[PATCH] Driver Core: fix bk-driver-core kills ppc64
There's no check to see if the device is already bound to a driver, which could do bad things. The first thing to go wrong is that it will try to match a driver with a device already bound to one. In some cases (it appears with USB with drivers/usb/core/usb.c::usb_match_id()), some drivers will match a device based on the class type, so it would be common (especially for HID devices) to match a device that is already bound. The fun comes when ->probe() is called, it fails, then driver_probe_device() does this: dev->driver = NULL; Later on, that pointer could be be dereferenced without checking and cause hell to break loose. This problem could be nasty. It's very hardware dependent, since some devices could have a different set of matching qualifiers than others. Now, I don't quite see exactly where/how you were getting that crash. You're dereferencing bad memory, but I'm not sure which pointer was bad and where it came from, but it could have come from a couple of different places. The patch below will hopefully fix it all up for you. It's against 2.6.12-rc2-mm1, and does the following: - Move logic to driver_probe_device() and comments uncommon returns: 1 - If device is bound 0 - If device not bound, and no error error - If there was an error. - Move locking to caller of that function, since we want to lock a device for the entire time we're trying to bind it to a driver (to prevent against a driver being loaded at the same time). - Update __device_attach() and __driver_attach() to do that locking. - Check if device is already bound in __driver_attach() - Update the converse device_release_driver() so it locks the device around all of the operations. - Mark driver_probe_device() as static and remove export. It's an internal function, it should stay that way, and there are no other callers. If there is ever a need to export it, we can audit it as necessary. Signed-off-by: Andrew Morton <akpm@osdl.org>
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@ -35,6 +35,8 @@
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* nor take the bus's rwsem. Please verify those are accounted
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* for before calling this. (It is ok to call with no other effort
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* from a driver's probe() method.)
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*
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* This function must be called with @dev->sem held.
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*/
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void device_bind_driver(struct device * dev)
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{
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@ -57,54 +59,56 @@ void device_bind_driver(struct device * dev)
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* because we don't know the format of the ID structures, nor what
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* is to be considered a match and what is not.
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*
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* If we find a match, we call @drv->probe(@dev) if it exists, and
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* call device_bind_driver() above.
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*
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* This function returns 1 if a match is found, an error if one
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* occurs (that is not -ENODEV or -ENXIO), and 0 otherwise.
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*
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* This function must be called with @dev->sem held.
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*/
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int driver_probe_device(struct device_driver * drv, struct device * dev)
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static int driver_probe_device(struct device_driver * drv, struct device * dev)
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{
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int error = 0;
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int ret = 0;
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if (drv->bus->match && !drv->bus->match(dev, drv))
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return -ENODEV;
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goto Done;
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down(&dev->sem);
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pr_debug("%s: Matched Device %s with Driver %s\n",
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drv->bus->name, dev->bus_id, drv->name);
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dev->driver = drv;
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if (drv->probe) {
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error = drv->probe(dev);
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if (error) {
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ret = drv->probe(dev);
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if (ret) {
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dev->driver = NULL;
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up(&dev->sem);
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return error;
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goto ProbeFailed;
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}
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}
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up(&dev->sem);
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device_bind_driver(dev);
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return 0;
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ret = 1;
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pr_debug("%s: Bound Device %s to Driver %s\n",
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drv->bus->name, dev->bus_id, drv->name);
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goto Done;
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ProbeFailed:
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if (ret == -ENODEV || ret == -ENXIO) {
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/* Driver matched, but didn't support device
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* or device not found.
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* Not an error; keep going.
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*/
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ret = 0;
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} else {
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/* driver matched but the probe failed */
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printk(KERN_WARNING
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"%s: probe of %s failed with error %d\n",
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drv->name, dev->bus_id, ret);
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}
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Done:
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return ret;
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}
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static int __device_attach(struct device_driver * drv, void * data)
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{
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struct device * dev = data;
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int error;
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error = driver_probe_device(drv, dev);
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if (error) {
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if ((error == -ENODEV) || (error == -ENXIO)) {
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/* Driver matched, but didn't support device
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* or device not found.
