From b0321721be50b80c03a51866a94fde4f94690e18 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
Date: Wed, 15 Jun 2022 21:42:59 +0200
Subject: [PATCH] mtd: allow getting MTD device associated with a specific DT
 node
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MTD subsystem API allows interacting with MTD devices (e.g. reading,
writing, handling bad blocks). So far a random driver could get MTD
device only by its name (get_mtd_device_nm()). This change allows
getting them also by a DT node.

This API is required for drivers handling DT defined MTD partitions in a
specific way (e.g. U-Boot (sub)partition with environment variables).

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/mtd/mtdcore.c   | 28 ++++++++++++++++++++++++++++
 include/linux/mtd/mtd.h |  1 +
 2 files changed, 29 insertions(+)

--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1236,6 +1236,34 @@ int __get_mtd_device(struct mtd_info *mt
 EXPORT_SYMBOL_GPL(__get_mtd_device);
 
 /**
+ * of_get_mtd_device_by_node - obtain an MTD device associated with a given node
+ *
+ * @np: device tree node
+ */
+struct mtd_info *of_get_mtd_device_by_node(struct device_node *np)
+{
+	struct mtd_info *mtd = NULL;
+	struct mtd_info *tmp;
+	int err;
+
+	mutex_lock(&mtd_table_mutex);
+
+	err = -EPROBE_DEFER;
+	mtd_for_each_device(tmp) {
+		if (mtd_get_of_node(tmp) == np) {
+			mtd = tmp;
+			err = __get_mtd_device(mtd);
+			break;
+		}
+	}
+
+	mutex_unlock(&mtd_table_mutex);
+
+	return err ? ERR_PTR(err) : mtd;
+}
+EXPORT_SYMBOL_GPL(of_get_mtd_device_by_node);
+
+/**
  *	get_mtd_device_nm - obtain a validated handle for an MTD device by
  *	device name
  *	@name: MTD device name to open
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -682,6 +682,7 @@ extern int mtd_device_unregister(struct
 extern struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num);
 extern int __get_mtd_device(struct mtd_info *mtd);
 extern void __put_mtd_device(struct mtd_info *mtd);
+extern struct mtd_info *of_get_mtd_device_by_node(struct device_node *np);
 extern struct mtd_info *get_mtd_device_nm(const char *name);
 extern void put_mtd_device(struct mtd_info *mtd);
 
