[PATCH v5 4/4] mtd: Add driver for concatenating devices

[Miquel Raynal]

Introduce a generic way to define concatenated MTD devices. This may
be very useful in the case of ie. stacked SPI-NOR. Partitions to
concatenate are described in an additional property of the partitions
subnode:

        flash0 {
                partitions {
                        compatible = "fixed-partitions";
                        part-concat = <&flash0_part1>, <&flash1_part0>;

			part0@0 {
				label = "part0_0";
				reg = <0x0 0x800000>;
			};

			flash0_part1: part1@800000 {
				label = "part0_1";
				reg = <0x800000 0x800000>;
			};
                };
        };

        flash1 {
                partitions {
                        compatible = "fixed-partitions";

			flash0_part1: part1@0 {
				label = "part1_0";
				reg = <0x0 0x800000>;
			};

			part0@800000 {
				label = "part1_1";
				reg = <0x800000 0x800000>;
			};
                };
        };

This is useful for boards where memory range has been extended with
the use of multiple flash chips as memory banks of a single MTD
device, with partitions spanning chip borders.

Suggested-by: Bernhard Frauendienst <kernel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
 drivers/mtd/Kconfig           |   8 ++
 drivers/mtd/Makefile          |   1 +
 drivers/mtd/mtd_virt_concat.c | 240 ++++++++++++++++++++++++++++++++++
 3 files changed, 249 insertions(+)
 create mode 100644 drivers/mtd/mtd_virt_concat.c

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index 79a8ff542883..3e1e55e7158f 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -276,6 +276,14 @@ config MTD_PARTITIONED_MASTER
 	  the parent of the partition device be the master device, rather than
 	  what lies behind the master.
 
+config MTD_VIRT_CONCAT
+	tristate "Virtual concatenated MTD devices"
+	help
+	  This driver allows creation of a virtual MTD device, which
+	  concatenates multiple physical MTD devices into a single one.
+	  This is useful to create partitions bigger than the underlying
+	  physical chips by allowing cross-chip boundaries.
+
 source "drivers/mtd/chips/Kconfig"
 
 source "drivers/mtd/maps/Kconfig"
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 58fc327a5276..c7ee13368a66 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_SSFDC)		+= ssfdc.o
 obj-$(CONFIG_SM_FTL)		+= sm_ftl.o
 obj-$(CONFIG_MTD_OOPS)		+= mtdoops.o
 obj-$(CONFIG_MTD_SWAP)		+= mtdswap.o
+obj-$(CONFIG_MTD_VIRT_CONCAT)	+= mtd_virt_concat.o
 
