From: Felix Fietkau <nbd@nbd.name>
Subject: make rootfs split/detection more generic - patch can be moved to generic-2.6 after testing on other platforms

lede-commit: 328e660b31f0937d52c5ae3d6e7029409918a9df
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/mtd/Kconfig            | 17 +++++++++++++++++
 drivers/mtd/mtdpart.c          | 35 +++++++++++++++++++++++++++++++++++
 include/linux/mtd/partitions.h |  2 ++
 3 files changed, 54 insertions(+)

--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -12,6 +12,23 @@ menuconfig MTD
 
 if MTD
 
+menu "OpenWrt specific MTD options"
+
+config MTD_ROOTFS_ROOT_DEV
+	bool "Automatically set 'rootfs' partition to be root filesystem"
+	default y
+
+config MTD_SPLIT_FIRMWARE
+	bool "Automatically split firmware partition for kernel+rootfs"
+	default y
+
+config MTD_SPLIT_FIRMWARE_NAME
+	string "Firmware partition name"
+	depends on MTD_SPLIT_FIRMWARE
+	default "firmware"
+
+endmenu
+
 config MTD_TESTS
 	tristate "MTD tests support (DANGEROUS)"
 	depends on m
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -29,10 +29,12 @@
 #include <linux/kmod.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
+#include <linux/magic.h>
 #include <linux/of.h>
 #include <linux/err.h>
 
 #include "mtdcore.h"
+#include "mtdsplit/mtdsplit.h"
 
 /* Our partition linked list */
 static LIST_HEAD(mtd_partitions);
@@ -52,6 +54,8 @@ struct mtd_part {
 	struct list_head list;
 };
 
+static void mtd_partition_split(struct mtd_info *master, struct mtd_part *part);
+
 /*
  * Given a pointer to the MTD object in the mtd_part structure, we can retrieve
  * the pointer to that structure.
@@ -678,6 +682,7 @@ int mtd_add_partition(struct mtd_info *p
 	mutex_unlock(&mtd_partitions_mutex);
 
 	add_mtd_device(&new->mtd);
+	mtd_partition_split(parent, new);
 
 	mtd_add_partition_attrs(new);
 
@@ -756,6 +761,35 @@ int mtd_del_partition(struct mtd_info *m
 }
 EXPORT_SYMBOL_GPL(mtd_del_partition);
 
+#ifdef CONFIG_MTD_SPLIT_FIRMWARE_NAME
+#define SPLIT_FIRMWARE_NAME	CONFIG_MTD_SPLIT_FIRMWARE_NAME
+#else
+#define SPLIT_FIRMWARE_NAME	"unused"
+#endif
+
+static void split_firmware(struct mtd_info *master, struct mtd_part *part)
+{
+}
+
+void __weak arch_split_mtd_part(struct mtd_info *master, const char *name,
+                                int offset, int size)
+{
+}
+
+static void mtd_partition_split(struct mtd_info *master, struct mtd_part *part)
+{
+	static int rootfs_found = 0;
+
+	if (rootfs_found)
+		return;
+
+	if (!strcmp(part->mtd.name, SPLIT_FIRMWARE_NAME) &&
+	    IS_ENABLED(CONFIG_MTD_SPLIT_FIRMWARE))
+		split_firmware(master, part);
+
+	arch_split_mtd_part(master, part->mtd.name, part->offset,
+			    part->mtd.size);
+}
 /*
  * This function, given a master MTD object and a partition table, creates
  * and registers slave MTD objects which are bound to the master according to
@@ -787,6 +821,7 @@ int add_mtd_partitions(struct mtd_info *
 		mutex_unlock(&mtd_partitions_mutex);
 
 		add_mtd_device(&slave->mtd);
+		mtd_partition_split(master, slave);
 		mtd_add_partition_attrs(slave);
 		if (parts[i].types)
 			mtd_parse_part(slave, parts[i].types);
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -109,5 +109,7 @@ int mtd_add_partition(struct mtd_info *m
 		      long long offset, long long length);
 int mtd_del_partition(struct mtd_info *master, int partno);
 uint64_t mtd_get_device_size(const struct mtd_info *mtd);
+extern void __weak arch_split_mtd_part(struct mtd_info *master,
+				       const char *name, int offset, int size);
 
 #endif