[PATCH V5 1/2] mtd: partitions: add of_match_table parser matching

Rafał Miłecki
2018-01-02T13:05:23Z

From: Brian Norris <computersforpeace@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@gmail.com>
Signed-off-by: Rafał Miłecki <rafal@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.
---
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..a3aaaa4af992 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;
+
+ 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