[PATCH 1/6] drivers/base/devres: Introduce devm_release_action()

[Dan Williams <dan.j.williams@xxxxxxxxx>]

The devm_add_action() facility allows a resource allocation routine to
add custom devm semantics. One such user is devm_memremap_pages().

There is now a need to manually trigger devm_memremap_pages_release().
Introduce devm_release_action() so the release action can be triggered
via a new devm_memunmap_pages() api in a follow-on change.

Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 drivers/base/devres.c  |   24 +++++++++++++++++++++++-
 include/linux/device.h |    1 +
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index e038e2b3b7ea..0bbb328bd17f 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -755,10 +755,32 @@ void devm_remove_action(struct device *dev, void (*action)(void *), void *data)
 
 	WARN_ON(devres_destroy(dev, devm_action_release, devm_action_match,
 			       &devres));
-
 }
 EXPORT_SYMBOL_GPL(devm_remove_action);
 
+/**
+ * devm_release_action() - release previously added custom action
+ * @dev: Device that owns the action
+ * @action: Function implementing the action
+ * @data: Pointer to data passed to @action implementation
+ *
+ * Releases and removes instance of @action previously added by
+ * devm_add_action().  Both action and data should match one of the
+ * existing entries.
+ */
+void devm_release_action(struct device *dev, void (*action)(void *), void *data)
+{
+	struct action_devres devres = {
+		.data = data,
+		.action = action,
+	};
+
+	WARN_ON(devres_release(dev, devm_action_release, devm_action_match,
+			       &devres));
+
+}
+EXPORT_SYMBOL_GPL(devm_release_action);
+
 /*
  * Managed kmalloc/kfree
  */
diff --git a/include/linux/device.h b/include/linux/device.h
index b425a7ee04ce..02a3e45de9af 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -715,6 +715,7 @@ void __iomem *devm_of_iomap(struct device *dev,
 /* allows to add/remove a custom action to devres stack */
 int devm_add_action(struct device *dev, void (*action)(void *), void *data);
 void devm_remove_action(struct device *dev, void (*action)(void *), void *data);
+void devm_release_action(struct device *dev, void (*action)(void *), void *data);
 
 static inline int devm_add_action_or_reset(struct device *dev,
 					   void (*action)(void *), void *data)