2 * drivers/base/dd.c - The core device/driver interactions.
4 * This file contains the (sometimes tricky) code that controls the
5 * interactions between devices and drivers, which primarily includes
6 * driver binding and unbinding.
8 * All of this code used to exist in drivers/base/bus.c, but was
9 * relocated to here in the name of compartmentalization (since it wasn't
10 * strictly code just for the 'struct bus_type'.
12 * Copyright (c) 2002-5 Patrick Mochel
13 * Copyright (c) 2002-3 Open Source Development Labs
14 * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
15 * Copyright (c) 2007-2009 Novell Inc.
17 * This file is released under the GPLv2
20 #include <linux/device.h>
21 #include <linux/delay.h>
22 #include <linux/module.h>
23 #include <linux/kthread.h>
24 #include <linux/wait.h>
25 #include <linux/async.h>
26 #include <linux/pm_runtime.h>
29 #include "power/power.h"
32 * Deferred Probe infrastructure.
34 * Sometimes driver probe order matters, but the kernel doesn't always have
35 * dependency information which means some drivers will get probed before a
36 * resource it depends on is available. For example, an SDHCI driver may
37 * first need a GPIO line from an i2c GPIO controller before it can be
38 * initialized. If a required resource is not available yet, a driver can
39 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
41 * Deferred probe maintains two lists of devices, a pending list and an active
42 * list. A driver returning -EPROBE_DEFER causes the device to be added to the
43 * pending list. A successful driver probe will trigger moving all devices
44 * from the pending to the active list so that the workqueue will eventually
47 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
48 * of the (struct device*)->deferred_probe pointers are manipulated
50 static DEFINE_MUTEX(deferred_probe_mutex);
51 static LIST_HEAD(deferred_probe_pending_list);
52 static LIST_HEAD(deferred_probe_active_list);
53 static struct workqueue_struct *deferred_wq;
56 * deferred_probe_work_func() - Retry probing devices in the active list.
58 static void deferred_probe_work_func(struct work_struct *work)
62 * This block processes every device in the deferred 'active' list.
63 * Each device is removed from the active list and passed to
64 * bus_probe_device() to re-attempt the probe. The loop continues
65 * until every device in the active list is removed and retried.
67 * Note: Once the device is removed from the list and the mutex is
68 * released, it is possible for the device get freed by another thread
69 * and cause a illegal pointer dereference. This code uses
70 * get/put_device() to ensure the device structure cannot disappear
71 * from under our feet.
73 mutex_lock(&deferred_probe_mutex);
74 while (!list_empty(&deferred_probe_active_list)) {
75 dev = list_first_entry(&deferred_probe_active_list,
76 typeof(*dev), deferred_probe);
77 list_del_init(&dev->deferred_probe);
81 /* Drop the mutex while probing each device; the probe path
82 * may manipulate the deferred list */
83 mutex_unlock(&deferred_probe_mutex);
84 dev_dbg(dev, "Retrying from deferred list\n");
85 bus_probe_device(dev);
86 mutex_lock(&deferred_probe_mutex);
90 mutex_unlock(&deferred_probe_mutex);
92 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
94 static void driver_deferred_probe_add(struct device *dev)
96 mutex_lock(&deferred_probe_mutex);
97 if (list_empty(&dev->deferred_probe)) {
98 dev_dbg(dev, "Added to deferred list\n");
99 list_add(&dev->deferred_probe, &deferred_probe_pending_list);
101 mutex_unlock(&deferred_probe_mutex);
104 void driver_deferred_probe_del(struct device *dev)
106 mutex_lock(&deferred_probe_mutex);
107 if (!list_empty(&dev->deferred_probe)) {
108 dev_dbg(dev, "Removed from deferred list\n");
109 list_del_init(&dev->deferred_probe);
111 mutex_unlock(&deferred_probe_mutex);
114 static bool driver_deferred_probe_enable = false;
116 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
118 * This functions moves all devices from the pending list to the active
119 * list and schedules the deferred probe workqueue to process them. It
120 * should be called anytime a driver is successfully bound to a device.
122 static void driver_deferred_probe_trigger(void)
124 if (!driver_deferred_probe_enable)
127 /* A successful probe means that all the devices in the pending list
128 * should be triggered to be reprobed. Move all the deferred devices
129 * into the active list so they can be retried by the workqueue */
130 mutex_lock(&deferred_probe_mutex);
131 list_splice_tail_init(&deferred_probe_pending_list,
132 &deferred_probe_active_list);
133 mutex_unlock(&deferred_probe_mutex);
135 /* Kick the re-probe thread. It may already be scheduled, but
136 * it is safe to kick it again. */
137 queue_work(deferred_wq, &deferred_probe_work);
141 * deferred_probe_initcall() - Enable probing of deferred devices
143 * We don't want to get in the way when the bulk of drivers are getting probed.
