Root/drivers/base/dd.c

1/*
2 * drivers/base/dd.c - The core device/driver interactions.
3 *
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.
7 *
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'.
11 *
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.
16 *
17 * This file is released under the GPLv2
18 */
19
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>
27
28#include "base.h"
29#include "power/power.h"
30
31/*
32 * Deferred Probe infrastructure.
33 *
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
40 *
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
45 * retry them.
46 *
47 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
48 * of the (struct device*)->p->deferred_probe pointers are manipulated
49 */
50static DEFINE_MUTEX(deferred_probe_mutex);
51static LIST_HEAD(deferred_probe_pending_list);
52static LIST_HEAD(deferred_probe_active_list);
53static struct workqueue_struct *deferred_wq;
54
55/**
56 * deferred_probe_work_func() - Retry probing devices in the active list.
57 */
58static void deferred_probe_work_func(struct work_struct *work)
59{
60    struct device *dev;
61    struct device_private *private;
62    /*
63     * This block processes every device in the deferred 'active' list.
64     * Each device is removed from the active list and passed to
65     * bus_probe_device() to re-attempt the probe. The loop continues
66     * until every device in the active list is removed and retried.
67     *
68     * Note: Once the device is removed from the list and the mutex is
69     * released, it is possible for the device get freed by another thread
70     * and cause a illegal pointer dereference. This code uses
71     * get/put_device() to ensure the device structure cannot disappear
72     * from under our feet.
73     */
74    mutex_lock(&deferred_probe_mutex);
75    while (!list_empty(&deferred_probe_active_list)) {
76        private = list_first_entry(&deferred_probe_active_list,
77                    typeof(*dev->p), deferred_probe);
78        dev = private->device;
79        list_del_init(&private->deferred_probe);
80
81        get_device(dev);
82
83        /*
84         * Drop the mutex while probing each device; the probe path may
85         * manipulate the deferred list
86         */
87        mutex_unlock(&deferred_probe_mutex);
88
89        /*
90         * Force the device to the end of the dpm_list since
91         * the PM code assumes that the order we add things to
92         * the list is a good order for suspend but deferred
93         * probe makes that very unsafe.
94         */
95        device_pm_lock();
96        device_pm_move_last(dev);
97        device_pm_unlock();
98
99        dev_dbg(dev, "Retrying from deferred list\n");
100        bus_probe_device(dev);
101
102        mutex_lock(&deferred_probe_mutex);
103
104        put_device(dev);
105    }
106    mutex_unlock(&deferred_probe_mutex);
107}
108static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
109
110static void driver_deferred_probe_add(struct device *dev)
111{
112    mutex_lock(&deferred_probe_mutex);
113    if (list_empty(&dev->p->deferred_probe)) {
114        dev_dbg(dev, "Added to deferred list\n");
115        list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
116    }
117    mutex_unlock(&deferred_probe_mutex);
118}
119
120void driver_deferred_probe_del(struct device *dev)
121{
122    mutex_lock(&deferred_probe_mutex);
123    if (!list_empty(&dev->p->deferred_probe)) {
124        dev_dbg(dev, "Removed from deferred list\n");
125        list_del_init(&dev->p->deferred_probe);
126    }
127    mutex_unlock(&deferred_probe_mutex);
128}
129
130static bool driver_deferred_probe_enable = false;
131/**
132 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
133 *
134 * This functions moves all devices from the pending list to the active
135 * list and schedules the deferred probe workqueue to process them. It
136 * should be called anytime a driver is successfully bound to a device.
137 */
138static void driver_deferred_probe_trigger(void)
139{
140    if (!driver_deferred_probe_enable)
141        return;
142
143    /*
144     * A successful probe means that all the devices in the pending list
145     * should be triggered to be reprobed. Move all the deferred devices
146     * into the active list so they can be retried by the workqueue
147     */
148    mutex_lock(&deferred_probe_mutex);
149    list_splice_tail_init(&deferred_probe_pending_list,
150                  &deferred_probe_active_list);
151    mutex_unlock(&deferred_probe_mutex);
152
153    /*
154     * Kick the re-probe thread. It may already be scheduled, but it is
155     * safe to kick it again.
