dev = next_device(&i))) {
+		if (dev->id == id && get_device(dev)) {
+			klist_iter_exit(&i);
+			return dev;
+		}
+	}
+	klist_iter_exit(&i);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(subsys_find_device_by_id);
+
+static struct device_driver *next_driver(struct klist_iter *i)
+{
+	struct klist_node *n = klist_next(i);
+	struct driver_private *drv_priv;
+
+	if (n) {
+		drv_priv = container_of(n, struct driver_private, knode_bus);
+		return drv_priv->driver;
+	}
+	return NULL;
+}
+
+/**
+ * bus_for_each_drv - driver iterator
+ * @bus: bus we're dealing with.
+ * @start: driver to start iterating on.
+ * @data: data to pass to the callback.
+ * @fn: function to call for each driver.
+ *
+ * This is nearly identical to the device iterator above.
+ * We iterate over each driver that belongs to @bus, and call
+ * @fn for each. If @fn returns anything but 0, we break out
+ * and return it. If @start is not NULL, we use it as the head
+ * of the list.
+ *
+ * NOTE: we don't return the driver that returns a non-zero
+ * value, nor do we leave the reference count incremented for that
+ * driver. If the caller needs to know that info, it must set it
+ * in the callback. It must also be sure to increment the refcount
+ * so it doesn't disappear before returning to the caller.
+ */
+int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
+		     void *data, int (*fn)(struct device_driver *, void *))
+{
+	struct klist_iter i;
+	struct device_driver *drv;
+	int error = 0;
+
+	if (!bus)
+		return -EINVAL;
+
+	klist_iter_init_node(&bus->p->klist_drivers, &i,
+			     start ? &start->p->knode_bus : NULL);
+	while ((drv = next_driver(&i)) && !error)
+		error = fn(drv, data);
+	klist_iter_exit(&i);
+	return error;
+}
+EXPORT_SYMBOL_GPL(bus_for_each_drv);
+
+/**
+ * bus_add_device - add device to bus
+ * @dev: device being added
+ *
+ * - Add device's bus attributes.
+ * - Create links to device's bus.
+ * - Add the device to its bus's list of devices.
+ */
+int bus_add_device(struct device *dev)
+{
+	struct bus_type *bus = bus_get(dev->bus);
+	int error = 0;
+
+	if (bus) {
+		pr_debug("bus: '%s': add device %s\n", bus->name, dev_name(dev));
+		error = device_add_groups(dev, bus->dev_groups);
+		if (error)
+			goto out_put;
+		error = sysfs_create_link(&bus->p->devices_kset->kobj,
+						&dev->kobj, dev_name(dev));
+		if (error)
+			goto out_groups;
+		error = sysfs_create_link(&dev->kobj,
+				&dev->bus->p->subsys.kobj, "subsystem");
+		if (error)
+			goto out_subsys;
+		klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices);
+	}
+	return 0;
+
+out_subsys:
+	sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev));
+out_groups:
+	device_remove_groups(dev, bus->dev_groups);
+out_put:
+	bus_put(dev->bus);
+	return error;
+}
+
+/**
+ * bus_probe_device - probe drivers for a new device
+ * @dev: device to probe
+ *
+ * - Automatically probe for a driver if the bus allows it.
+ */
+void bus_probe_device(struct device *dev)
+{
+	struct bus_type *bus = dev->bus;
+	struct subsys_interface *sif;
+
+	if (!bus)
+		return;
+
+	if (bus->p->drivers_autoprobe)
+		device_initial_probe(dev);
+
+	mutex_lock(&bus->p->mutex);
+	list_for_each_entry(sif, &bus->p->interfaces, node)
+		if (sif->add_dev)
+			sif->add_dev(dev, sif);
+	mutex_unlock(&bus->p->mutex);
+}
+
+/**
+ * bus_remove_device - remove device from bus
+ * @dev: device to be removed
+ *
+ * - Remove device from all interfaces.
+ * - Remove symlink from bus' directory.
+ * - Delete device from bus's list.
+ * - Detach from its driver.
+ * - Drop reference taken in bus_add_device().
