[PATCH] uml: watchdog driver locking

[linux-2.6/sactl.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
 *
 *      This file is released under the GPLv2
 */

#include <linux/device.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/wait.h>

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

#define to_drv(node) container_of(node, struct device_driver, kobj.entry)


static void driver_bound(struct device *dev)
{
        if (klist_node_attached(&dev->knode_driver)) {
                printk(KERN_WARNING "%s: device %s already bound\n",
                        __FUNCTION__, kobject_name(&dev->kobj));
                return;
        }

        pr_debug("bound device '%s' to driver '%s'\n",
                 dev->bus_id, dev->driver->name);

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

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

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

        ret = sysfs_create_link(&dev->driver->kobj, &dev->kobj,
                          kobject_name(&dev->kobj));
        if (ret == 0) {
                ret = sysfs_create_link(&dev->kobj, &dev->driver->kobj,
                                        "driver");
                if (ret)
                        sysfs_remove_link(&dev->driver->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->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;
}

struct stupid_thread_structure {
        struct device_driver *drv;
        struct device *dev;
};

static atomic_t probe_count = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);

static int really_probe(void *void_data)
{
        struct stupid_thread_structure *data = void_data;
        struct device_driver *drv = data->drv;
        struct device *dev = data->dev;
        int ret = 0;

        atomic_inc(&probe_count);
        pr_debug("%s: Probing driver %s with device %s\n",
                 drv->bus->name, drv->name, dev->bus_id);
        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",
                        __FUNCTION__, dev->bus_id);
                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("%s: Bound Device %s to Driver %s\n",
                 drv->bus->name, dev->bus_id, 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->bus_id, ret);
        }
        /*
         * Ignore errors returned by ->probe so that the next driver can try
         * its luck.
         */
        ret = 0;
done:
        kfree(data);
        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", __FUNCTION__,
                 atomic_read(&probe_count));
        if (atomic_read(&probe_count))
                return -EBUSY;
        return 0;
}

/**
 * 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
 *
 * First, we call the bus's match function, if one present, which should
 * compare the device IDs the driver supports with the device IDs of the
 * device. Note we don't do this ourselves because we don't know the
 * format of the ID structures, nor what is to be considered a match and
 * what is not.
 *
 * This function returns 1 if a match is found, an error if one occurs
 * (that is not -ENODEV or -ENXIO), 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)
{
        struct stupid_thread_structure *data;
        struct task_struct *probe_task;
        int ret = 0;

        if (!device_is_registered(dev))
                return -ENODEV;
        if (drv->bus->match && !drv->bus->match(dev, drv))
                goto done;

        pr_debug("%s: Matched Device %s with Driver %s\n",
                 drv->bus->name, dev->bus_id, drv->name);

        data = kmalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        data->drv = drv;
        data->dev = dev;

        if (drv->multithread_probe) {
                probe_task = kthread_run(really_probe, data,
                                         "probe-%s", dev->bus_id);
                if (IS_ERR(probe_task))
                        ret = really_probe(data);
        } else
                ret = really_probe(data);

done:
        return ret;
}

static int __device_attach(struct device_driver * drv, void * data)
{
        struct device * dev = data;
        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 device was found; error code otherwise.
 *
 *      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
                ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
        up(&dev->sem);
        return ret;
}

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 (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);
}

/**
 *      device_release_driver - manually detach device from driver.
 *      @dev:   device.
 *
 *      Manually detach device from driver.
 *
 *      __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) {
                get_driver(drv);
                driver_sysfs_remove(dev);
                sysfs_remove_link(&dev->kobj, "driver");
                klist_remove(&dev->knode_driver);

                if (dev->bus)
                        blocking_notifier_call_chain(&dev->bus->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;
                put_driver(drv);
        }
}

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);
}


/**
 * driver_detach - detach driver from all devices it controls.
 * @drv: driver.
 */
void driver_detach(struct device_driver * drv)
{
        struct device * dev;

        for (;;) {
                spin_lock(&drv->klist_devices.k_lock);
                if (list_empty(&drv->klist_devices.k_list)) {
                        spin_unlock(&drv->klist_devices.k_lock);
                        break;
                }
                dev = list_entry(drv->klist_devices.k_list.prev,
                                struct device, knode_driver.n_node);
                get_device(dev);
                spin_unlock(&drv->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);
        }
}

#ifdef CONFIG_PCI_MULTITHREAD_PROBE
static int __init wait_for_probes(void)
{
        DEFINE_WAIT(wait);

        printk(KERN_INFO "%s: waiting for %d threads\n", __FUNCTION__,
                        atomic_read(&probe_count));
        if (!atomic_read(&probe_count))
                return 0;
        while (atomic_read(&probe_count)) {
                prepare_to_wait(&probe_waitqueue, &wait, TASK_UNINTERRUPTIBLE);
                if (atomic_read(&probe_count))
                        schedule();
        }
        finish_wait(&probe_waitqueue, &wait);
        return 0;
}

core_initcall_sync(wait_for_probes);
postcore_initcall_sync(wait_for_probes);
arch_initcall_sync(wait_for_probes);
subsys_initcall_sync(wait_for_probes);
fs_initcall_sync(wait_for_probes);
device_initcall_sync(wait_for_probes);
late_initcall_sync(wait_for_probes);
#endif

EXPORT_SYMBOL_GPL(device_bind_driver);
EXPORT_SYMBOL_GPL(device_release_driver);
EXPORT_SYMBOL_GPL(device_attach);
EXPORT_SYMBOL_GPL(driver_attach);