156     */
157    queue_work(deferred_wq, &deferred_probe_work);
158}
159
160/**
161 * deferred_probe_initcall() - Enable probing of deferred devices
162 *
163 * We don't want to get in the way when the bulk of drivers are getting probed.
164 * Instead, this initcall makes sure that deferred probing is delayed until
165 * late_initcall time.
166 */
167static int deferred_probe_initcall(void)
168{
169    deferred_wq = create_singlethread_workqueue("deferwq");
170    if (WARN_ON(!deferred_wq))
171        return -ENOMEM;
172
173    driver_deferred_probe_enable = true;
174    driver_deferred_probe_trigger();
175    return 0;
176}
177late_initcall(deferred_probe_initcall);
178
179static void driver_bound(struct device *dev)
180{
181    if (klist_node_attached(&dev->p->knode_driver)) {
182        printk(KERN_WARNING "%s: device %s already bound\n",
183            __func__, kobject_name(&dev->kobj));
184        return;
185    }
186
187    pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
188         __func__, dev->driver->name);
189
190    klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
191
192    /*
193     * Make sure the device is no longer in one of the deferred lists and
194     * kick off retrying all pending devices
195     */
196    driver_deferred_probe_del(dev);
197    driver_deferred_probe_trigger();
198
199    if (dev->bus)
200        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
201                         BUS_NOTIFY_BOUND_DRIVER, dev);
202}
203
204static int driver_sysfs_add(struct device *dev)
205{
206    int ret;
207
208    if (dev->bus)
209        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
210                         BUS_NOTIFY_BIND_DRIVER, dev);
211
212    ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
213              kobject_name(&dev->kobj));
214    if (ret == 0) {
215        ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
216                    "driver");
217        if (ret)
218            sysfs_remove_link(&dev->driver->p->kobj,
219                    kobject_name(&dev->kobj));
220    }
221    return ret;
222}
223
224static void driver_sysfs_remove(struct device *dev)
225{
226    struct device_driver *drv = dev->driver;
227
228    if (drv) {
229        sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
230        sysfs_remove_link(&dev->kobj, "driver");
231    }
232}
233
234/**
235 * device_bind_driver - bind a driver to one device.
236 * @dev: device.
237 *
238 * Allow manual attachment of a driver to a device.
239 * Caller must have already set @dev->driver.
240 *
241 * Note that this does not modify the bus reference count
242 * nor take the bus's rwsem. Please verify those are accounted
243 * for before calling this. (It is ok to call with no other effort
244 * from a driver's probe() method.)
245 *
246 * This function must be called with the device lock held.
247 */
248int device_bind_driver(struct device *dev)
249{
250    int ret;
251
252    ret = driver_sysfs_add(dev);
253    if (!ret)
254        driver_bound(dev);
255    return ret;
256}
257EXPORT_SYMBOL_GPL(device_bind_driver);
258
259static atomic_t probe_count = ATOMIC_INIT(0);
260static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
261
262static int really_probe(struct device *dev, struct device_driver *drv)
263{
264    int ret = 0;
265
266    atomic_inc(&probe_count);
267    pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
268         drv->bus->name, __func__, drv->name, dev_name(dev));
269    WARN_ON(!list_empty(&dev->devres_head));
270
271    dev->driver = drv;
272    if (driver_sysfs_add(dev)) {
273        printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
274            __func__, dev_name(dev));
275        goto probe_failed;
276    }
277
278    if (dev->bus->probe) {
279        ret = dev->bus->probe(dev);
280        if (ret)
281            goto probe_failed;
282    } else if (drv->probe) {
283        ret = drv->probe(dev);
284        if (ret)
285            goto probe_failed;
286    }
287
288    driver_bound(dev);
289    ret = 1;
290    pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
291         drv->bus->name, __func__, dev_name(dev), drv->name);
292    goto done;
293
294probe_failed:
295    devres_release_all(dev);
296    driver_sysfs_remove(dev);
297    dev->driver = NULL;
298    dev_set_drvdata(dev, NULL);
299
300    if (ret == -EPROBE_DEFER) {
301        /* Driver requested deferred probing */
302        dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
303        driver_deferred_probe_add(dev);
304    } else if (ret != -ENODEV && ret != -ENXIO) {
305        /* driver matched but the probe failed */
306        printk(KERN_WARNING
307               "%s: probe of %s failed with error %d\n",
308               drv->name, dev_name(dev), ret);
309    } else {
310        pr_debug("%s: probe of %s rejects match %d\n",
311               drv->name, dev_name(dev), ret);
312    }
313    /*
314     * Ignore errors returned by ->probe so that the next driver can try
315     * its luck.