+ */
+void bus_remove_device(struct device *dev)
+{
+	struct bus_type *bus = dev->bus;
+	struct subsys_interface *sif;
+
+	if (!bus)
+		return;
+
+	mutex_lock(&bus->p->mutex);
+	list_for_each_entry(sif, &bus->p->interfaces, node)
+		if (sif->remove_dev)
+			sif->remove_dev(dev, sif);
+	mutex_unlock(&bus->p->mutex);
+
+	sysfs_remove_link(&dev->kobj, "subsystem");
+	sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
+			  dev_name(dev));
+	device_remove_groups(dev, dev->bus->dev_groups);
+	if (klist_node_attached(&dev->p->knode_bus))
+		klist_del(&dev->p->knode_bus);
+
+	pr_debug("bus: '%s': remove device %s\n",
+		 dev->bus->name, dev_name(dev));
+	device_release_driver(dev);
+	bus_put(dev->bus);
+}
+
+static int __must_check add_bind_files(struct device_driver *drv)
+{
+	int ret;
+
+	ret = driver_create_file(drv, &driver_attr_unbind);
+	if (ret == 0) {
+		ret = driver_create_file(drv, &driver_attr_bind);
+		if (ret)
+			driver_remove_file(drv, &driver_attr_unbind);
+	}
+	return ret;
+}
+
+static void remove_bind_files(struct device_driver *drv)
+{
+	driver_remove_file(drv, &driver_attr_bind);
+	driver_remove_file(drv, &driver_attr_unbind);
+}
+
+static BUS_ATTR_WO(drivers_probe);
+static BUS_ATTR_RW(drivers_autoprobe);
+
+static int add_probe_files(struct bus_type *bus)
+{
+	int retval;
+
+	retval = bus_create_file(bus, &bus_attr_drivers_probe);
+	if (retval)
+		goto out;
+
+	retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
+	if (retval)
+		bus_remove_file(bus, &bus_attr_drivers_probe);
+out:
+	return retval;
+}
+
+static void remove_probe_files(struct bus_type *bus)
+{
+	bus_remove_file(bus, &bus_attr_drivers_autoprobe);
+	bus_remove_file(bus, &bus_attr_drivers_probe);
+}
+
+static ssize_t uevent_store(struct device_driver *drv, const char *buf,
+			    size_t count)
+{
+	int rc;
+
+	rc = kobject_synth_uevent(&drv->p->kobj, buf, count);
+	return rc ? rc : count;
+}
+static DRIVER_ATTR_WO(uevent);
+
+/**
+ * bus_add_driver - Add a driver to the bus.
+ * @drv: driver.
+ */
+int bus_add_driver(struct device_driver *drv)
+{
+	struct bus_type *bus;
+	struct driver_private *priv;
+	int error = 0;
+
+	bus = bus_get(drv->bus);
+	if (!bus)
+		return -EINVAL;
+
+	pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv) {
+		error = -ENOMEM;
+		goto out_put_bus;
+	}
+	klist_init(&priv->klist_devices, NULL, NULL);
+	priv->driver = drv;
+	drv->p = priv;
+	priv->kobj.kset = bus->p->drivers_kset;
+	error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
+				     "%s", drv->name);
+	if (error)
+		goto out_unregister;
+
+	klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
+	if (drv->bus->p->drivers_autoprobe) {
+		error = driver_attach(drv);
+		if (error)
+			goto out_del_list;
+	}
+	module_add_driver(drv->owner, drv);
+
+	error = driver_create_file(drv, &driver_attr_uevent);
+	if (error) {
+		printk(KERN_ERR "%s: uevent attr (%s) failed\n",
+			__func__, drv->name);
+	}
+	error = driver_add_groups(drv, bus->drv_groups);
+	if (error) {
+		/* How the hell do we get out of this pickle? Give up */
+		printk(KERN_ERR "%s: driver_add_groups(%s) failed\n",
+			__func__, drv->name);
+	}
+
+	if (!drv->suppress_bind_attrs) {
+		error = add_bind_files(drv);
+		if (error) {
+			/* Ditto */
+			printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
+				__func__, drv->name);
+		}
+	}
+
+	return 0;
+
+out_del_list:
+	klist_del(&priv->knode_bus);
+out_unregister:
+	kobject_put(&priv->kobj);
+	/* drv->p is freed in driver_release()  */
+	drv->p = NULL;
+out_put_bus:
+	bus_put(bus);
+	return error;
+}
+
+/**
+ * bus_remove_driver - delete driver from bus's knowledge.
