[PATCH 0/3] commands: findmnt: add option to print kernel root option

[PATCH 0/3] commands: findmnt: add option to print kernel root option

[Ahmad Fatoum]

There exists currently no way to view the kernel root option that
barebox would generate when instructed to via global.bootm.root_dev,
but without actually mounting the file system.

Add a new -K option that can print this. This can be useful in scripts
that want to fixup the root line, so it's interpreted by the rdinit, but
not by the kernel.

This applies on top of 
https://lore.barebox.org/barebox/20250401104806.3959859-1-a.fatoum@pengutronix.de/T/#t

Ahmad Fatoum (3):
  commands: devlookup: factor out cmd_export_val
  commands: findmnt: add support for exporting target as variable
  commands: findmnt: add option to print kernel root option

 commands/Kconfig     |  4 +++-
 commands/devlookup.c | 16 ++-----------
 commands/findmnt.c   | 56 +++++++++++++++++++++++++++++++++++++-------
 common/command.c     | 13 ++++++++++
 include/command.h    |  2 ++
 5 files changed, 68 insertions(+), 23 deletions(-)

-- 
2.39.5

[PATCH 1/3] commands: devlookup: factor out cmd_export_val

[Ahmad Fatoum]

Until we have support for capturing command output into a variable,
future commands will continue to have a -v parameter or similar for
printing the output of a command into a variable.

Add a helper for this that either prints it to the variable or to
stdout. This will allow easy migration to command output capture once we
have it.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 commands/devlookup.c | 16 ++--------------
 common/command.c     | 13 +++++++++++++
 include/command.h    |  2 ++
 3 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/commands/devlookup.c b/commands/devlookup.c
index bc9bd9461443..4a2c9b773661 100644
--- a/commands/devlookup.c
+++ b/commands/devlookup.c
@@ -9,18 +9,6 @@
 #include <linux/ctype.h>
 #include <environment.h>
 
-static int report(const char *variable, const char *val)
-{
-	if (!val)
-		return -(errno ?: EINVAL);
-
-	if (variable)
-		return setenv(variable, val);
-
-	printf("%s\n", val);
-	return 0;
-}
-
 static int do_devlookup(int argc, char *argv[])
 {
 	const char *variable = NULL, *devicefile, *paramname;
@@ -56,9 +44,9 @@ static int do_devlookup(int argc, char *argv[])
 	}
 
 	if (paramname)
-		ret = report(variable, dev_get_param(cdev->dev, paramname));
+		ret = cmd_export_val(variable, dev_get_param(cdev->dev, paramname));
 	else
-		ret = report(variable, dev_name(cdev->dev));
+		ret = cmd_export_val(variable, dev_name(cdev->dev));
 out:
 	cdev_close(cdev);
 
diff --git a/common/command.c b/common/command.c
index 014b85f9a35f..a119b0f41b3a 100644
--- a/common/command.c
+++ b/common/command.c
@@ -128,6 +128,19 @@ struct command *find_cmd (const char *cmd)
 }
 EXPORT_SYMBOL(find_cmd);
 
+int cmd_export_val(const char *variable, const char *val)
+{
+	if (!val)
+		return -EINVAL;
+
+	if (variable)
+		return setenv(variable, val);
+
+	printf("%s\n", val);
+	return 0;
+}
+EXPORT_SYMBOL(cmd_export_val);
+
 /*
  * Put all commands into a linked list. Without module support we could use
  * the raw command array, but with module support a list is easier to handle.
diff --git a/include/command.h b/include/command.h
index 26e06077b071..03ac270d1305 100644
--- a/include/command.h
+++ b/include/command.h
@@ -52,6 +52,7 @@ extern struct command * const __barebox_cmd_end[];
 /* common/command.c */
 #ifdef CONFIG_COMMAND_SUPPORT
 struct command *find_cmd(const char *cmd);
+int cmd_export_val(const char *variable, const char *val);
 int execute_command(int argc, char **argv);
 void barebox_cmd_usage(struct command *cmdtp);
 int run_command(const char *cmd);
@@ -59,6 +60,7 @@ int run_command(const char *cmd);
 static inline struct command *find_cmd(const char *cmd) { return NULL; }
 static inline int execute_command(int argc, char **argv) { return -ENOSYS; }
 static inline void barebox_cmd_usage(struct command *cmdtp) {}
+static inline int cmd_export_val(const char *variable, const char *val) { return -ENOSYS; }
 static inline int run_command(const char *cmd) { return -ENOSYS; }
 #endif
 
-- 
2.39.5

[PATCH 2/3] commands: findmnt: add support for exporting target as variable

[Ahmad Fatoum]

This can be useful information in a script, so let's allow exporting it
into a variable.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 commands/Kconfig   |  3 ++-
 commands/findmnt.c | 31 ++++++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/commands/Kconfig b/commands/Kconfig
index 313910d6649b..f36dcf02a8ea 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -690,7 +690,7 @@ config CMD_FINDMNT
 	help
 	  Find a file system
 
-	  Usage: findmnt [ DEVICE | -T FILE ]
+	  Usage: findmnt [ DEVICE | -T FILE ] [-v VARIABLE]
 
 	  findmnt will list all mounted filesystems or search
 	  for a filesystem when given the mountpoint or the
@@ -698,6 +698,7 @@ config CMD_FINDMNT
 
