tty: Fix the ldisc hangup race

[linux-2.6/kvm.git] / drivers / base / dd.c

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


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);

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

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

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

        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 @dev->sem 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 (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;

        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);
        }
        /*
         * 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->sem held.  When called for a
 * USB interface, @dev->parent->sem 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_get_noresume(dev);
        pm_runtime_barrier(dev);
        ret = really_probe(dev, drv);
        pm_runtime_put_sync(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->sem must be held.
 */
int device_attach(struct device *dev)
{
        int ret = 0;

        down(&dev->sem);
        if (dev->driver) {
                ret = device_bind_driver(dev);
                if (ret == 0)
                        ret = 1;
                else {
                        dev->driver = NULL;
                        ret = 0;
                }
        } else {
                pm_runtime_get_noresume(dev);
                ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
                pm_runtime_put_sync(dev);
        }
        up(&dev->sem);
        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 */
                down(&dev->parent->sem);
        down(&dev->sem);
        if (!dev->driver)
                driver_probe_device(drv, dev);
        up(&dev->sem);
        if (dev->parent)
                up(&dev->parent->sem);

        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->sem held.
 * When called for a USB interface, @dev->parent->sem 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_noresume(dev);
                pm_runtime_barrier(dev);

                driver_sysfs_remove(dev);

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

                pm_runtime_put_sync(dev);
        }
}

/**
 * device_release_driver - manually detach device from driver.
 * @dev: device.
 *
 * Manually detach device from driver.
 * When called for a USB interface, @dev->parent->sem 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.
         */
        down(&dev->sem);
        __device_release_driver(dev);
        up(&dev->sem);
}
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 */
                        down(&dev->parent->sem);
                down(&dev->sem);
                if (dev->driver == drv)
                        __device_release_driver(dev);
                up(&dev->sem);
                if (dev->parent)
                        up(&dev->parent->sem);
                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);

void dev_set_drvdata(struct device *dev, void *data)
{
        int error;

        if (!dev)
                return;
        if (!dev->p) {
                error = device_private_init(dev);
                if (error)
                        return;
        }
        dev->p->driver_data = data;
}
EXPORT_SYMBOL(dev_set_drvdata);