+ * @drv: driver.
+ *
+ * Detach the driver from the devices it controls, and remove
+ * it from its bus's list of drivers. Finally, we drop the reference
+ * to the bus we took in bus_add_driver().
+ */
+void bus_remove_driver(struct device_driver *drv)
+{
+	if (!drv->bus)
+		return;
+
+	if (!drv->suppress_bind_attrs)
+		remove_bind_files(drv);
+	driver_remove_groups(drv, drv->bus->drv_groups);
+	driver_remove_file(drv, &driver_attr_uevent);
+	klist_remove(&drv->p->knode_bus);
+	pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
+	driver_detach(drv);
+	module_remove_driver(drv);
+	kobject_put(&drv->p->kobj);
+	bus_put(drv->bus);
+}
+
+/* Helper for bus_rescan_devices's iter */
+static int __must_check bus_rescan_devices_helper(struct device *dev,
+						  void *data)
+{
+	int ret = 0;
+
+	if (!dev->driver) {
+		if (dev->parent && dev->bus->need_parent_lock)
+			device_lock(dev->parent);
+		ret = device_attach(dev);
+		if (dev->parent && dev->bus->need_parent_lock)
+			device_unlock(dev->parent);
+	}
+	return ret < 0 ? ret : 0;
+}
+
+/**
+ * bus_rescan_devices - rescan devices on the bus for possible drivers
+ * @bus: the bus to scan.
+ *
+ * This function will look for devices on the bus with no driver
+ * attached and rescan it against existing drivers to see if it matches
+ * any by calling device_attach() for the unbound devices.
+ */
+int bus_rescan_devices(struct bus_type *bus)
+{
+	return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
+}
+EXPORT_SYMBOL_GPL(bus_rescan_devices);
+
+/**
+ * device_reprobe - remove driver for a device and probe for a new driver
+ * @dev: the device to reprobe
+ *
+ * This function detaches the attached driver (if any) for the given
+ * device and restarts the driver probing process.  It is intended
+ * to use if probing criteria changed during a devices lifetime and
+ * driver attachment should change accordingly.
+ */
+int device_reprobe(struct device *dev)
+{
+	if (dev->driver)
+		device_driver_detach(dev);
+	return bus_rescan_devices_helper(dev, NULL);
+}
+EXPORT_SYMBOL_GPL(device_reprobe);
+
+static int bus_add_groups(struct bus_type *bus,
+			  const struct attribute_group **groups)
+{
+	return sysfs_create_groups(&bus->p->subsys.kobj, groups);
+}
+
+static void bus_remove_groups(struct bus_type *bus,
+			      const struct attribute_group **groups)
+{
+	sysfs_remove_groups(&bus->p->subsys.kobj, groups);
+}
+
+static void klist_devices_get(struct klist_node *n)
+{
+	struct device_private *dev_prv = to_device_private_bus(n);
+	struct device *dev = dev_prv->device;
+
+	get_device(dev);
+}
+
+static void klist_devices_put(struct klist_node *n)
+{
+	struct device_private *dev_prv = to_device_private_bus(n);
+	struct device *dev = dev_prv->device;
+
+	put_device(dev);
+}
+
+static ssize_t bus_uevent_store(struct bus_type *bus,
+				const char *buf, size_t count)
+{
+	int rc;
+
+	rc = kobject_synth_uevent(&bus->p->subsys.kobj, buf, count);
+	return rc ? rc : count;
+}
+/*
+ * "open code" the old BUS_ATTR() macro here.  We want to use BUS_ATTR_WO()
+ * here, but can not use it as earlier in the file we have
+ * DEVICE_ATTR_WO(uevent), which would cause a clash with the with the store
+ * function name.
+ */
+static struct bus_attribute bus_attr_uevent = __ATTR(uevent, 0200, NULL,
+						     bus_uevent_store);
+
+/**
+ * bus_register - register a driver-core subsystem
+ * @bus: bus to register
+ *
+ * Once we have that, we register the bus with the kobject
+ * infrastructure, then register the children subsystems it has:
+ * the devices and drivers that belong to the subsystem.
