From bb2192123ec70470d6ea33f138846b175403a968 Mon Sep 17 00:00:00 2001
From: Brian Norris <computersforpeace@gmail.com>
Date: Thu, 4 Jan 2018 08:05:33 +0100
Subject: [PATCH] mtd: partitions: add of_match_table parser matching
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Partition parsers can now provide an of_match_table to enable
flash<-->parser matching via device tree as documented in the
mtd/partition.txt.

It works by looking for a matching parser for every string in the
"compatibility" property (starting with the most specific one).

This support is currently limited to built-in parsers as it uses
request_module() and friends. This should be sufficient for most cases
though as compiling parsers as modules isn't a common choice.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/mtd/mtdpart.c          | 59 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/mtd/partitions.h |  1 +
 2 files changed, 60 insertions(+)

--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -30,6 +30,7 @@
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
 #include <linux/err.h>
+#include <linux/of.h>
 
 #include "mtdcore.h"
 
@@ -886,6 +887,45 @@ static int mtd_part_do_parse(struct mtd_
 }
 
 /**
+ * mtd_part_get_compatible_parser - find MTD parser by a compatible string
+ *
+ * @compat: compatible string describing partitions in a device tree
+ *
+ * MTD parsers can specify supported partitions by providing a table of
+ * compatibility strings. This function finds a parser that advertises support
+ * for a passed value of "compatible".
+ */
+static struct mtd_part_parser *mtd_part_get_compatible_parser(const char *compat)
+{
+	struct mtd_part_parser *p, *ret = NULL;
+
+	spin_lock(&part_parser_lock);
+
+	list_for_each_entry(p, &part_parsers, list) {
+		const struct of_device_id *matches;
+
+		matches = p->of_match_table;
+		if (!matches)
+			continue;
+
+		for (; matches->compatible[0]; matches++) {
+			if (!strcmp(matches->compatible, compat) &&
+			    try_module_get(p->owner)) {
+				ret = p;
+				break;
+			}
+		}
+
+		if (ret)
+			break;
+	}
+
+	spin_unlock(&part_parser_lock);
+
+	return ret;
+}
+
+/**
  * parse_mtd_partitions - parse MTD partitions
  * @master: the master partition (describes whole MTD device)
  * @types: names of partition parsers to try or %NULL
@@ -911,8 +951,27 @@ int parse_mtd_partitions(struct mtd_info
 			 struct mtd_part_parser_data *data)
 {
 	struct mtd_part_parser *parser;
+	struct device_node *np;
+	struct property *prop;
+	const char *compat;
 	int ret, err = 0;
 
+	np = of_get_child_by_name(mtd_get_of_node(master), "partitions");
+	of_property_for_each_string(np, "compatible", prop, compat) {
+		parser = mtd_part_get_compatible_parser(compat);
+		if (!parser)
+			continue;
+		ret = mtd_part_do_parse(parser, master, pparts, data);
+		if (ret > 0) {
+			of_node_put(np);
+			return 0;
+		}
+		mtd_part_parser_put(parser);
+		if (ret < 0 && !err)
+			err = ret;
+	}
+	of_node_put(np);
+
 	if (!types)
 		types = default_mtd_part_types;
 
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -77,6 +77,7 @@ struct mtd_part_parser {
 	struct list_head list;
 	struct module *owner;
 	const char *name;
+	const struct of_device_id *of_match_table;
 	int (*parse_fn)(struct mtd_info *, const struct mtd_partition **,
 			struct mtd_part_parser_data *);
 	void (*cleanup)(const struct mtd_partition *pparts, int nr_parts);