[PATCH V6 1/2] mtd: partitions: add of_match_table parser matching

[Rafał Miłecki]

From: Brian Norris <computersforpeace at gmail.com>

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 at gmail.com>
Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
This is based on Brian's patches:
[RFC PATCH 4/7] mtd: add of_match_mtd_parser() and of_mtd_match_mtd_parser() helpers
[RFC PATCH 6/7] RFC: mtd: partitions: enable of_match_table matching

V1: Put helpers in mtdpart.c instead of drivers/of/of_mtd.c
    Merge helpers into a single of_mtd_match_mtd_parser
V3: Add a simple comment to note we will need the best match in the future
V4: Rework new functions to pick parser with the best match
    Move new code in parse_mtd_partitions up so it has precedence over flash
    driver defaults and MTD defaults
V5: Rework matching code to start checking with the most specific string in the
    "compatibility" property.
V6: Initialize "ret" variable in mtd_part_get_parser_by_cp to NULL
---
 drivers/mtd/mtdpart.c          | 64 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/mtd/partitions.h |  1 +
 2 files changed, 65 insertions(+)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index be088bccd593..b11958adcf45 100644
--- 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"
 
@@ -880,6 +881,48 @@ static int mtd_part_do_parse(struct mtd_part_parser *parser,
 }
 
 /**
+ * mtd_part_get_parser_by_cp - find MTD parser by a compatible string
+ *
+ * @cp: 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_parser_by_cp(const char *cp)
+{
+	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->name[0] || matches->type[0] || matches->compatible[0];
+		     matches++) {
+			if (!matches->compatible[0])
+				continue;
+			if (!strcmp(matches->compatible, cp) &&
+			    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
@@ -905,8 +948,29 @@ int parse_mtd_partitions(struct mtd_info *master, const char *const *types,
 			 struct mtd_part_parser_data *data)
 {
 	struct mtd_part_parser *parser;
+	struct device_node *np;
+	struct property *prop;
+	const char *cp;
 	int ret, err = 0;
 
+	np = of_get_child_by_name(mtd_get_of_node(master), "partitions");
+	if (np) {
+		of_property_for_each_string(np, "compatible", prop, cp) {
+			parser = mtd_part_get_parser_by_cp(cp);
+			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;
 
diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index c4beb70dacbd..11cb0c50cd84 100644
--- 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);
-- 
2.11.0