+ */
+int bus_register(struct bus_type *bus)
+{
+	int retval;
+	struct subsys_private *priv;
+	struct lock_class_key *key = &bus->lock_key;
+
+	priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->bus = bus;
+	bus->p = priv;
+
+	BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
+
+	retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
+	if (retval)
+		goto out;
+
+	priv->subsys.kobj.kset = bus_kset;
+	priv->subsys.kobj.ktype = &bus_ktype;
+	priv->drivers_autoprobe = 1;
+
+	retval = kset_register(&priv->subsys);
+	if (retval)
+		goto out;
+
+	retval = bus_create_file(bus, &bus_attr_uevent);
+	if (retval)
+		goto bus_uevent_fail;
+
+	priv->devices_kset = kset_create_and_add("devices", NULL,
+						 &priv->subsys.kobj);
+	if (!priv->devices_kset) {
+		retval = -ENOMEM;
+		goto bus_devices_fail;
+	}
+
+	priv->drivers_kset = kset_create_and_add("drivers", NULL,
+						 &priv->subsys.kobj);
+	if (!priv->drivers_kset) {
+		retval = -ENOMEM;
+		goto bus_drivers_fail;
+	}
+
+	INIT_LIST_HEAD(&priv->interfaces);
+	__mutex_init(&priv->mutex, "subsys mutex", key);
+	klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
+	klist_init(&priv->klist_drivers, NULL, NULL);
+
+	retval = add_probe_files(bus);
+	if (retval)
+		goto bus_probe_files_fail;
+
+	retval = bus_add_groups(bus, bus->bus_groups);
+	if (retval)
+		goto bus_groups_fail;
+
+	pr_debug("bus: '%s': registered\n", bus->name);
+	return 0;
+
+bus_groups_fail:
+	remove_probe_files(bus);
+bus_probe_files_fail:
+	kset_unregister(bus->p->drivers_kset);
+bus_drivers_fail:
+	kset_unregister(bus->p->devices_kset);
+bus_devices_fail:
+	bus_remove_file(bus, &bus_attr_uevent);
+bus_uevent_fail:
+	kset_unregister(&bus->p->subsys);
+out:
+	kfree(bus->p);
+	bus->p = NULL;
+	return retval;
+}
+EXPORT_SYMBOL_GPL(bus_register);
+
+/**
+ * bus_unregister - remove a bus from the system
+ * @bus: bus.
+ *
+ * Unregister the child subsystems and the bus itself.
+ * Finally, we call bus_put() to release the refcount
+ */
+void bus_unregister(struct bus_type *bus)
+{
+	pr_debug("bus: '%s': unregistering\n", bus->name);
+	if (bus->dev_root)
+		device_unregister(bus->dev_root);
+	bus_remove_groups(bus, bus->bus_groups);
+	remove_probe_files(bus);
+	kset_unregister(bus->p->drivers_kset);
+	kset_unregister(bus->p->devices_kset);
+	bus_remove_file(bus, &bus_attr_uevent);
+	kset_unregister(&bus->p->subsys);
+}
+EXPORT_SYMBOL_GPL(bus_unregister);
+
+int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(bus_register_notifier);
+
+int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(bus_unregister_notifier);
+
+struct kset *bus_get_kset(struct bus_type *bus)
+{
+	return &bus->p->subsys;
+}
+EXPORT_SYMBOL_GPL(bus_get_kset);
+
+struct klist *bus_get_device_klist(struct bus_type *bus)
+{
+	return &bus->p->klist_devices;
+}
+EXPORT_SYMBOL_GPL(bus_get_device_klist);
+
+/*
+ * Yes, this forcibly breaks the klist abstraction temporarily.  It
+ * just wants to sort the klist, not change reference counts and
+ * take/drop locks rapidly in the process.  It does all this while
+ * holding the lock for the list, so objects can't otherwise be
+ * added/removed while we're swizzling.
