[PATCH 1/6] resource: implement resource walker

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

We currently keep track of regions with the SDRAM by requesting a struct
resource from the memory bank. We will make additional use of that to
request memory handed out to EFI applications when barebox is being used
as EFI loader.

For that purpose, we need an easy way to walk the requested memory
region and especially the gaps between them.

Add a new resource_iter API for exactly this purpose.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 common/resource.c      | 112 +++++++++++++++++++++++++++++++++++++++++
 include/linux/ioport.h |   7 +++
 2 files changed, 119 insertions(+)

diff --git a/common/resource.c b/common/resource.c
index 152f5a502a1e..c8623b9c40a6 100644
--- a/common/resource.c
+++ b/common/resource.c
@@ -169,6 +169,118 @@ struct resource *request_ioport_region(const char *name,
 	return res;
 }
 
+static struct resource *
+resource_iter_gap(struct resource *parent, struct resource *before,
+		  struct resource *gap, struct resource *after)
+{
+	*gap = (struct resource) {};
+
+	gap->attrs = parent->attrs;
+	gap->type = parent->type;
+	gap->flags = IORESOURCE_UNSET | parent->flags;
+	gap->parent = parent;
+	INIT_LIST_HEAD(&gap->children);
+
+	if (before) {
+		gap->start = before->end + 1;
+		gap->sibling.prev = &before->sibling;
+	} else {
+		gap->start = parent->start;
+		gap->sibling.prev = &parent->children;
+	}
+
+	if (after) {
+		gap->end = after->start - 1;
+		gap->sibling.next = &after->sibling;
+	} else {
+		gap->end = parent->end;
+		gap->sibling.next = &parent->children;
+	}
+
+	return gap;
+}
+
+struct resource *
+resource_iter_first(struct resource *parent, struct resource *gap)
+{
+	struct resource *child;
+
+	if (!parent || region_is_gap(parent))
+		return NULL;
+
+	child = list_first_entry_or_null(&parent->children,
+					 struct resource, sibling);
+	if (!gap || (child && parent->start == child->start))
+		return child;
+
+	return resource_iter_gap(parent, NULL, gap, child);
+}
+
+struct resource *
+resource_iter_last(struct resource *parent, struct resource *gap)
+{
+	struct resource *child;
+
+	if (!parent || region_is_gap(parent))
+		return NULL;
+
+	child = list_last_entry_or_null(&parent->children,
+					struct resource, sibling);
+	if (!gap || (child && parent->end == child->end))
+		return child;
+
+	return resource_iter_gap(parent, child, gap, NULL);
+}
+
+struct resource *
+resource_iter_next(struct resource *current, struct resource *gap)
+{
+	struct resource *parent, *cursor, *next = NULL;
+
+	if (!current || !current->parent)
+		return NULL;
+
+	parent = current->parent;
+	if (current->end == parent->end)
+		return NULL;
+
+	cursor = current;
+	list_for_each_entry_continue(cursor, &parent->children, sibling) {
+		next = cursor;
+		break;
+	}
+
+	if (!gap || (next && resource_adjacent(current, next)))
+		return next;
+
+	return resource_iter_gap(parent, current, gap, next);
+}
+
+struct resource *
+resource_iter_prev(struct resource *current,
+		       struct resource *gap)
+{
+	struct resource *parent, *cursor, *prev = NULL;
+
+	if (!current || !current->parent)
+		return NULL;
+
+	parent = current->parent;
+	if (current->start == parent->start)
+		return NULL;
+
+	cursor = current;
+	list_for_each_entry_continue_reverse(cursor, &parent->children, sibling) {
+		prev = cursor;
+		break;
+	}
+
+	if (!gap || (prev && resource_adjacent(prev, current)))
+		return prev;
+
+	return resource_iter_gap(parent, prev, gap, current);
+}
+
 struct resource_entry *resource_list_create_entry(struct resource *res,
 						  size_t extra_size)
 {
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index e24984f7f722..1b5dfdcb373d 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -265,5 +265,12 @@ static inline void resource_set_range(struct resource *res,
 	resource_set_size(res, size);
 }
 
+#define region_is_gap(region) ((region)->flags & IORESOURCE_UNSET)
+
+struct resource *resource_iter_first(struct resource *current, struct resource *gap);
+struct resource *resource_iter_last(struct resource *current, struct resource *gap);
+struct resource *resource_iter_prev(struct resource *current, struct resource *gap);
+struct resource *resource_iter_next(struct resource *current, struct resource *gap);
+
 #endif /* __ASSEMBLY__ */
 #endif	/* _LINUX_IOPORT_H */
-- 
2.47.3