 nftl-objs		:= nftlcore.o nftlmount.o
 inftl-objs		:= inftlcore.o inftlmount.o
diff --git a/drivers/mtd/mtd_virt_concat.c b/drivers/mtd/mtd_virt_concat.c
new file mode 100644
index 000000000000..23c7170ac32f
--- /dev/null
+++ b/drivers/mtd/mtd_virt_concat.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Virtual concat MTD device driver
+ *
+ * Copyright (C) 2018 Bernhard Frauendienst
+ * Author: Bernhard Frauendienst <kernel@xxxxxxxxxxxxxxxxx>
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/mtd/concat.h>
+#include <linux/mtd/mtd.h>
+#include "mtdcore.h"
+#include <linux/mtd/partitions.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+
+#define CONCAT_PROP "part-concat"
+#define MIN_DEV_PER_CONCAT 2
+
+/**
+ * struct mtd_virt_concat - concatenation container
+ * @vmtd: Virtual mtd_concat device
+ * @count: Number of physical underlaying devices in @devices
+ * @devices: Array of the physical devices used
+ */
+struct mtd_virt_concat {
+	struct mtd_info	*vmtd;
+	unsigned int count;
+	struct mtd_info	**devices;
+};
+
+/**
+ * struct mtd_virt_concat_node - components of a concatenation
+ * @head: List handle
+ * @count: Number of nodes
+ * @nodes: Pointer to the nodes (partitions) to concatenate
+ * @concat: Concatenation container
+ */
+struct mtd_virt_concat_node {
+	struct list_head head;
+	unsigned int count;
+	struct device_node **nodes;
+	struct mtd_virt_concat *concat;
+};
+
+static LIST_HEAD(concat_list);
+
+static void mtd_virt_concat_put_mtd_devices(struct mtd_virt_concat *concat)
+{
+	int i;
+
+	for (i = 0; i < concat->count; i++)
+		put_mtd_device(concat->devices[i]);
+}
+
+static int mtd_virt_concat_create_join(struct mtd_virt_concat_node *item)
+{
+	struct mtd_virt_concat *concat;
+	struct mtd_info *mtd;
+	ssize_t name_sz;
+	char *name;
+	int ret, i;
+
+	concat = kzalloc(sizeof(*concat), GFP_KERNEL);
+	if (!concat)
+		return -ENOMEM;
+
+	concat->devices = kcalloc(item->count,
+				  sizeof(*concat->devices),
+				  GFP_KERNEL);
+	if (!concat->devices) {
+		ret = -ENOMEM;
+		goto free_concat;
+	}
+
+	/* Aggregate the physical devices */
+	for (i = 0; i < item->count; i++) {
+		mtd = get_mtd_device_by_node(item->nodes[i]);
+		if (IS_ERR(mtd)) {
+			ret = PTR_ERR(mtd);
+			goto put_mtd_devices;
+		}
+
+		concat->devices[concat->count++] = mtd;
+	}
+
+	/* Create the virtual device */
+	name_sz = snprintf(NULL, 0, "%s-%s%s-concat",
+			   concat->devices[0]->name,
+			   concat->devices[1]->name,
+			   concat->count > 2 ? "-+" : "");
+	name = kmalloc(name_sz, GFP_KERNEL);
+	if (!name) {
+		ret = -ENOMEM;
+		goto put_mtd_devices;
+	}
+
+	sprintf(name, "%s-%s%s-concat",
+		concat->devices[0]->name,
+		concat->devices[1]->name,
+		concat->count > 2 ? "-+" : "");
+
+	concat->vmtd = mtd_concat_create(concat->devices, concat->count, name);
+	if (!concat->vmtd) {
+		ret = -ENXIO;
+		goto free_name;
+	}
+
+	/* Arbitrary set the first device as parent */
+	concat->vmtd->dev.parent = &concat->devices[0]->dev;
+
+	/* Register the platform device */
+	ret = mtd_device_register(concat->vmtd, NULL, 0);
+	if (ret)
+		goto destroy_concat;
+
+	item->concat = concat;
+
+	return 0;
+
+destroy_concat:
+	mtd_concat_destroy(concat->vmtd);
+free_name:
+	kfree(name);
+put_mtd_devices:
+	mtd_virt_concat_put_mtd_devices(concat);
+free_concat:
+	kfree(concat);
+
+	return ret;
+}
+
+static void mtd_virt_concat_destroy_joins(void)
+{
+	struct mtd_virt_concat_node *item, *tmp;
+
+	list_for_each_entry_safe(item, tmp, &concat_list, head) {
+		if (item->concat) {
+			mtd_device_unregister(item->concat->vmtd);
+			kfree(item->concat->vmtd->name);
+			mtd_concat_destroy(item->concat->vmtd);
+			mtd_virt_concat_put_mtd_devices(item->concat);
+		}
+	}
+}
+
+static int mtd_virt_concat_create_item(struct device_node *parts,
+				       unsigned int count)
+{
+	struct mtd_virt_concat_node *item;
+	int i;
+
+	item = kzalloc(sizeof(*item), GFP_KERNEL);
+	if (!item)
+		return -ENOMEM;
+
+	item->count = count;
+	item->nodes = kcalloc(count, sizeof(*item->nodes), GFP_KERNEL);
+	if (!item->nodes) {
+		kfree(item);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < count; i++)
+		item->nodes[i] = of_parse_phandle(parts, CONCAT_PROP, i);
+
+	list_add_tail(&item->head, &concat_list);
+
+	return 0;
+}
+
+static void mtd_virt_concat_destroy_items(void)
+{
+	struct mtd_virt_concat_node *item, *temp;
+	int i;
+
+	list_for_each_entry_safe(item, temp, &concat_list, head) {
+		for (i = 0; i < item->count; i++)
+			of_node_put(item->nodes[i]);
+
+		kfree(item->nodes);
+		kfree(item);
+	}
+}
+
+static int __init mtd_virt_concat_init(void)
+{
+	struct mtd_virt_concat_node *item;
+	struct device_node *parts = NULL;
+	int ret = 0, count;
+
+	/* List all the concatenations found in DT */
+	do {
+		parts = of_find_node_with_property(parts, CONCAT_PROP);
+		if (!of_device_is_available(parts))
+			continue;
+
+		count = of_count_phandle_with_args(parts, CONCAT_PROP, NULL);
+		if (count < MIN_DEV_PER_CONCAT)
+			continue;
+
+		ret = mtd_virt_concat_create_item(parts, count);
+		if (ret) {
+			of_node_put(parts);
+			goto destroy_items;
+		}
+	} while (parts);
+
+	/* TODO: also parse the cmdline */
+
+	/* Create the concatenations */
+	list_for_each_entry(item, &concat_list, head) {
+		ret = mtd_virt_concat_create_join(item);
+		if (ret)
+			goto destroy_joins;
+	}
+
+	return 0;
+
+destroy_joins:
+	mtd_virt_concat_destroy_joins();
+destroy_items:
+	mtd_virt_concat_destroy_items();
+
+	return ret;
+}
+late_initcall(mtd_virt_concat_init);
+
+static void __exit mtd_virt_concat_exit(void)
+{
+	mtd_virt_concat_destroy_joins();
+	mtd_virt_concat_destroy_items();
+}
+module_exit(mtd_virt_concat_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Bernhard Frauendienst <kernel@xxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Virtual concat MTD device driver");
-- 
2.20.1