driver core: devres: introduce devres_for_each_res

This patch introduces one devres API of devres_for_each_res
so that the device's driver can iterate each resource it has
interest in.

The firmware loader will use the API to get each firmware name
from the device instance.
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/devres.c

@@ -143,6 +143,48 @@ void * devres_alloc(dr_release_t release, size_t size, gfp_t gfp)
 EXPORT_SYMBOL_GPL(devres_alloc);
 #endif
 
+/**
+ * devres_for_each_res - Resource iterator
+ * @dev: Device to iterate resource from
+ * @release: Look for resources associated with this release function
+ * @match: Match function (optional)
+ * @match_data: Data for the match function
+ * @fn: Function to be called for each matched resource.
+ * @data: Data for @fn, the 3rd parameter of @fn
+ *
+ * Call @fn for each devres of @dev which is associated with @release
+ * and for which @match returns 1.
+ *
+ * RETURNS:
+ * 	void
+ */
+void devres_for_each_res(struct device *dev, dr_release_t release,
+			dr_match_t match, void *match_data,
+			void (*fn)(struct device *, void *, void *),
+			void *data)
+{
+	struct devres_node *node;
+	struct devres_node *tmp;
+	unsigned long flags;
+
+	if (!fn)
+		return;
+
+	spin_lock_irqsave(&dev->devres_lock, flags);
+	list_for_each_entry_safe_reverse(node, tmp,
+			&dev->devres_head, entry) {
+		struct devres *dr = container_of(node, struct devres, node);
+
+		if (node->release != release)
+			continue;
+		if (match && !match(dev, dr->data, match_data))
+			continue;
+		fn(dev, dr->data, data);
+	}
+	spin_unlock_irqrestore(&dev->devres_lock, flags);
+}
+EXPORT_SYMBOL_GPL(devres_for_each_res);
+
 /**
  * devres_free - Free device resource data
  * @res: Pointer to devres data to free

include/linux/device.h

@@ -536,6 +536,10 @@ extern void *__devres_alloc(dr_release_t release, size_t size, gfp_t gfp,
 #else
 extern void *devres_alloc(dr_release_t release, size_t size, gfp_t gfp);
 #endif
+extern void devres_for_each_res(struct device *dev, dr_release_t release,
+				dr_match_t match, void *match_data,
+				void (*fn)(struct device *, void *, void *),
+				void *data);
 extern void devres_free(void *res);
 extern void devres_add(struct device *dev, void *res);
 extern void *devres_find(struct device *dev, dr_release_t release,