From 3d060aeb72113cda0acf906bfe26914fc689506a Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Mon, 27 Jul 2015 18:04:00 +0300 Subject: [PATCH] driver core: implement device_for_each_child_reverse() The new function device_for_each_child_reverse() is helpful to traverse the registered devices in a reversed order, e.g. in the case when an operation on each device should be done first on the last added device, then on one before last and so on. Signed-off-by: Andy Shevchenko Acked-by: Greg Kroah-Hartman Signed-off-by: Lee Jones --- drivers/base/core.c | 43 ++++++++++++++++++++++++++++++++++++++++++ include/linux/device.h | 2 ++ 2 files changed, 45 insertions(+) diff --git a/drivers/base/core.c b/drivers/base/core.c index dafae6d2f7ac..7d6279554afc 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1252,6 +1252,19 @@ void device_unregister(struct device *dev) } EXPORT_SYMBOL_GPL(device_unregister); +static struct device *prev_device(struct klist_iter *i) +{ + struct klist_node *n = klist_prev(i); + struct device *dev = NULL; + struct device_private *p; + + if (n) { + p = to_device_private_parent(n); + dev = p->device; + } + return dev; +} + static struct device *next_device(struct klist_iter *i) { struct klist_node *n = klist_next(i); @@ -1340,6 +1353,36 @@ int device_for_each_child(struct device *parent, void *data, } EXPORT_SYMBOL_GPL(device_for_each_child); +/** + * device_for_each_child_reverse - device child iterator in reversed order. + * @parent: parent struct device. + * @fn: function to be called for each device. + * @data: data for the callback. + * + * Iterate over @parent's child devices, and call @fn for each, + * passing it @data. + * + * We check the return of @fn each time. If it returns anything + * other than 0, we break out and return that value. + */ +int device_for_each_child_reverse(struct device *parent, void *data, + int (*fn)(struct device *dev, void *data)) +{ + struct klist_iter i; + struct device *child; + int error = 0; + + if (!parent->p) + return 0; + + klist_iter_init(&parent->p->klist_children, &i); + while ((child = prev_device(&i)) && !error) + error = fn(child, data); + klist_iter_exit(&i); + return error; +} +EXPORT_SYMBOL_GPL(device_for_each_child_reverse); + /** * device_find_child - device iterator for locating a particular device. * @parent: parent struct device diff --git a/include/linux/device.h b/include/linux/device.h index 5a31bf3a4024..af6fbc35d8a6 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -958,6 +958,8 @@ extern int __must_check device_add(struct device *dev); extern void device_del(struct device *dev); extern int device_for_each_child(struct device *dev, void *data, int (*fn)(struct device *dev, void *data)); +extern int device_for_each_child_reverse(struct device *dev, void *data, + int (*fn)(struct device *dev, void *data)); extern struct device *device_find_child(struct device *dev, void *data, int (*match)(struct device *dev, void *data)); extern int device_rename(struct device *dev, const char *new_name); -- 2.20.1