linux-kernel - [PATCH v4 2/2] mtd: core: introduce of support for dynamic partitions

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Message-Id: <20220518233258.5483-3-ansuelsmth@gmail.com>
Date:   Thu, 19 May 2022 01:32:58 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Ansuel Smith <ansuelsmth@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/2] mtd: core: introduce of support for dynamic partitions

We have many parser that register mtd partitions at runtime. One example
is the cmdlinepart or the smem-part parser where the compatible is defined
in the dts and the partitions gets detected and registered by the
parser. This is problematic for the NVMEM subsystem that requires an OF node
to detect NVMEM cells.

To fix this problem, introduce an additional logic that will try to
assign an OF node to the MTD if declared.

On MTD addition, it will be checked if the MTD has an OF node and if
not declared will check if a partition with the same label is
declared in DTS. If an exact match is found, the partition dynamically
allocated by the parser will have a connected OF node.

The NVMEM subsystem will detect the OF node and register any NVMEM cells
declared statically in the DTS.

Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
---
 drivers/mtd/mtdcore.c | 49 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 7731796024e0..807194efb580 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -546,6 +546,54 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
 	return 0;
 }
 
+static void mtd_check_of_node(struct mtd_info *mtd)
+{
+	struct device_node *partitions, *parent_dn, *mtd_dn = NULL;
+	struct mtd_info *parent;
+	const char *mtd_name;
+	bool found = false;
+	int plen;
+
+	/* Check if MTD already has a device node */
+	if (dev_of_node(&mtd->dev))
+		return;
+
+	/* Check if a partitions node exist */
+	parent = mtd->parent;
+	parent_dn = dev_of_node(&parent->dev);
+	if (!parent_dn)
+		return;
+
+	partitions = of_get_child_by_name(parent_dn, "partitions");
+	if (!partitions)
+		goto exit_parent;
+
+	/* Search if a partition is defined with the same name */
+	for_each_child_of_node(partitions, mtd_dn) {
+		/* Skip partition with no label */
+		mtd_name = of_get_property(mtd_dn, "label", &plen);
+		if (!mtd_name)
+			continue;
+
+		if (!strncmp(mtd->name, mtd_name, plen)) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found)
+		goto exit_partitions;
+
+	/* Set of_node only for nvmem */
+	if (of_device_is_compatible(mtd_dn, "nvmem-cells"))
+		mtd_set_of_node(mtd, mtd_dn);
+
+exit_partitions:
+	of_node_put(partitions);
+exit_parent:
+	of_node_put(parent_dn);
+}
+
 /**
  *	add_mtd_device - register an MTD device
  *	@mtd: pointer to new MTD device info structure
@@ -651,6 +699,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	mtd->dev.devt = MTD_DEVT(i);
 	dev_set_name(&mtd->dev, "mtd%d", i);
 	dev_set_drvdata(&mtd->dev, mtd);
+	mtd_check_of_node(mtd);
 	of_node_get(mtd_get_of_node(mtd));
 	error = device_register(&mtd->dev);
 	if (error)
-- 
2.34.1