devres: allow adding custom actions to the stack

Sometimes drivers need to execute one-off actions in their error handling
or device teardown paths. An example would be toggling a GPIO line to
reset the controlled device into predefined state.

To allow performing such actions when using managed resources let's allow
adding them to stack/group of devres resources.

Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 8731979..724957a 100644 (file)
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -670,6 +670,80 @@ int devres_release_group(struct device *dev, void *id)
 }
 EXPORT_SYMBOL_GPL(devres_release_group);
 
+/*
+ * Custom devres actions allow inserting a simple function call
+ * into the teadown sequence.
+ */
+
+struct action_devres {
+       void *data;
+       void (*action)(void *);
+};
+
+static int devm_action_match(struct device *dev, void *res, void *p)
+{
+       struct action_devres *devres = res;
+       struct action_devres *target = p;
+
+       return devres->action == target->action &&
+              devres->data == target->data;
+}
+
+static void devm_action_release(struct device *dev, void *res)
+{
+       struct action_devres *devres = res;
+
+       devres->action(devres->data);
+}
+
+/**
+ * devm_add_action() - add a custom action to list of managed resources
+ * @dev: Device that owns the action
+ * @action: Function that should be called
+ * @data: Pointer to data passed to @action implementation
+ *
+ * This adds a custom action to the list of managed resources so that
+ * it gets executed as part of standard resource unwinding.
+ */
+int devm_add_action(struct device *dev, void (*action)(void *), void *data)
+{
+       struct action_devres *devres;
+
+       devres = devres_alloc(devm_action_release,
+                             sizeof(struct action_devres), GFP_KERNEL);
+       if (!devres)
+               return -ENOMEM;
+
+       devres->data = data;
+       devres->action = action;
+
+       devres_add(dev, devres);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(devm_add_action);
+
+/**
+ * devm_remove_action() - removes previously added custom action
+ * @dev: Device that owns the action
+ * @action: Function implementing the action
+ * @data: Pointer to data passed to @action implementation
+ *
+ * Removes instance of @action previously added by devm_add_action().
+ * Both action and data should match one of the existing entries.
+ */
+void devm_remove_action(struct device *dev, void (*action)(void *), void *data)
+{
+       struct action_devres devres = {
+               .data = data,
+               .action = action,
+       };
+
+       WARN_ON(devres_destroy(dev, devm_action_release, devm_action_match,
+                              &devres));
+
+}
+EXPORT_SYMBOL_GPL(devm_remove_action);
+
 /*
  * Managed kzalloc/kfree
  */

diff --git a/include/linux/device.h b/include/linux/device.h
index 86ef6ab..854b247 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -567,6 +567,10 @@ extern void devm_kfree(struct device *dev, void *p);
 void __iomem *devm_request_and_ioremap(struct device *dev,
                        struct resource *res);
 
+/* 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);
+
 struct device_dma_parameters {
        /*
         * a low level driver may set these to teach IOMMU code about