[Skiboot] [PATCH v2 2/4] core/device.c: Sort nodes with name at unit names by unit

[Oliver O'Halloran]

When unflattening (or building from hdat) a device tree child nodes are added in
the order in which they are encountered. For nodes that have a <basename>@<unit>
style name with a common basename it is useful to have them in the tree sorted
by the unit in ascending order. Currently this requires the source data to
present them in sorted order, but this isn't always the case.

This patch modifies the node insertion process to insert new nodes in the
correct location so the list of child nodes is sorted.

Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 core/device.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 52 insertions(+), 4 deletions(-)

diff --git a/core/device.c b/core/device.c
index c5f8634..baa37c5 100644
--- a/core/device.c
+++ b/core/device.c
@@ -65,21 +65,69 @@ struct dt_node *dt_new_root(const char *name)
 	return new_node(name);
 }
 
+static const char *get_unitname(const struct dt_node *node)
+{
+	const char *c = strchr(node->name, '@');
+
+	if (!c)
+		return NULL;
+
+	return c + 1;
+}
+
+static int dt_cmp_subnodes(const struct dt_node *a, const struct dt_node *b)
+{
+	const char *a_unit = get_unitname(a);
+	const char *b_unit = get_unitname(b);
+
+	ptrdiff_t basenamelen = a_unit - a->name;
+
+	/* sort hex unit addresses by number */
+	if (a_unit && b_unit && !strncmp(a->name, b->name, basenamelen)) {
+		unsigned long long a_num, b_num;
+		char *a_end, *b_end;
+
+		a_num = strtoul(a_unit, &a_end, 16);
+		b_num = strtoul(b_unit, &b_end, 16);
+
+		/* only compare if the unit addr parsed correctly */
+		if (*a_end == 0 && *b_end == 0)
+			return (a_num > b_num) - (a_num < b_num);
+	}
+
+	return strcmp(a->name, b->name);
+}
+
 bool dt_attach_root(struct dt_node *parent, struct dt_node *root)
 {
 	struct dt_node *node;
 
-	/* Look for duplicates */
-
 	assert(!root->parent);
+
+	if (list_empty(&parent->children)) {
+		list_add(&parent->children, &root->list);
+		root->parent = parent;
+
+		return true;
+	}
+
 	dt_for_each_child(parent, node) {
-		if (!strcmp(node->name, root->name)) {
+		int cmp = dt_cmp_subnodes(node, root);
+
+		/* Look for duplicates */
+		if (cmp == 0) {
 			prerror("DT: %s failed, duplicate %s\n",
 				__func__, root->name);
 			return false;
 		}
+		
+		/* insert before the first node that's larger 
+		 * the the node we're inserting */
+		if (cmp > 0) 
+			break;
 	}
-	list_add_tail(&parent->children, &root->list);
+
+	list_add_before(&parent->children, &root->list, &node->list);
 	root->parent = parent;
 
 	return true;
-- 
2.5.0