316     */
317    ret = 0;
318done:
319    atomic_dec(&probe_count);
320    wake_up(&probe_waitqueue);
321    return ret;
322}
323
324/**
325 * driver_probe_done
326 * Determine if the probe sequence is finished or not.
327 *
328 * Should somehow figure out how to use a semaphore, not an atomic variable...
329 */
330int driver_probe_done(void)
331{
332    pr_debug("%s: probe_count = %d\n", __func__,
333         atomic_read(&probe_count));
334    if (atomic_read(&probe_count))
335        return -EBUSY;
336    return 0;
337}
338
339/**
340 * wait_for_device_probe
341 * Wait for device probing to be completed.
342 */
343void wait_for_device_probe(void)
344{
345    /* wait for the known devices to complete their probing */
346    wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
347    async_synchronize_full();
348}
349EXPORT_SYMBOL_GPL(wait_for_device_probe);
350
351/**
352 * driver_probe_device - attempt to bind device & driver together
353 * @drv: driver to bind a device to
354 * @dev: device to try to bind to the driver
355 *
356 * This function returns -ENODEV if the device is not registered,
357 * 1 if the device is bound successfully and 0 otherwise.
358 *
359 * This function must be called with @dev lock held. When called for a
360 * USB interface, @dev->parent lock must be held as well.
361 */
362int driver_probe_device(struct device_driver *drv, struct device *dev)
363{
364    int ret = 0;
365
366    if (!device_is_registered(dev))
367        return -ENODEV;
368
369    pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
370         drv->bus->name, __func__, dev_name(dev), drv->name);
371
372    pm_runtime_barrier(dev);
373    ret = really_probe(dev, drv);
374    pm_runtime_idle(dev);
375
376    return ret;
377}
378
379static int __device_attach(struct device_driver *drv, void *data)
380{
381    struct device *dev = data;
382
383    if (!driver_match_device(drv, dev))
384        return 0;
385
386    return driver_probe_device(drv, dev);
387}
388
389/**
390 * device_attach - try to attach device to a driver.
391 * @dev: device.
392 *
393 * Walk the list of drivers that the bus has and call
394 * driver_probe_device() for each pair. If a compatible
395 * pair is found, break out and return.
396 *
397 * Returns 1 if the device was bound to a driver;
398 * 0 if no matching driver was found;
399 * -ENODEV if the device is not registered.
400 *
401 * When called for a USB interface, @dev->parent lock must be held.
402 */
403int device_attach(struct device *dev)
404{
405    int ret = 0;
406
407    device_lock(dev);
408    if (dev->driver) {
409        if (klist_node_attached(&dev->p->knode_driver)) {
410            ret = 1;
411            goto out_unlock;
412        }
413        ret = device_bind_driver(dev);
414        if (ret == 0)
415            ret = 1;
416        else {
417            dev->driver = NULL;
418            ret = 0;
419        }
420    } else {
421        ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
422        pm_runtime_idle(dev);
423    }
424out_unlock:
425    device_unlock(dev);
426    return ret;
427}
428EXPORT_SYMBOL_GPL(device_attach);
429
430static int __driver_attach(struct device *dev, void *data)
431{
432    struct device_driver *drv = data;
433
434    /*
435     * Lock device and try to bind to it. We drop the error
436     * here and always return 0, because we need to keep trying
437     * to bind to devices and some drivers will return an error
438     * simply if it didn't support the device.
439     *
440     * driver_probe_device() will spit a warning if there
441     * is an error.
