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#include <linux/pinctrl/devinfo.h>
28
29#include "base.h"
30#include "power/power.h"
31
32/*
33 * Deferred Probe infrastructure.
34 *
35 * Sometimes driver probe order matters, but the kernel doesn't always have
36 * dependency information which means some drivers will get probed before a
37 * resource it depends on is available. For example, an SDHCI driver may
38 * first need a GPIO line from an i2c GPIO controller before it can be
39 * initialized. If a required resource is not available yet, a driver can
40 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
41 *
42 * Deferred probe maintains two lists of devices, a pending list and an active
43 * list. A driver returning -EPROBE_DEFER causes the device to be added to the
44 * pending list. A successful driver probe will trigger moving all devices
45 * from the pending to the active list so that the workqueue will eventually
46 * retry them.
47 *
48 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
49 * of the (struct device*)->p->deferred_probe pointers are manipulated
50 */
51static DEFINE_MUTEX(deferred_probe_mutex);
52static LIST_HEAD(deferred_probe_pending_list);
53static LIST_HEAD(deferred_probe_active_list);
54static struct workqueue_struct *deferred_wq;
55
56/**
57 * deferred_probe_work_func() - Retry probing devices in the active list.
58 */
59static void deferred_probe_work_func(struct work_struct *work)
60{
61    struct device *dev;
62    struct device_private *private;
63    /*
64     * This block processes every device in the deferred 'active' list.
65     * Each device is removed from the active list and passed to
66     * bus_probe_device() to re-attempt the probe. The loop continues
67     * until every device in the active list is removed and retried.
68     *
69     * Note: Once the device is removed from the list and the mutex is
70     * released, it is possible for the device get freed by another thread
71     * and cause a illegal pointer dereference. This code uses
72     * get/put_device() to ensure the device structure cannot disappear
73     * from under our feet.
74     */
75    mutex_lock(&deferred_probe_mutex);
76    while (!list_empty(&deferred_probe_active_list)) {
77        private = list_first_entry(&deferred_probe_active_list,
78                    typeof(*dev->p), deferred_probe);
79        dev = private->device;
80        list_del_init(&private->deferred_probe);
81
82        get_device(dev);
83
84        /*
85         * Drop the mutex while probing each device; the probe path may
86         * manipulate the deferred list
87         */
88        mutex_unlock(&deferred_probe_mutex);
89
90        /*
91         * Force the device to the end of the dpm_list since
92         * the PM code assumes that the order we add things to
93         * the list is a good order for suspend but deferred
94         * probe makes that very unsafe.
95         */
96        device_pm_lock();
97        device_pm_move_last(dev);
98        device_pm_unlock();
99
100        dev_dbg(dev, "Retrying from deferred list\n");
101        bus_probe_device(dev);
102
103        mutex_lock(&deferred_probe_mutex);
104
105        put_device(dev);
106    }
107    mutex_unlock(&deferred_probe_mutex);
108}
109static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
110
111static void driver_deferred_probe_add(struct device *dev)
112{
113    mutex_lock(&deferred_probe_mutex);
114    if (list_empty(&dev->p->deferred_probe)) {
115        dev_dbg(dev, "Added to deferred list\n");
116        list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
117    }
118    mutex_unlock(&deferred_probe_mutex);
119}
120
121void driver_deferred_probe_del(struct device *dev)
122{
123    mutex_lock(&deferred_probe_mutex);
124    if (!list_empty(&dev->p->deferred_probe)) {
125        dev_dbg(dev, "Removed from deferred list\n");
126        list_del_init(&dev->p->deferred_probe);
127    }
128    mutex_unlock(&deferred_probe_mutex);
129}
130
131static bool driver_deferred_probe_enable = false;
132/**
133 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
134 *
135 * This functions moves all devices from the pending list to the active
136 * list and schedules the deferred probe workqueue to process them. It
137 * should be called anytime a driver is successfully bound to a device.
138 */
139static void driver_deferred_probe_trigger(void)
140{
141    if (!driver_deferred_probe_enable)
142        return;
143
144    /*
145     * A successful probe means that all the devices in the pending list
146     * should be triggered to be reprobed. Move all the deferred devices
147     * into the active list so they can be retried by the workqueue
148     */
149    mutex_lock(&deferred_probe_mutex);
150    list_splice_tail_init(&deferred_probe_pending_list,
151                  &deferred_probe_active_list);
152    mutex_unlock(&deferred_probe_mutex);
153
154    /*
155     * Kick the re-probe thread. It may already be scheduled, but it is
156     * safe to kick it again.