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* Not an error; keep going.
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*/
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error = 0;
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} else {
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/* driver matched but the probe failed */
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printk(KERN_WARNING
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"%s: probe of %s failed with error %d\n",
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drv->name, dev->bus_id, error);
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}
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return error;
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}
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/* stop looking, this device is attached */
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return 1;
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return driver_probe_device(drv, dev);
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}
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/**
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@ -114,37 +118,43 @@ static int __device_attach(struct device_driver * drv, void * data)
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* Walk the list of drivers that the bus has and call
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* driver_probe_device() for each pair. If a compatible
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* pair is found, break out and return.
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*
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* Returns 1 if the device was bound to a driver; 0 otherwise.
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*/
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int device_attach(struct device * dev)
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{
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int ret = 0;
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down(&dev->sem);
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if (dev->driver) {
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device_bind_driver(dev);
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return 1;
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}
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return bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
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ret = 1;
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} else
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ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
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up(&dev->sem);
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return ret;
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}
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static int __driver_attach(struct device * dev, void * data)
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{
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struct device_driver * drv = data;
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int error = 0;
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if (!dev->driver) {
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error = driver_probe_device(drv, dev);
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if (error) {
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if (error != -ENODEV) {
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/* driver matched but the probe failed */
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printk(KERN_WARNING
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"%s: probe of %s failed with error %d\n",
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drv->name, dev->bus_id, error);
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} else
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error = 0;
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return error;
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}
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/* stop looking, this driver is attached */
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return 1;
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}
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/*
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* Lock device and try to bind to it. We drop the error
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* here and always return 0, because we need to keep trying
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* to bind to devices and some drivers will return an error
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* simply if it didn't support the device.
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*
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* driver_probe_device() will spit a warning if there
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* is an error.
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*/
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down(&dev->sem);
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if (!dev->driver)
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driver_probe_device(drv, dev);
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up(&dev->sem);
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return 0;
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}
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@ -156,9 +166,6 @@ static int __driver_attach(struct device * dev, void * data)
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* match the driver with each one. If driver_probe_device()
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* returns 0 and the @dev->driver is set, we've found a
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* compatible pair.
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*
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* Note that we ignore the -ENODEV error from driver_probe_device(),
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* since it's perfectly valid for a driver not to bind to any devices.
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*/
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void driver_attach(struct device_driver * drv)
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{
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@ -176,19 +183,19 @@ void driver_attach(struct device_driver * drv)
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*/
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void device_release_driver(struct device * dev)
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{
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struct device_driver * drv = dev->driver;
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if (!drv)
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return;
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sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
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sysfs_remove_link(&dev->kobj, "driver");
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klist_del(&dev->knode_driver);
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struct device_driver * drv;
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down(&dev->sem);
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if (drv->remove)
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drv->remove(dev);
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dev->driver = NULL;
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if (dev->driver) {
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drv = dev->driver;
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sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
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sysfs_remove_link(&dev->kobj, "driver");
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klist_del(&dev->knode_driver);
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if (drv->remove)
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drv->remove(dev);
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dev->driver = NULL;
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}
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up(&dev->sem);
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}
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@ -208,7 +215,6 @@ void driver_detach(struct device_driver * drv)
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}
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EXPORT_SYMBOL_GPL(driver_probe_device);
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EXPORT_SYMBOL_GPL(device_bind_driver);
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EXPORT_SYMBOL_GPL(device_release_driver);
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EXPORT_SYMBOL_GPL(device_attach);
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@ -325,7 +325,6 @@ extern int device_for_each_child(struct device *, void *,
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* Manual binding of a device to driver. See drivers/base/bus.c
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* for information on use.
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*/
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extern int driver_probe_device(struct device_driver * drv, struct device * dev);
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extern void device_bind_driver(struct device * dev);
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extern void device_release_driver(struct device * dev);
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extern int device_attach(struct device * dev);
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