[PATCH v2 7/7] commands: dmsetup: Basic command set for dm device management

[Tobias Waldekranz <tobias@waldekranz.com>]

Modeled on dmsetup(8) from LVM2.

This lets the user create/remove arbitrary dm devices using the same
table file format used in Linux, and dump information about currently
configured devices.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
---

Notes:
    v1 -> v2:
    - Use plain stdio over logged output
    - Make proper use of printk() format specifiers

 commands/Kconfig   |  14 +++++
 commands/Makefile  |   1 +
 commands/dmsetup.c | 144 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 159 insertions(+)
 create mode 100644 commands/dmsetup.c

diff --git a/commands/Kconfig b/commands/Kconfig
index 1626912c30..219f626c3e 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -732,6 +732,20 @@ config CMD_PARTED
 	         unit <unit>     change display/input units
 	         refresh         refresh a partition table
 
+config CMD_DMSETUP
+	tristate
+	depends on DM_BLK
+	prompt "dmsetup"
+	help
+	  dmsetup - low level interface to the device mapper
+
+	  Compose virtual block devices from a table of mappings from
+	  logical block addresses to various data sources, such as
+	  linear ranges from other existing devices.
+
+	  commands:
+	        create <name> <table-file>
+
 config CMD_UBI
 	tristate
 	default y if MTD_UBI
diff --git a/commands/Makefile b/commands/Makefile
index d9403b18d5..6b010fe30c 100644
--- a/commands/Makefile
+++ b/commands/Makefile
@@ -166,4 +166,5 @@ obj-$(CONFIG_CMD_STACKSMASH)	+= stacksmash.o
 obj-$(CONFIG_CMD_PARTED)	+= parted.o
 obj-$(CONFIG_CMD_EFI_HANDLE_DUMP)	+= efi_handle_dump.o
 obj-$(CONFIG_CMD_HOST)		+= host.o
+obj-$(CONFIG_CMD_DMSETUP)	+= dmsetup.o
 UBSAN_SANITIZE_ubsan.o := y
diff --git a/commands/dmsetup.c b/commands/dmsetup.c
new file mode 100644
index 0000000000..8900d5b85c
--- /dev/null
+++ b/commands/dmsetup.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// SPDX-FileCopyrightText: © 2025 Tobias Waldekranz <tobias@waldekranz.com>, Wires
+
+#include <command.h>
+#include <device-mapper.h>
+#include <libfile.h>
+#include <stdio.h>
+
+static struct dm_device *dmsetup_find(const char *name)
+{
+	struct dm_device *dm;
+
+	dm = dm_find_by_name(name);
+	if (IS_ERR_OR_NULL(dm)) {
+		printf("Found no device named \"%s\"\n", name);
+		return NULL;
+	}
+
+	return dm;
+}
+
+static int dmsetup_remove(int argc, char *argv[])
+{
+	struct dm_device *dm;
+
+	if (argc != 1)
+		return COMMAND_ERROR_USAGE;
+
+	dm = dmsetup_find(argv[0]);
+	if (!dm)
+		return COMMAND_ERROR;
+
+	dm_destroy(dm);
+
+	printf("Removed %s\n", argv[0]);
+	return COMMAND_SUCCESS;
+}
+
+static int dmsetup_info_one(struct dm_device *dm, void *_n)
+{
+	int *n = _n;
+	char *str;
+
+	if (*n)
+		putchar('\n');
+
+	str = dm_asprint(dm);
+	puts(str);
+	free(str);
+	(*n)++;
+	return 0;
+}
+
+static int dmsetup_info(int argc, char *argv[])
+{
+	struct dm_device *dm;
+	int n = 0;
+
+	if (argc == 0) {
+		dm_foreach(dmsetup_info_one, &n);
+		if (n == 0)
+			printf("No devices found\n");
+		return COMMAND_SUCCESS;
+	}
+
+	if (argc != 1)
+		return COMMAND_ERROR_USAGE;
+
+	dm = dmsetup_find(argv[0]);
+	if (!dm)
+		return COMMAND_ERROR;
+
+	dmsetup_info_one(dm, &n);
+	return COMMAND_SUCCESS;
+}
+
+
+static int dmsetup_create(int argc, char *argv[])
+{
+	struct dm_device *dm;
+	char *table;
+
+	if (argc != 2)
+		return COMMAND_ERROR_USAGE;
+
+	table = read_file(argv[1], NULL);
+	if (!table) {
+		printf("Failed to read table from %s: %m\n", argv[1]);
+		return COMMAND_ERROR;
+	}
+
+	dm = dm_create(argv[0], table);
+	free(table);
+	if (IS_ERR_OR_NULL(dm)) {
+		printf("Failed to create %s: %pe\n", argv[0], dm);
+		return COMMAND_ERROR;
+	}
+
+	printf("Created %s\n", argv[0]);
+	return COMMAND_SUCCESS;
+}
+
+static int do_dmsetup(int argc, char *argv[])
+{
+	const char *cmd;
+
+	if (argc < 2)
+		return COMMAND_ERROR_USAGE;
+
+	cmd = argv[1];
+	argc -= 2;
+	argv += 2;
+
+	if (!strcmp(cmd, "create"))
+		return dmsetup_create(argc, argv);
+	else if (!strcmp(cmd, "info"))
+		return dmsetup_info(argc, argv);
+	else if (!strcmp(cmd, "remove"))
+		return dmsetup_remove(argc, argv);
+
+	printf("Unknown command: %s\n", cmd);
+	return -EINVAL;
+}
+
+BAREBOX_CMD_HELP_START(dmsetup)
+BAREBOX_CMD_HELP_TEXT("dmsetup - low level interface to the device mapper")
+BAREBOX_CMD_HELP_TEXT("")
+BAREBOX_CMD_HELP_TEXT("Compose virtual block devices from a table of mappings from")
+BAREBOX_CMD_HELP_TEXT("logical block addresses to various data sources, such as")
+BAREBOX_CMD_HELP_TEXT("linear ranges from other existing devices.")
+BAREBOX_CMD_HELP_TEXT("")
+BAREBOX_CMD_HELP_TEXT("commands:")
+BAREBOX_CMD_HELP_OPT("create <name> <table-file>", "Create new device")
+BAREBOX_CMD_HELP_OPT("info [<name>]", "Show device information")
+BAREBOX_CMD_HELP_OPT("remove <name>", "Remove device")
+BAREBOX_CMD_HELP_END
+
+BAREBOX_CMD_START(dmsetup)
+	.cmd = do_dmsetup,
+	BAREBOX_CMD_DESC("low level interface to the device mapper")
+	BAREBOX_CMD_OPTS("<command> [args...]")
+	BAREBOX_CMD_GROUP(CMD_GRP_PART)
+	BAREBOX_CMD_HELP(cmd_dmsetup_help)
+BAREBOX_CMD_END
-- 
2.43.0