157     */
158    queue_work(deferred_wq, &deferred_probe_work);
159}
160
161/**
162 * deferred_probe_initcall() - Enable probing of deferred devices
163 *
164 * We don't want to get in the way when the bulk of drivers are getting probed.
165 * Instead, this initcall makes sure that deferred probing is delayed until
166 * late_initcall time.
167 */
168static int deferred_probe_initcall(void)
169{
170    deferred_wq = create_singlethread_workqueue("deferwq");
171    if (WARN_ON(!deferred_wq))
172        return -ENOMEM;
173
174    driver_deferred_probe_enable = true;
175    driver_deferred_probe_trigger();
176    /* Sort as many dependencies as possible before exiting initcalls */
177    flush_workqueue(deferred_wq);
178    return 0;
179}
180late_initcall(deferred_probe_initcall);
181
182static void driver_bound(struct device *dev)
183{
184    if (klist_node_attached(&dev->p->knode_driver)) {
185        printk(KERN_WARNING "%s: device %s already bound\n",
186            __func__, kobject_name(&dev->kobj));
187        return;
188    }
189
190    pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
191         __func__, dev->driver->name);
192
193    klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
194
195    /*
196     * Make sure the device is no longer in one of the deferred lists and
197     * kick off retrying all pending devices
198     */
199    driver_deferred_probe_del(dev);
200    driver_deferred_probe_trigger();
201
202    if (dev->bus)
203        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
204                         BUS_NOTIFY_BOUND_DRIVER, dev);
205}
206
207static int driver_sysfs_add(struct device *dev)
208{
209    int ret;
210
211    if (dev->bus)
212        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
213                         BUS_NOTIFY_BIND_DRIVER, dev);
214
215    ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
216              kobject_name(&dev->kobj));
217    if (ret == 0) {
218        ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
219                    "driver");
220        if (ret)
221            sysfs_remove_link(&dev->driver->p->kobj,
222                    kobject_name(&dev->kobj));
223    }
224    return ret;
225}
226
227static void driver_sysfs_remove(struct device *dev)
228{
229    struct device_driver *drv = dev->driver;
230
231    if (drv) {
232        sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
233        sysfs_remove_link(&dev->kobj, "driver");
234    }
235}
236
237/**
238 * device_bind_driver - bind a driver to one device.
239 * @dev: device.
240 *
241 * Allow manual attachment of a driver to a device.
242 * Caller must have already set @dev->driver.
243 *
244 * Note that this does not modify the bus reference count
245 * nor take the bus's rwsem. Please verify those are accounted
246 * for before calling this. (It is ok to call with no other effort
247 * from a driver's probe() method.)
248 *
249 * This function must be called with the device lock held.
250 */
251int device_bind_driver(struct device *dev)
252{
253    int ret;
254
255    ret = driver_sysfs_add(dev);
256    if (!ret)
257        driver_bound(dev);
258    return ret;
259}
260EXPORT_SYMBOL_GPL(device_bind_driver);
261
262static atomic_t probe_count = ATOMIC_INIT(0);
263static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
264
265static int really_probe(struct device *dev, struct device_driver *drv)
266{
267    int ret = 0;
268
269    atomic_inc(&probe_count);
270    pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
271         drv->bus->name, __func__, drv->name, dev_name(dev));
272    WARN_ON(!list_empty(&dev->devres_head));
273
274    dev->driver = drv;
275
276    /* If using pinctrl, bind pins now before probing */
277    ret = pinctrl_bind_pins(dev);
278    if (ret)
279        goto probe_failed;
280
281    if (driver_sysfs_add(dev)) {
282        printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
283            __func__, dev_name(dev));
284        goto probe_failed;
285    }
286
287    if (dev->bus->probe) {
288        ret = dev->bus->probe(dev);
289        if (ret)
290            goto probe_failed;
291    } else if (drv->probe) {
292        ret = drv->probe(dev);
293        if (ret)
294            goto probe_failed;
295    }
296
297    driver_bound(dev);
298    ret = 1;
299    pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
300         drv->bus->name, __func__, dev_name(dev), drv->name);
301    goto done;
302
303probe_failed:
304    devres_release_all(dev);
305    driver_sysfs_remove(dev);
306    dev->driver = NULL;
307    dev_set_drvdata(dev, NULL);
308
309    if (ret == -EPROBE_DEFER) {
310        /* Driver requested deferred probing */
311        dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
312        driver_deferred_probe_add(dev);
313    } else if (ret != -ENODEV && ret != -ENXIO) {
314        /* driver matched but the probe failed */
315        printk(KERN_WARNING
316               "%s: probe of %s failed with error %d\n",
317               drv->name, dev_name(dev), ret);
318    } else {
319        pr_debug("%s: probe of %s rejects match %d\n",
320               drv->name, dev_name(dev), ret);
321    }
322    /*
323     * Ignore errors returned by ->probe so that the next driver can try
324     * its luck.