144 * Instead, this initcall makes sure that deferred probing is delayed until
145 * late_initcall time.
147 static int deferred_probe_initcall(void)
149 deferred_wq = create_singlethread_workqueue("deferwq");
150 if (WARN_ON(!deferred_wq))
153 driver_deferred_probe_enable = true;
154 driver_deferred_probe_trigger();
157 late_initcall(deferred_probe_initcall);
159 static void driver_bound(struct device *dev)
161 if (klist_node_attached(&dev->p->knode_driver)) {
162 printk(KERN_WARNING "%s: device %s already bound\n",
163 __func__, kobject_name(&dev->kobj));
167 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
168 __func__, dev->driver->name);
170 klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
172 /* Make sure the device is no longer in one of the deferred lists
173 * and kick off retrying all pending devices */
174 driver_deferred_probe_del(dev);
175 driver_deferred_probe_trigger();
178 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
179 BUS_NOTIFY_BOUND_DRIVER, dev);
182 static int driver_sysfs_add(struct device *dev)
187 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
188 BUS_NOTIFY_BIND_DRIVER, dev);
190 ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
191 kobject_name(&dev->kobj));
193 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
196 sysfs_remove_link(&dev->driver->p->kobj,
197 kobject_name(&dev->kobj));
202 static void driver_sysfs_remove(struct device *dev)
204 struct device_driver *drv = dev->driver;
207 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
208 sysfs_remove_link(&dev->kobj, "driver");
213 * device_bind_driver - bind a driver to one device.
216 * Allow manual attachment of a driver to a device.
217 * Caller must have already set @dev->driver.
219 * Note that this does not modify the bus reference count
220 * nor take the bus's rwsem. Please verify those are accounted
221 * for before calling this. (It is ok to call with no other effort
222 * from a driver's probe() method.)
224 * This function must be called with the device lock held.
226 int device_bind_driver(struct device *dev)
230 ret = driver_sysfs_add(dev);
235 EXPORT_SYMBOL_GPL(device_bind_driver);
237 static atomic_t probe_count = ATOMIC_INIT(0);
238 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
240 static int really_probe(struct device *dev, struct device_driver *drv)
244 atomic_inc(&probe_count);
245 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
246 drv->bus->name, __func__, drv->name, dev_name(dev));
247 WARN_ON(!list_empty(&dev->devres_head));
250 if (driver_sysfs_add(dev)) {
251 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
252 __func__, dev_name(dev));
256 if (dev->bus->probe) {
257 ret = dev->bus->probe(dev);
260 } else if (drv->probe) {
261 ret = drv->probe(dev);
268 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
269 drv->bus->name, __func__, dev_name(dev), drv->name);
273 devres_release_all(dev);
274 driver_sysfs_remove(dev);
277 if (ret == -EPROBE_DEFER) {
278 /* Driver requested deferred probing */
279 dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
280 driver_deferred_probe_add(dev);
281 } else if (ret != -ENODEV && ret != -ENXIO) {
282 /* driver matched but the probe failed */
284 "%s: probe of %s failed with error %d\n",
285 drv->name, dev_name(dev), ret);
287 pr_debug("%s: probe of %s rejects match %d\n",
288 drv->name, dev_name(dev), ret);
291 * Ignore errors returned by ->probe so that the next driver can try
296 atomic_dec(&probe_count);
297 wake_up(&probe_waitqueue);
303 * Determine if the probe sequence is finished or not.
305 * Should somehow figure out how to use a semaphore, not an atomic variable...
307 int driver_probe_done(void)
309 pr_debug("%s: probe_count = %d\n", __func__,
310 atomic_read(&probe_count));
311 if (atomic_read(&probe_count))
317 * wait_for_device_probe
318 * Wait for device probing to be completed.
320 void wait_for_device_probe(void)
322 /* wait for the known devices to complete their probing */
323 wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
324 async_synchronize_full();
326 EXPORT_SYMBOL_GPL(wait_for_device_probe);
329 * driver_probe_device - attempt to bind device & driver together
330 * @drv: driver to bind a device to
331 * @dev: device to try to bind to the driver
333 * This function returns -ENODEV if the device is not registered,
334 * 1 if the device is bound successfully and 0 otherwise.
