Driver core: add bus_sort_breadthfirst() function

The PCI core wants to reorder the devices in the bus list.  So move this
functionality out of the pci core and into the driver core so that
anyone else can also do this if needed.  This also lets us change how
struct device is attached to drivers in the future without messing with
the PCI core.

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 50 insertions, 0 deletions

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 39b9b58c697..5aee1c0169e 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -980,6 +980,56 @@ struct klist *bus_get_device_klist(struct bus_type *bus)
 }
 EXPORT_SYMBOL_GPL(bus_get_device_klist);
 
+/*
+ * Yes, this forcably breaks the klist abstraction temporarily.  It
+ * just wants to sort the klist, not change reference counts and
+ * take/drop locks rapidly in the process.  It does all this while
+ * holding the lock for the list, so objects can't otherwise be
+ * added/removed while we're swizzling.
+ */
+static void device_insertion_sort_klist(struct device *a, struct list_head *list,
+					int (*compare)(const struct device *a,
+							const struct device *b))
+{
+	struct list_head *pos;
+	struct klist_node *n;
+	struct device *b;
+
+	list_for_each(pos, list) {
+		n = container_of(pos, struct klist_node, n_node);
+		b = container_of(n, struct device, knode_bus);
+		if (compare(a, b) <= 0) {
+			list_move_tail(&a->knode_bus.n_node,
+				       &b->knode_bus.n_node);
+			return;
+		}
+	}
+	list_move_tail(&a->knode_bus.n_node, list);
+}
+
+void bus_sort_breadthfirst(struct bus_type *bus,
+			   int (*compare)(const struct device *a,
+					  const struct device *b))
+{
+	LIST_HEAD(sorted_devices);
+	struct list_head *pos, *tmp;
+	struct klist_node *n;
+	struct device *dev;
+	struct klist *device_klist;
+
+	device_klist = bus_get_device_klist(bus);
+
+	spin_lock(&device_klist->k_lock);
+	list_for_each_safe(pos, tmp, &device_klist->k_list) {
+		n = container_of(pos, struct klist_node, n_node);
+		dev = container_of(n, struct device, knode_bus);
+		device_insertion_sort_klist(dev, &sorted_devices, compare);
+	}
+	list_splice(&sorted_devices, &device_klist->k_list);
+	spin_unlock(&device_klist->k_lock);
+}
+EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
+
 int __init buses_init(void)
 {
 	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);