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From:   =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <zajec5@gmail.com>
To:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     Mikhail Zhilkin <csharper2005@gmail.com>,
        Christian Marangi <ansuelsmth@gmail.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        Jens Axboe <axboe@kernel.dk>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
Subject: [PATCH V2 2/2] mtd: core: set ROOT_DEV for partitions marked as rootfs in DT
Date:   Fri, 21 Oct 2022 08:00:51 +0200
Message-Id: <20221021060051.2508-2-zajec5@gmail.com>
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From: Rafał Miłecki <rafal@milecki.pl>

This adds support for "linux,rootfs" binding that is used to mark flash
partition containing rootfs. It's useful for devices using device tree
that don't have bootloader passing root info in cmdline.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
V2: Use "linux,rootfs" as more accurate. Thanks Rob.
---
 drivers/mtd/mtdcore.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 07249af4f890..034b06aff660 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -28,6 +28,7 @@
 #include <linux/leds.h>
 #include <linux/debugfs.h>
 #include <linux/nvmem-provider.h>
+#include <linux/root_dev.h>
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
@@ -735,6 +736,12 @@ int add_mtd_device(struct mtd_info *mtd)
 		not->add(mtd);
 
 	mutex_unlock(&mtd_table_mutex);
+
+	if (of_find_property(mtd_get_of_node(mtd), "linux,rootfs", NULL)) {
+		pr_info("mtd: setting mtd%d (%s) as root device\n", mtd->index, mtd->name);
+		ROOT_DEV = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
+	}
+
 	/* We _know_ we aren't being removed, because
 	   our caller is still holding us here. So none
 	   of this try_ nonsense, and no bitching about it
-- 
2.34.1