336 * This function must be called with @dev lock held. When called for a
337 * USB interface, @dev->parent lock must be held as well.
339 int driver_probe_device(struct device_driver *drv, struct device *dev)
343 if (!device_is_registered(dev))
346 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
347 drv->bus->name, __func__, dev_name(dev), drv->name);
349 pm_runtime_get_noresume(dev);
350 pm_runtime_barrier(dev);
351 ret = really_probe(dev, drv);
352 pm_runtime_put_sync(dev);
357 static int __device_attach(struct device_driver *drv, void *data)
359 struct device *dev = data;
361 if (!driver_match_device(drv, dev))
364 return driver_probe_device(drv, dev);
368 * device_attach - try to attach device to a driver.
371 * Walk the list of drivers that the bus has and call
372 * driver_probe_device() for each pair. If a compatible
373 * pair is found, break out and return.
375 * Returns 1 if the device was bound to a driver;
376 * 0 if no matching driver was found;
377 * -ENODEV if the device is not registered.
379 * When called for a USB interface, @dev->parent lock must be held.
381 int device_attach(struct device *dev)
387 if (klist_node_attached(&dev->p->knode_driver)) {
391 ret = device_bind_driver(dev);
399 pm_runtime_get_noresume(dev);
400 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
401 pm_runtime_put_sync(dev);
407 EXPORT_SYMBOL_GPL(device_attach);
409 static int __driver_attach(struct device *dev, void *data)
411 struct device_driver *drv = data;
414 * Lock device and try to bind to it. We drop the error
415 * here and always return 0, because we need to keep trying
416 * to bind to devices and some drivers will return an error
417 * simply if it didn't support the device.
419 * driver_probe_device() will spit a warning if there
423 if (!driver_match_device(drv, dev))
426 if (dev->parent) /* Needed for USB */
427 device_lock(dev->parent);
430 driver_probe_device(drv, dev);
433 device_unlock(dev->parent);
439 * driver_attach - try to bind driver to devices.
442 * Walk the list of devices that the bus has on it and try to
443 * match the driver with each one. If driver_probe_device()
444 * returns 0 and the @dev->driver is set, we've found a
447 int driver_attach(struct device_driver *drv)
449 return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
451 EXPORT_SYMBOL_GPL(driver_attach);
454 * __device_release_driver() must be called with @dev lock held.
455 * When called for a USB interface, @dev->parent lock must be held as well.
457 static void __device_release_driver(struct device *dev)
459 struct device_driver *drv;
463 pm_runtime_get_sync(dev);
465 driver_sysfs_remove(dev);
468 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
469 BUS_NOTIFY_UNBIND_DRIVER,
472 pm_runtime_put_sync(dev);
474 if (dev->bus && dev->bus->remove)
475 dev->bus->remove(dev);
476 else if (drv->remove)
478 devres_release_all(dev);
480 klist_remove(&dev->p->knode_driver);
482 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
483 BUS_NOTIFY_UNBOUND_DRIVER,
490 * device_release_driver - manually detach device from driver.
493 * Manually detach device from driver.
494 * When called for a USB interface, @dev->parent lock must be held.
496 void device_release_driver(struct device *dev)
499 * If anyone calls device_release_driver() recursively from
500 * within their ->remove callback for the same device, they
501 * will deadlock right here.
504 __device_release_driver(dev);
507 EXPORT_SYMBOL_GPL(device_release_driver);
510 * driver_detach - detach driver from all devices it controls.
513 void driver_detach(struct device_driver *drv)
515 struct device_private *dev_prv;
519 spin_lock(&drv->p->klist_devices.k_lock);
520 if (list_empty(&drv->p->klist_devices.k_list)) {
521 spin_unlock(&drv->p->klist_devices.k_lock);
524 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
525 struct device_private,
526 knode_driver.n_node);
527 dev = dev_prv->device;
529 spin_unlock(&drv->p->klist_devices.k_lock);
531 if (dev->parent) /* Needed for USB */
532 device_lock(dev->parent);
534 if (dev->driver == drv)
535 __device_release_driver(dev);
538 device_unlock(dev->parent);
544 * These exports can't be _GPL due to .h files using this within them, and it
545 * might break something that was previously working...
547 void *dev_get_drvdata(const struct device *dev)
550 return dev->p->driver_data;
553 EXPORT_SYMBOL(dev_get_drvdata);
555 int dev_set_drvdata(struct device *dev, void *data)
560 error = device_private_init(dev);
564 dev->p->driver_data = data;
567 EXPORT_SYMBOL(dev_set_drvdata);