Revert "driver core: Add support for linking devices during device addition"

This reverts commit 5302dd7dd0b6d04c63cdce51d1e9fda9ef0be886.

Based on a lot of email and in-person discussions, this patch series is
being reworked to address a number of issues that were pointed out that
needed to be taken care of before it should be merged.  It will be
resubmitted with those changes hopefully soon.

Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Saravana Kannan <saravanak@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 0 insertions, 97 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 605905de0cca..066badad988c 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -44,8 +44,6 @@ early_param("sysfs.deprecated", sysfs_deprecated_setup);
 #endif
 
 /* Device links support. */
-static LIST_HEAD(wait_for_suppliers);
-static DEFINE_MUTEX(wfs_lock);
 
 #ifdef CONFIG_SRCU
 static DEFINE_MUTEX(device_links_lock);
@@ -420,51 +418,6 @@ struct device_link *device_link_add(struct device *consumer,
 }
 EXPORT_SYMBOL_GPL(device_link_add);
 
-/**
- * device_link_wait_for_supplier - Mark device as waiting for supplier
- * @consumer: Consumer device
- *
- * Marks the consumer device as waiting for suppliers to become available. The
- * consumer device will never be probed until it's unmarked as waiting for
- * suppliers. The caller is responsible for adding the link to the supplier
- * once the supplier device is present.
- *
- * This function is NOT meant to be called from the probe function of the
- * consumer but rather from code that creates/adds the consumer device.
- */
-static void device_link_wait_for_supplier(struct device *consumer)
-{
-	mutex_lock(&wfs_lock);
-	list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers);
-	mutex_unlock(&wfs_lock);
-}
-
-/**
- * device_link_check_waiting_consumers - Try to unmark waiting consumers
- *
- * Loops through all consumers waiting on suppliers and tries to add all their
- * supplier links. If that succeeds, the consumer device is unmarked as waiting
- * for suppliers. Otherwise, they are left marked as waiting on suppliers,
- *
- * The add_links bus callback is expected to return 0 if it has found and added
- * all the supplier links for the consumer device. It should return an error if
- * it isn't able to do so.
- *
- * The caller of device_link_wait_for_supplier() is expected to call this once
- * it's aware of potential suppliers becoming available.
- */
-static void device_link_check_waiting_consumers(void)
-{
-	struct device *dev, *tmp;
-
-	mutex_lock(&wfs_lock);
-	list_for_each_entry_safe(dev, tmp, &wait_for_suppliers,
-				 links.needs_suppliers)
-		if (!dev->bus->add_links(dev))
-			list_del_init(&dev->links.needs_suppliers);
-	mutex_unlock(&wfs_lock);
-}
-
 static void device_link_free(struct device_link *link)
 {
 	while (refcount_dec_not_one(&link->rpm_active))
@@ -599,19 +552,6 @@ int device_links_check_suppliers(struct device *dev)
 	struct device_link *link;
 	int ret = 0;
 
-	/*
-	 * If a device is waiting for one or more suppliers (in
-	 * wait_for_suppliers list), it is not ready to probe yet. So just
-	 * return -EPROBE_DEFER without having to check the links with existing
-	 * suppliers.
-	 */
-	mutex_lock(&wfs_lock);
-	if (!list_empty(&dev->links.needs_suppliers)) {
-		mutex_unlock(&wfs_lock);
-		return -EPROBE_DEFER;
-	}
-	mutex_unlock(&wfs_lock);
-
 	device_links_write_lock();
 
 	list_for_each_entry(link, &dev->links.suppliers, c_node) {
@@ -896,10 +836,6 @@ static void device_links_purge(struct device *dev)
 {
 	struct device_link *link, *ln;
 
-	mutex_lock(&wfs_lock);
-	list_del(&dev->links.needs_suppliers);
-	mutex_unlock(&wfs_lock);
-
 	/*
 	 * Delete all of the remaining links from this device to any other
 	 * devices (either consumers or suppliers).
@@ -1764,7 +1700,6 @@ void device_initialize(struct device *dev)
 #endif
 	INIT_LIST_HEAD(&dev->links.consumers);
 	INIT_LIST_HEAD(&dev->links.suppliers);
-	INIT_LIST_HEAD(&dev->links.needs_suppliers);
 	dev->links.status = DL_DEV_NO_DRIVER;
 }
 EXPORT_SYMBOL_GPL(device_initialize);
@@ -2251,24 +2186,6 @@ int device_add(struct device *dev)
 					     BUS_NOTIFY_ADD_DEVICE, dev);
 
 	kobject_uevent(&dev->kobj, KOBJ_ADD);
-
-	/*
-	 * Check if any of the other devices (consumers) have been waiting for
-	 * this device (supplier) to be added so that they can create a device
-	 * link to it.
-	 *
-	 * This needs to happen after device_pm_add() because device_link_add()
-	 * requires the supplier be registered before it's called.
-	 *
-	 * But this also needs to happe before bus_probe_device() to make sure
-	 * waiting consumers can link to it before the driver is bound to the
-	 * device and the driver sync_state callback is called for this device.
-	 */
-	device_link_check_waiting_consumers();
-
-	if (dev->bus && dev->bus->add_links && dev->bus->add_links(dev))
-		device_link_wait_for_supplier(dev);
-
 	bus_probe_device(dev);
 	if (parent)
 		klist_add_tail(&dev->p->knode_parent,
diff --git a/include/linux/device.h b/include/linux/device.h
index 73210745cc6b..ec598ede9455 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -78,17 +78,6 @@ extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
  *		-EPROBE_DEFER it will queue the device for deferred probing.
  * @uevent:	Called when a device is added, removed, or a few other things
  *		that generate uevents to add the environment variables.
- * @add_links:	Called, perhaps multiple times per device, after a device is
- *		added to this bus.  The function is expected to create device
- *		links to all the suppliers of the input device that are
- *		available at the time this function is called.  As in, the
- *		function should NOT stop at the first failed device link if
- *		other unlinked supplier devices are present in the system.
- *
- *		Return 0 if device links have been successfully created to all
- *		the suppliers of this device.  Return an error if some of the
- *		suppliers are not yet available and this function needs to be
- *		reattempted in the future.
  * @probe:	Called when a new device or driver add to this bus, and callback
  *		the specific driver's probe to initial the matched device.
  * @remove:	Called when a device removed from this bus.
@@ -133,7 +122,6 @@ struct bus_type {
 
 	int (*match)(struct device *dev, struct device_driver *drv);
 	int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
-	int (*add_links)(struct device *dev);
 	int (*probe)(struct device *dev);
 	int (*remove)(struct device *dev);
 	void (*shutdown)(struct device *dev);
@@ -1143,13 +1131,11 @@ enum dl_dev_state {
  * struct dev_links_info - Device data related to device links.
  * @suppliers: List of links to supplier devices.
  * @consumers: List of links to consumer devices.
- * @needs_suppliers: Hook to global list of devices waiting for suppliers.
  * @status: Driver status information.
  */
 struct dev_links_info {
 	struct list_head suppliers;
 	struct list_head consumers;
-	struct list_head needs_suppliers;
 	enum dl_dev_state status;
 };