325     */
326    ret = 0;
327done:
328    atomic_dec(&probe_count);
329    wake_up(&probe_waitqueue);
330    return ret;
331}
332
333/**
334 * driver_probe_done
335 * Determine if the probe sequence is finished or not.
336 *
337 * Should somehow figure out how to use a semaphore, not an atomic variable...
338 */
339int driver_probe_done(void)
340{
341    pr_debug("%s: probe_count = %d\n", __func__,
342         atomic_read(&probe_count));
343    if (atomic_read(&probe_count))
344        return -EBUSY;
345    return 0;
346}
347
348/**
349 * wait_for_device_probe
350 * Wait for device probing to be completed.
351 */
352void wait_for_device_probe(void)
353{
354    /* wait for the known devices to complete their probing */
355    wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
356    async_synchronize_full();
357}
358EXPORT_SYMBOL_GPL(wait_for_device_probe);
359
360/**
361 * driver_probe_device - attempt to bind device & driver together
362 * @drv: driver to bind a device to
363 * @dev: device to try to bind to the driver
364 *
365 * This function returns -ENODEV if the device is not registered,
366 * 1 if the device is bound successfully and 0 otherwise.
367 *
368 * This function must be called with @dev lock held. When called for a
369 * USB interface, @dev->parent lock must be held as well.
370 */
371int driver_probe_device(struct device_driver *drv, struct device *dev)
372{
373    int ret = 0;
374
375    if (!device_is_registered(dev))
376        return -ENODEV;
377
378    pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
379         drv->bus->name, __func__, dev_name(dev), drv->name);
380
381    pm_runtime_barrier(dev);
382    ret = really_probe(dev, drv);
383    pm_runtime_idle(dev);
384
385    return ret;
386}
387
388static int __device_attach(struct device_driver *drv, void *data)
389{
390    struct device *dev = data;
391
392    if (!driver_match_device(drv, dev))
393        return 0;
394
395    return driver_probe_device(drv, dev);
396}
397
398/**
399 * device_attach - try to attach device to a driver.
400 * @dev: device.
401 *
402 * Walk the list of drivers that the bus has and call
403 * driver_probe_device() for each pair. If a compatible
404 * pair is found, break out and return.
405 *
406 * Returns 1 if the device was bound to a driver;
407 * 0 if no matching driver was found;
408 * -ENODEV if the device is not registered.
409 *
410 * When called for a USB interface, @dev->parent lock must be held.
411 */
412int device_attach(struct device *dev)
413{
414    int ret = 0;
415
416    device_lock(dev);
417    if (dev->driver) {
418        if (klist_node_attached(&dev->p->knode_driver)) {
419            ret = 1;
420            goto out_unlock;
421        }
422        ret = device_bind_driver(dev);
423        if (ret == 0)
424            ret = 1;
425        else {
426            dev->driver = NULL;
427            ret = 0;
428        }
429    } else {
430        ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
431        pm_runtime_idle(dev);
432    }
433out_unlock:
434    device_unlock(dev);
435    return ret;
436}
437EXPORT_SYMBOL_GPL(device_attach);
438
439static int __driver_attach(struct device *dev, void *data)
440{
441    struct device_driver *drv = data;
442
443    /*
444     * Lock device and try to bind to it. We drop the error
445     * here and always return 0, because we need to keep trying
446     * to bind to devices and some drivers will return an error
447     * simply if it didn't support the device.
