path: root/drivers/base/dd.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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
 * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2007-2009 Novell Inc.
 */

#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/dma-map-ops.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/async.h>
#include <linux/pm_runtime.h>
#include <linux/pinctrl/devinfo.h>
#include <linux/slab.h>

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

/*
 * Deferred Probe infrastructure.
 *
 * Sometimes driver probe order matters, but the kernel doesn't always have
 * dependency information which means some drivers will get probed before a
 * resource it depends on is available.  For example, an SDHCI driver may
 * first need a GPIO line from an i2c GPIO controller before it can be
 * initialized.  If a required resource is not available yet, a driver can
 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
 *
 * Deferred probe maintains two lists of devices, a pending list and an active
 * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
 * pending list.  A successful driver probe will trigger moving all devices
 * from the pending to the active list so that the workqueue will eventually
 * retry them.
 *
 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
 * of the (struct device*)->p->deferred_probe pointers are manipulated
 */
static DEFINE_MUTEX(deferred_probe_mutex);
static LIST_HEAD(deferred_probe_pending_list);
static LIST_HEAD(deferred_probe_active_list);
static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
static bool initcalls_done;

/* Save the async probe drivers' name from kernel cmdline */
#define ASYNC_DRV_NAMES_MAX_LEN	256
static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
static bool async_probe_default;

/*
 * In some cases, like suspend to RAM or hibernation, It might be reasonable
 * to prohibit probing of devices as it could be unsafe.
 * Once defer_all_probes is true all drivers probes will be forcibly deferred.
 */
static bool defer_all_probes;

static void __device_set_deferred_probe_reason(const struct device *dev, char *reason)
{
	kfree(dev->p->deferred_probe_reason);
	dev->p->deferred_probe_reason = reason;
}

/*
 * deferred_probe_work_func() - Retry probing devices in the active list.
 */
static void deferred_probe_work_func(struct work_struct *work)
{
	struct device *dev;
	struct device_private *private;
	/*
	 * This block processes every device in the deferred 'active' list.
	 * Each device is removed from the active list and passed to
	 * bus_probe_device() to re-attempt the probe.  The loop continues
	 * until every device in the active list is removed and retried.
	 *
	 * Note: Once the device is removed from the list and the mutex is
	 * released, it is possible for the device get freed by another thread
	 * and cause a illegal pointer dereference.  This code uses
	 * get/put_device() to ensure the device structure cannot disappear
	 * from under our feet.
	 */
	mutex_lock(&deferred_probe_mutex);
	while (!list_empty(&deferred_probe_active_list)) {
		private = list_first_entry(&deferred_probe_active_list,
					typeof(*dev->p), deferred_probe);
		dev = private->device