442     */
443
444    if (!driver_match_device(drv, dev))
445        return 0;
446
447    if (dev->parent) /* Needed for USB */
448        device_lock(dev->parent);
449    device_lock(dev);
450    if (!dev->driver)
451        driver_probe_device(drv, dev);
452    device_unlock(dev);
453    if (dev->parent)
454        device_unlock(dev->parent);
455
456    return 0;
457}
458
459/**
460 * driver_attach - try to bind driver to devices.
461 * @drv: driver.
462 *
463 * Walk the list of devices that the bus has on it and try to
464 * match the driver with each one. If driver_probe_device()
465 * returns 0 and the @dev->driver is set, we've found a
466 * compatible pair.
467 */
468int driver_attach(struct device_driver *drv)
469{
470    return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
471}
472EXPORT_SYMBOL_GPL(driver_attach);
473
474/*
475 * __device_release_driver() must be called with @dev lock held.
476 * When called for a USB interface, @dev->parent lock must be held as well.
477 */
478static void __device_release_driver(struct device *dev)
479{
480    struct device_driver *drv;
481
482    drv = dev->driver;
483    if (drv) {
484        pm_runtime_get_sync(dev);
485
486        driver_sysfs_remove(dev);
487
488        if (dev->bus)
489            blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
490                             BUS_NOTIFY_UNBIND_DRIVER,
491                             dev);
492
493        pm_runtime_put_sync(dev);
494
495        if (dev->bus && dev->bus->remove)
496            dev->bus->remove(dev);
497        else if (drv->remove)
498            drv->remove(dev);
499        devres_release_all(dev);
500        dev->driver = NULL;
501        dev_set_drvdata(dev, NULL);
502        klist_remove(&dev->p->knode_driver);
503        if (dev->bus)
504            blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
505                             BUS_NOTIFY_UNBOUND_DRIVER,
506                             dev);
507
508    }
509}
510
511/**
512 * device_release_driver - manually detach device from driver.
513 * @dev: device.
514 *
515 * Manually detach device from driver.
516 * When called for a USB interface, @dev->parent lock must be held.
517 */
518void device_release_driver(struct device *dev)
519{
520    /*
521     * If anyone calls device_release_driver() recursively from
522     * within their ->remove callback for the same device, they
523     * will deadlock right here.
524     */
525    device_lock(dev);
526    __device_release_driver(dev);
527    device_unlock(dev);
528}
529EXPORT_SYMBOL_GPL(device_release_driver);
530
531/**
532 * driver_detach - detach driver from all devices it controls.
533 * @drv: driver.
534 */
535void driver_detach(struct device_driver *drv)
536{
537    struct device_private *dev_prv;
538    struct device *dev;
539
540    for (;;) {
541        spin_lock(&drv->p->klist_devices.k_lock);
542        if (list_empty(&drv->p->klist_devices.k_list)) {
543            spin_unlock(&drv->p->klist_devices.k_lock);
544            break;
545        }
546        dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
547                     struct device_private,
548                     knode_driver.n_node);
549        dev = dev_prv->device;
550        get_device(dev);
551        spin_unlock(&drv->p->klist_devices.k_lock);
552
553        if (dev->parent) /* Needed for USB */
554            device_lock(dev->parent);
555        device_lock(dev);
556        if (dev->driver == drv)
557            __device_release_driver(dev);
558        device_unlock(dev);
559        if (dev->parent)
560            device_unlock(dev->parent);
561        put_device(dev);
562    }
563}
564
565/*
566 * These exports can't be _GPL due to .h files using this within them, and it
567 * might break something that was previously working...
568 */
569void *dev_get_drvdata(const struct device *dev)
570{
571    if (dev && dev->p)
572        return dev->p->driver_data;
573    return NULL;
574}
575EXPORT_SYMBOL(dev_get_drvdata);
576
577int dev_set_drvdata(struct device *dev, void *data)
578{
579    int error;
580
581    if (!dev->p) {
582        error = device_private_init(dev);
583        if (error)
584            return error;
585    }
586    dev->p->driver_data = data;
587    return 0;
588}
589EXPORT_SYMBOL(dev_set_drvdata);
590

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