of: add function to read a file as unflattened device tree

There are several places in the tree that read in a dtb file
and unflatten it. Add a of_read_file() helper function for that
and use it where appropriately.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 33 insertions, 10 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 5644e8e953..5da1881155 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -17,6 +17,7 @@
 #include <linux/sizes.h>
 #include <of_graph.h>
 #include <string.h>
+#include <libfile.h>
 #include <linux/clk.h>
 #include <linux/ctype.h>
 #include <linux/err.h>
@@ -2893,6 +2894,37 @@ int of_device_disable_by_alias(const char *alias)
 }
 
 /**
+ * of_read_file - unflatten oftree file
+ * @filename - path to file to unflatten its contents
+ *
+ * Returns the root node of the tree or an error pointer on error.
+ */
+struct device_node *of_read_file(const char *filename)
+{
+	void *fdt;
+	size_t size;
+	struct device_node *root;
+
+	fdt = read_file(filename, &size);
+	if (!fdt) {
+		pr_err("unable to read %s: %m\n", filename);
+		return ERR_PTR(-errno);
+	}
+
+	if (IS_ENABLED(CONFIG_FILETYPE) && file_detect_type(fdt, size) != filetype_oftree) {
+		pr_err("%s is not a flat device tree file.\n", filename);
+		root = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	root = of_unflatten_dtb(fdt, size);
+out:
+	free(fdt);
+
+	return root;
+}
+
+/**
  * of_get_reproducible_name() - get a reproducible name of a node
  * @node: The node to get a name from
  *
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 9d112b67f1..223ebb318b 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -308,22 +308,13 @@ static bool of_overlay_matches_filter(const char *filename, struct device_node *
 int of_overlay_apply_file(struct device_node *root, const char *filename,
 			  bool filter)
 {
-	void *fdt;
 	struct device_node *ovl;
-	size_t size;
 	int ret;
 
 	if (filter && !of_overlay_matches_filter(filename, NULL))
 		return 0;
 
-	ret = read_file_2(filename, &size, &fdt, FILESIZE_MAX);
-	if (ret)
-		return ret;
-
-	ovl = of_unflatten_dtb(fdt, size);
-
-	free(fdt);
-
+	ovl = of_read_file(filename);
 	if (IS_ERR(ovl)) {
 		pr_err("Failed to unflatten %s: %pe\n", filename, ovl);
 		return PTR_ERR(ovl);