+ */
+static void device_insertion_sort_klist(struct device *a, struct list_head *list,
+					int (*compare)(const struct device *a,
+							const struct device *b))
+{
+	struct klist_node *n;
+	struct device_private *dev_prv;
+	struct device *b;
+
+	list_for_each_entry(n, list, n_node) {
+		dev_prv = to_device_private_bus(n);
+		b = dev_prv->device;
+		if (compare(a, b) <= 0) {
+			list_move_tail(&a->p->knode_bus.n_node,
+				       &b->p->knode_bus.n_node);
+			return;
+		}
+	}
+	list_move_tail(&a->p->knode_bus.n_node, list);
+}
+
+void bus_sort_breadthfirst(struct bus_type *bus,
+			   int (*compare)(const struct device *a,
+					  const struct device *b))
+{
+	LIST_HEAD(sorted_devices);
+	struct klist_node *n, *tmp;
+	struct device_private *dev_prv;
+	struct device *dev;
+	struct klist *device_klist;
+
+	device_klist = bus_get_device_klist(bus);
+
+	spin_lock(&device_klist->k_lock);
+	list_for_each_entry_safe(n, tmp, &device_klist->k_list, n_node) {
+		dev_prv = to_device_private_bus(n);
+		dev = dev_prv->device;
+		device_insertion_sort_klist(dev, &sorted_devices, compare);
+	}
+	list_splice(&sorted_devices, &device_klist->k_list);
+	spin_unlock(&device_klist->k_lock);
+}
+EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
+
+/**
+ * subsys_dev_iter_init - initialize subsys device iterator
+ * @iter: subsys iterator to initialize
+ * @subsys: the subsys we wanna iterate over
+ * @start: the device to start iterating from, if any
+ * @type: device_type of the devices to iterate over, NULL for all
+ *
+ * Initialize subsys iterator @iter such that it iterates over devices
+ * of @subsys.  If @start is set, the list iteration will start there,
+ * otherwise if it is NULL, the iteration starts at the beginning of
+ * the list.
+ */
+void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
+			  struct device *start, const struct device_type *type)
+{
+	struct klist_node *start_knode = NULL;
+
+	if (start)
+		start_knode = &start->p->knode_bus;
+	klist_iter_init_node(&subsys->p->klist_devices, &iter->ki, start_knode);
+	iter->type = type;
+}
+EXPORT_SYMBOL_GPL(subsys_dev_iter_init);
+
+/**
+ * subsys_dev_iter_next - iterate to the next device
+ * @iter: subsys iterator to proceed
+ *
+ * Proceed @iter to the next device and return it.  Returns NULL if
+ * iteration is complete.
+ *
+ * The returned device is referenced and won't be released till
+ * iterator is proceed to the next device or exited.  The caller is
+ * free to do whatever it wants to do with the device including
+ * calling back into subsys code.
+ */
+struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
+{
+	struct klist_node *knode;
+	struct device *dev;
+
+	for (;;) {
+		knode = klist_next(&iter->ki);
+		if (!knode)
+			return NULL;
+		dev = to_device_private_bus(knode)->device;
+		if (!iter->type || iter->type == dev->type)
+			return dev;
+	}
+}
+EXPORT_SYMBOL_GPL(subsys_dev_iter_next);
+
+/**
+ * subsys_dev_iter_exit - finish iteration
+ * @iter: subsys iterator to finish
+ *
+ * Finish an iteration.  Always call this function after iteration is
+ * complete whether the iteration ran till the end or not.
