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Subject[PATCH v5 4/4] mtd: Add driver for concatenating devices
Date
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@nospam.obeliks.de>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
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@nospam.obeliks.de>
+ */
+
+#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@nospam.obeliks.de>");
+MODULE_DESCRIPTION("Virtual concat MTD device driver");
--
2.20.1
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