[PATCH v1 1/3] driver core: Support asynchronous driver shutdown

[Tanjore Suresh <tansuresh@google.com>]

This changes the bus driver interface with additional entry points
to enable devices to implement asynchronous shutdown. The existing
synchronous interface to shutdown is unmodified and retained for
backward compatibility.

This changes the common device shutdown code to enable devices to
participate in asynchronous shutdown implementation.

Signed-off-by: Tanjore Suresh <tansuresh@google.com>
---
 drivers/base/core.c        | 39 +++++++++++++++++++++++++++++++++++++-
 include/linux/device/bus.h | 10 ++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3d6430eb0c6a..359e7067e8b8 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4479,6 +4479,7 @@ EXPORT_SYMBOL_GPL(device_change_owner);
 void device_shutdown(void)
 {
 	struct device *dev, *parent;
+	LIST_HEAD(async_shutdown_list);
 
 	wait_for_device_probe();
 	device_block_probing();
@@ -4523,7 +4524,14 @@ void device_shutdown(void)
 				dev_info(dev, "shutdown_pre\n");
 			dev->class->shutdown_pre(dev);
 		}
-		if (dev->bus && dev->bus->shutdown) {
+
+		if (dev->bus && dev->bus->shutdown_pre) {
+			if (initcall_debug)
+				dev_info(dev, "shutdown_pre\n");
+			dev->bus->shutdown_pre(dev);
+			list_add(&dev->kobj.entry,
+				&async_shutdown_list);
+		} else if (dev->bus && dev->bus->shutdown) {
 			if (initcall_debug)
 				dev_info(dev, "shutdown\n");
 			dev->bus->shutdown(dev);
@@ -4543,6 +4551,35 @@ void device_shutdown(void)
 		spin_lock(&devices_kset->list_lock);
 	}
 	spin_unlock(&devices_kset->list_lock);
+
+	/*
+	 * Second pass spin for only devices, that have configured
+	 * Asynchronous shutdown.
+	 */
+	while (!list_empty(&async_shutdown_list)) {
+		dev = list_entry(async_shutdown_list.next, struct device,
+				kobj.entry);
+		parent = get_device(dev->parent);
+		get_device(dev);
+		/*
+		 * Make sure the device is off the  list
+		 */
+		list_del_init(&dev->kobj.entry);
+		if (parent)
+			device_lock(parent);
+		device_lock(dev);
+		if (dev->bus && dev->bus->shutdown_post) {
+			if (initcall_debug)
+				dev_info(dev,
+				"shutdown_post called\n");
+			dev->bus->shutdown_post(dev);
+		}
+		device_unlock(dev);
+		if (parent)
+			device_unlock(parent);
+		put_device(dev);
+		put_device(parent);
+	}
 }
 
 /*
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index a039ab809753..e261819601e9 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -49,6 +49,14 @@ struct fwnode_handle;
  *		will never get called until they do.
  * @remove:	Called when a device removed from this bus.
  * @shutdown:	Called at shut-down time to quiesce the device.
+ * @shutdown_pre:	Called at the shutdown-time to start the shutdown
+ *			process on the device. This entry point will be called
+ *			only when the bus driver has indicated it would like
+ *			to participate in asynchronous shutdown completion.
+ * @shutdown_post:	Called at shutdown-time  to complete the shutdown
+ *			process of the device. This entry point will be called
+ *			only when the bus drive has indicated it would like to
+ *			participate in the asynchronous shutdown completion.
  *
  * @online:	Called to put the device back online (after offlining it).
  * @offline:	Called to put the device offline for hot-removal. May fail.
@@ -93,6 +101,8 @@ struct bus_type {
 	void (*sync_state)(struct device *dev);
 	void (*remove)(struct device *dev);
 	void (*shutdown)(struct device *dev);
+	void (*shutdown_pre)(struct device *dev);
+	void (*shutdown_post)(struct device *dev);
 
 	int (*online)(struct device *dev);
 	int (*offline)(struct device *dev);
-- 
2.35.1.1021.g381101b075-goog