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From:   =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <zajec5@gmail.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>
Cc:     Tom Rini <trini@konsulko.com>,
        Ahmad Fatoum <a.fatoum@pengutronix.de>,
        linux-arm-kernel@lists.infradead.org, u-boot@lists.denx.de,
        devicetree@vger.kernel.org, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org,
        =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
Subject: [PATCH V4 1/2] mtd: allow getting MTD device associated with a specific DT node
Date:   Wed, 15 Jun 2022 21:42:59 +0200
Message-Id: <20220615194300.13358-1-zajec5@gmail.com>
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From: Rafał Miłecki <rafal@milecki.pl>

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>
---
V3: First introduction of of_get_mtd_device_by_node()
V4: Use EPROBE_DEFER

Srinivas: in V3 Miquel said it's OK to push this patch through NVMEM 
---
 drivers/mtd/mtdcore.c   | 28 ++++++++++++++++++++++++++++
 include/linux/mtd/mtd.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 9eb0680db312..3613cc142f25 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1154,6 +1154,34 @@ int __get_mtd_device(struct mtd_info *mtd)
 }
 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
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 955aee14b0f7..6fc841ceef31 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -677,6 +677,7 @@ extern int mtd_device_unregister(struct mtd_info *master);
 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);
 
-- 
2.34.1