linux-kernel - [RFC PATCH 03/12] of: base: record root node in interator and use it for phandle lookup

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Message-Id: <20210208222203.22335-4-info@metux.net>
Date:   Mon,  8 Feb 2021 23:21:54 +0100
From:   "Enrico Weigelt, metux IT consult" <info@...ux.net>
To:     linux-kernel@...r.kernel.org
Cc:     rafael@...nel.org, info@...ux.net, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, robh+dt@...nel.org,
        frowand.list@...il.com, pantelis.antoniou@...sulko.com,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org
Subject: [RFC PATCH 03/12] of: base: record root node in interator and use it for phandle lookup

For detached oftree support, find the root node and record it, on iterator
creation. If we find the root of the global oftree, record NULL, in order to
have a clear distinction between detached and non-detached cases. The recorded
root node is then used for resolving phandles.

Note that in the detached case, phandle cache can't be used, so we have a
little performance penalty on repeated phandle lookups.

Signed-off-by: Enrico Weigelt, metux IT consult <info@...ux.net>
---
 drivers/of/base.c  | 13 ++++++++++++-
 include/linux/of.h |  1 +
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 6b3d1e817808..e5ef611ed233 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1249,6 +1249,7 @@ int of_phandle_iterator_init(struct of_phandle_iterator *it,
 {
 	const __be32 *list;
 	int size;
+	struct device_node *walk;
 
 	memset(it, 0, sizeof(*it));
 
@@ -1270,6 +1271,16 @@ int of_phandle_iterator_init(struct of_phandle_iterator *it,
 	it->phandle_end = list;
 	it->cur = list;
 
+	/*
+	 * find the root of our tree and record it, if we're dealing with an
+	 * detached oftree - in non-detached case, we record NULL, for clear
+	 * distinction between these two cases.
+	 */
+	for (walk=(struct device_node*)np;
+	     walk->parent;
+	     walk=(struct device_node*)walk->parent);
+	it->root = ((walk == of_root) ? NULL : walk);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_phandle_iterator_init);
@@ -1297,7 +1308,7 @@ int of_phandle_iterator_next(struct of_phandle_iterator *it)
 		 * Find the provider node and parse the #*-cells property to
 		 * determine the argument length.
 		 */
-		it->node = of_find_node_by_phandle(it->phandle);
+		it->node = of_find_node_by_phandle_from(it->root, it->phandle);
 
 		if (it->cells_name) {
 			if (!it->node) {
diff --git a/include/linux/of.h b/include/linux/of.h
index c285141653e5..dbf2c7442389 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -82,6 +82,7 @@ struct of_phandle_iterator {
 	const char *cells_name;
 	int cell_count;
 	const struct device_node *parent;
+	struct device_node *root;
 
 	/* List size information */
 	const __be32 *list_end;
-- 
2.11.0