mailbox: Add device-managed registration functions

Add device-managed equivalents of the mbox_controller_register() and
mbox_controller_unregister() functions that can be used to have the
devres infrastructure automatically unregister mailbox controllers on
driver probe failure or driver removal. This can help remove a lot of
boiler plate code from drivers.

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/mailbox.c

@@ -515,3 +515,73 @@ void mbox_controller_unregister(struct mbox_controller *mbox)
 	mutex_unlock(&con_mutex);
 }
 EXPORT_SYMBOL_GPL(mbox_controller_unregister);
+
+static void __devm_mbox_controller_unregister(struct device *dev, void *res)
+{
+	struct mbox_controller **mbox = res;
+
+	mbox_controller_unregister(*mbox);
+}
+
+static int devm_mbox_controller_match(struct device *dev, void *res, void *data)
+{
+	struct mbox_controller **mbox = res;
+
+	if (WARN_ON(!mbox || !*mbox))
+		return 0;
+
+	return *mbox == data;
+}
+
+/**
+ * devm_mbox_controller_register() - managed mbox_controller_register()
+ * @dev: device owning the mailbox controller being registered
+ * @mbox: mailbox controller being registered
+ *
+ * This function adds a device-managed resource that will make sure that the
+ * mailbox controller, which is registered using mbox_controller_register()
+ * as part of this function, will be unregistered along with the rest of
+ * device-managed resources upon driver probe failure or driver removal.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int devm_mbox_controller_register(struct device *dev,
+				  struct mbox_controller *mbox)
+{
+	struct mbox_controller **ptr;
+	int err;
+
+	ptr = devres_alloc(__devm_mbox_controller_unregister, sizeof(*ptr),
+			   GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	err = mbox_controller_register(mbox);
+	if (err < 0) {
+		devres_free(ptr);
+		return err;
+	}
+
+	devres_add(dev, ptr);
+	*ptr = mbox;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_mbox_controller_register);
+
+/**
+ * devm_mbox_controller_unregister() - managed mbox_controller_unregister()
+ * @dev: device owning the mailbox controller being unregistered
+ * @mbox: mailbox controller being unregistered
+ *
+ * This function unregisters the mailbox controller and removes the device-
+ * managed resource that was set up to automatically unregister the mailbox
+ * controller on driver probe failure or driver removal. It's typically not
+ * necessary to call this function.
+ */
+void devm_mbox_controller_unregister(struct device *dev, struct mbox_controller *mbox)
+{
+	WARN_ON(devres_release(dev, __devm_mbox_controller_unregister,
+			       devm_mbox_controller_match, mbox));
+}
+EXPORT_SYMBOL_GPL(devm_mbox_controller_unregister);

include/linux/mailbox_controller.h

@@ -131,4 +131,9 @@ void mbox_controller_unregister(struct mbox_controller *mbox); /* can sleep */
 void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
 void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
 
+int devm_mbox_controller_register(struct device *dev,
+				  struct mbox_controller *mbox);
+void devm_mbox_controller_unregister(struct device *dev,
+				     struct mbox_controller *mbox);
+
 #endif /* __MAILBOX_CONTROLLER_H */