kernel: backport mtd implementation for "compatible" in "partitions" subnode

This backports upstream support for "compatible" DT property set for the
"partitions" subnode of flash node. It allows specifying how partitions
should be created/parsed. Right now only "fixed-partitions" is
supported.

It should eventually replace our downstream "linux,part-probe" solution.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

1 files changed, 121 insertions, 0 deletions

diff --git a/target/linux/generic/backport-4.9/066-v4.16-0001-mtd-partitions-add-of_match_table-parser-matching.patch b/target/linux/generic/backport-4.9/066-v4.16-0001-mtd-partitions-add-of_match_table-parser-matching.patch
new file mode 100644
index 0000000000..06931ce2a4
--- /dev/null
+++ b/target/linux/generic/backport-4.9/066-v4.16-0001-mtd-partitions-add-of_match_table-parser-matching.patch
@@ -0,0 +1,121 @@
+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
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+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);