+ */
+void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
+{
+	klist_iter_exit(&iter->ki);
+}
+EXPORT_SYMBOL_GPL(subsys_dev_iter_exit);
+
+int subsys_interface_register(struct subsys_interface *sif)
+{
+	struct bus_type *subsys;
+	struct subsys_dev_iter iter;
+	struct device *dev;
+
+	if (!sif || !sif->subsys)
+		return -ENODEV;
+
+	subsys = bus_get(sif->subsys);
+	if (!subsys)
+		return -EINVAL;
+
+	mutex_lock(&subsys->p->mutex);
+	list_add_tail(&sif->node, &subsys->p->interfaces);
+	if (sif->add_dev) {
+		subsys_dev_iter_init(&iter, subsys, NULL, NULL);
+		while ((dev = subsys_dev_iter_next(&iter)))
+			sif->add_dev(dev, sif);
+		subsys_dev_iter_exit(&iter);
+	}
+	mutex_unlock(&subsys->p->mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(subsys_interface_register);
+
+void subsys_interface_unregister(struct subsys_interface *sif)
+{
+	struct bus_type *subsys;
+	struct subsys_dev_iter iter;
+	struct device *dev;
+
+	if (!sif || !sif->subsys)
+		return;
+
+	subsys = sif->subsys;
+
+	mutex_lock(&subsys->p->mutex);
+	list_del_init(&sif->node);
+	if (sif->remove_dev) {
+		subsys_dev_iter_init(&iter, subsys, NULL, NULL);
+		while ((dev = subsys_dev_iter_next(&iter)))
+			sif->remove_dev(dev, sif);
+		subsys_dev_iter_exit(&iter);
+	}
+	mutex_unlock(&subsys->p->mutex);
+
+	bus_put(subsys);
+}
+EXPORT_SYMBOL_GPL(subsys_interface_unregister);
+
+static void system_root_device_release(struct device *dev)
+{
+	kfree(dev);
+}
+
+static int subsys_register(struct bus_type *subsys,
+			   const struct attribute_group **groups,
+			   struct kobject *parent_of_root)
+{
+	struct device *dev;
+	int err;
+
+	err = bus_register(subsys);
+	if (err < 0)
+		return err;
+
+	dev = kzalloc(sizeof(struct device), GFP_KERNEL);
+	if (!dev) {
+		err = -ENOMEM;
+		goto err_dev;
+	}
+
+	err = dev_set_name(dev, "%s", subsys->name);
+	if (err < 0)
+		goto err_name;
+
+	dev->kobj.parent = parent_of_root;
+	dev->groups = groups;
+	dev->release = system_root_device_release;
+
+	err = device_register(dev);
+	if (err < 0)
+		goto err_dev_reg;
+
+	subsys->dev_root = dev;
+	return 0;
+
+err_dev_reg:
+	put_device(dev);
+	dev = NULL;
+err_name:
+	kfree(dev);
+err_dev:
+	bus_unregister(subsys);
+	return err;
+}
+
+/**
+ * subsys_system_register - register a subsystem at /sys/devices/system/
+ * @subsys: system subsystem
+ * @groups: default attributes for the root device
+ *
+ * All 'system' subsystems have a /sys/devices/system/<name> root device
+ * with the name of the subsystem. The root device can carry subsystem-
+ * wide attributes. All registered devices are below this single root
+ * device and are named after the subsystem with a simple enumeration
+ * number appended. The registered devices are not explicitly named;
+ * only 'id' in the device needs to be set.
+ *
+ * Do not use this interface for anything new, it exists for compatibility
+ * with bad ideas only. New subsystems should use plain subsystems; and
+ * add the subsystem-wide attributes should be added to the subsystem
+ * directory itself and not some create fake root-device placed in
+ * /sys/devices/system/<name>.
+ */
+int subsys_system_register(struct bus_type *subsys,
+			   const struct attribute_group **groups)
+{
+	return subsys_register(subsys, groups, &system_kset->kobj);
+}
+EXPORT_SYMBOL_GPL(subsys_system_register);
+
+/**
+ * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
+ * @subsys: virtual subsystem
+ * @groups: default attributes for the root device
+ *
+ * All 'virtual' subsystems have a /sys/devices/system/<name> root device
+ * with the name of the subystem.  The root device can carry subsystem-wide
+ * attributes.  All registered devices are below this single root device.
+ * There's no restriction on device naming.  This is for kernel software
+ * constructs which need sysfs interface.
+ */
+int subsys_virtual_register(struct bus_type *subsys,
+			    const struct attribute_group **groups)
+{
+	struct kobject *virtual_dir;
+
+	virtual_dir = virtual_device_parent(NULL);
+	if (!virtual_dir)
+		return -ENOMEM;
+
+	return subsys_register(subsys, groups, virtual_dir);
+}
+EXPORT_SYMBOL_GPL(subsys_virtual_register);
+
+int __init buses_init(void)
+{
+	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
+	if (!bus_kset)
+		return -ENOMEM;
+
+	system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);
+	if (!system_kset)
+		return -ENOMEM;
+
+	return 0;
+}