448     *
449     * driver_probe_device() will spit a warning if there
450     * is an error.
451     */
452
453    if (!driver_match_device(drv, dev))
454        return 0;
455
456    if (dev->parent) /* Needed for USB */
457        device_lock(dev->parent);
458    device_lock(dev);
459    if (!dev->driver)
460        driver_probe_device(drv, dev);
461    device_unlock(dev);
462    if (dev->parent)
463        device_unlock(dev->parent);
464
465    return 0;
466}
467
468/**
469 * driver_attach - try to bind driver to devices.
470 * @drv: driver.
471 *
472 * Walk the list of devices that the bus has on it and try to
473 * match the driver with each one. If driver_probe_device()
474 * returns 0 and the @dev->driver is set, we've found a
475 * compatible pair.
476 */
477int driver_attach(struct device_driver *drv)
478{
479    return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
480}
481EXPORT_SYMBOL_GPL(driver_attach);
482
483/*
484 * __device_release_driver() must be called with @dev lock held.
485 * When called for a USB interface, @dev->parent lock must be held as well.
486 */
487static void __device_release_driver(struct device *dev)
488{
489    struct device_driver *drv;
490
491    drv = dev->driver;
492    if (drv) {
493        pm_runtime_get_sync(dev);
494
495        driver_sysfs_remove(dev);
496
497        if (dev->bus)
498            blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
499                             BUS_NOTIFY_UNBIND_DRIVER,
500                             dev);
501
502        pm_runtime_put_sync(dev);
503
504        if (dev->bus && dev->bus->remove)
505            dev->bus->remove(dev);
506        else if (drv->remove)
507            drv->remove(dev);
508        devres_release_all(dev);
509        dev->driver = NULL;
510        dev_set_drvdata(dev, NULL);
511        klist_remove(&dev->p->knode_driver);
512        if (dev->bus)
513            blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
514                             BUS_NOTIFY_UNBOUND_DRIVER,
515                             dev);
516
517    }
518}
519
520/**
521 * device_release_driver - manually detach device from driver.
522 * @dev: device.
523 *
524 * Manually detach device from driver.
525 * When called for a USB interface, @dev->parent lock must be held.
526 */
527void device_release_driver(struct device *dev)
528{
529    /*
530     * If anyone calls device_release_driver() recursively from
531     * within their ->remove callback for the same device, they
532     * will deadlock right here.
533     */
534    device_lock(dev);
535    __device_release_driver(dev);
536    device_unlock(dev);
537}
538EXPORT_SYMBOL_GPL(device_release_driver);
539
540/**
541 * driver_detach - detach driver from all devices it controls.
542 * @drv: driver.
543 */
544void driver_detach(struct device_driver *drv)
545{
546    struct device_private *dev_prv;
547    struct device *dev;
548
549    for (;;) {
550        spin_lock(&drv->p->klist_devices.k_lock);
551        if (list_empty(&drv->p->klist_devices.k_list)) {
552            spin_unlock(&drv->p->klist_devices.k_lock);
553            break;
554        }
555        dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
556                     struct device_private,
557                     knode_driver.n_node);
558        dev = dev_prv->device;
559        get_device(dev);
560        spin_unlock(&drv->p->klist_devices.k_lock);
561
562        if (dev->parent) /* Needed for USB */
563            device_lock(dev->parent);
564        device_lock(dev);
565        if (dev->driver == drv)
566            __device_release_driver(dev);
567        device_unlock(dev);
568        if (dev->parent)
569            device_unlock(dev->parent);
570        put_device(dev);
571    }
572}
573
574/*
575 * These exports can't be _GPL due to .h files using this within them, and it
576 * might break something that was previously working...
577 */
578void *dev_get_drvdata(const struct device *dev)
579{
580    if (dev && dev->p)
581        return dev->p->driver_data;
582    return NULL;
583}
584EXPORT_SYMBOL(dev_get_drvdata);
585
586int dev_set_drvdata(struct device *dev, void *data)
587{
588    int error;
589
590    if (!dev->p) {
591        error = device_private_init(dev);
592        if (error)
593            return error;
594    }
595    dev->p->driver_data = data;
596    return 0;
597}
598EXPORT_SYMBOL(dev_set_drvdata);
599

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