 	  Options:
 		-T		mount target file path
+		-v VARIABLE	export target to specified VARIABLE
 
 config CMD_PARTED
 	tristate
diff --git a/commands/findmnt.c b/commands/findmnt.c
index 3c9a520b8500..c64ef8760684 100644
--- a/commands/findmnt.c
+++ b/commands/findmnt.c
@@ -15,12 +15,18 @@ static void print_header(bool *header_printed)
 	*header_printed = true;
 }
 
-static void report_findmnt(const struct fs_device *fsdev)
+static void report_findmnt(const struct fs_device *fsdev,
+			   const char *variable)
 {
 	const char *backingstore;
 
 	backingstore = fsdev->backingstore ?: cdev_name(fsdev->cdev) ?: "none";
 
+	if (variable) {
+		cmd_export_val(variable, backingstore);
+		return;
+	}
+
 	printf("%-20s%-25s%-10s%-20s\n", fsdev->path, backingstore,
 	       fsdev->driver->drv.name, fsdev->options);
 }
@@ -31,9 +37,13 @@ static int do_findmnt(int argc, char *argv[])
 	struct fs_device *target = NULL;
 	char *device = NULL;
 	int opt, dirfd = AT_FDCWD;
+	const char *variable = NULL;
 
-	while ((opt = getopt(argc, argv, "T:")) > 0) {
+	while ((opt = getopt(argc, argv, "T:v:")) > 0) {
 		switch(opt) {
+		case 'v':
+			variable = optarg;
+			break;
 		case 'T':
 			target = get_fsdevice_by_path(dirfd, optarg);
 			if (!target)
@@ -50,9 +60,12 @@ static int do_findmnt(int argc, char *argv[])
 	if ((target && argc > 0) || (!target && argc > 1))
 		return COMMAND_ERROR_USAGE;
 
+	if (variable)
+		header_printed = true;
+
 	if (target) {
 		print_header(&header_printed);
-		report_findmnt(target);
+		report_findmnt(target, variable);
 		return 0;
 	}
 
@@ -60,13 +73,16 @@ static int do_findmnt(int argc, char *argv[])
 		device = canonicalize_path(dirfd, argv[0]);
 		if (!device)
 			return COMMAND_ERROR;
+	} else if (variable) {
+		return COMMAND_ERROR_USAGE;
 	}
 
 	for_each_fs_device(target) {
 		if (!device || streq_ptr(target->path, device) ||
 		    streq_ptr(target->backingstore, device)) {
-			print_header(&header_printed);
-			report_findmnt(target);
+			if (!variable)
+				print_header(&header_printed);
+			report_findmnt(target, variable);
 		} else {
 			const char *backingstore;
 			struct cdev *cdev;
@@ -80,7 +96,7 @@ static int do_findmnt(int argc, char *argv[])
 
 			if (streq_ptr(backingstore, cdev->name)) {
 				print_header(&header_printed);
-				report_findmnt(target);
+				report_findmnt(target, variable);
 			}
 			cdev_close(cdev);
 		}
@@ -98,12 +114,13 @@ BAREBOX_CMD_HELP_TEXT("source device as an argument")
 BAREBOX_CMD_HELP_TEXT("")
 BAREBOX_CMD_HELP_TEXT("Options:")
 BAREBOX_CMD_HELP_OPT ("-T",  "mount target file path")
+BAREBOX_CMD_HELP_OPT ("-v VARIABLE",  "export target to specified VARIABLE")
 BAREBOX_CMD_HELP_END
 
 BAREBOX_CMD_START(findmnt)
 	.cmd		= do_findmnt,
 	BAREBOX_CMD_DESC("find a file system")
-	BAREBOX_CMD_OPTS("[ DEVICE | -T FILE ]")
+	BAREBOX_CMD_OPTS("[ DEVICE | -T FILE ] [-v VAR]")
 	BAREBOX_CMD_GROUP(CMD_GRP_FILE)
 	BAREBOX_CMD_HELP(cmd_findmnt_help)
 BAREBOX_CMD_END
-- 
2.39.5

[PATCH 3/3] commands: findmnt: add option to print kernel root option

[Ahmad Fatoum]

There exists currently no way to view the kernel root option that
barebox would generate when instructed to via global.bootm.root_dev,
but without actually mounting the file system.

Add a new -K option that can print this. This can be useful in scripts
that want to fixup the root line, so it's interpreted by the rdinit, but
not by the kernel.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 commands/Kconfig   |  3 ++-
 commands/findmnt.c | 29 ++++++++++++++++++++++++++---
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/commands/Kconfig b/commands/Kconfig
index f36dcf02a8ea..58e0a8b0bfe4 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -690,7 +690,7 @@ config CMD_FINDMNT
 	help
 	  Find a file system
 
-	  Usage: findmnt [ DEVICE | -T FILE ] [-v VARIABLE]
+	  Usage: findmnt [-K] [ DEVICE | -T FILE ] [-v VARIABLE]
 
 	  findmnt will list all mounted filesystems or search
 	  for a filesystem when given the mountpoint or the
@@ -699,6 +699,7 @@ config CMD_FINDMNT
 	  Options:
 		-T		mount target file path
 		-v VARIABLE	export target to specified VARIABLE
+		-K		output kernel rootarg line
 
 config CMD_PARTED
 	tristate
diff --git a/commands/findmnt.c b/commands/findmnt.c
index c64ef8760684..21868fcc0e56 100644
--- a/commands/findmnt.c
+++ b/commands/findmnt.c
@@ -6,6 +6,7 @@
 #include <fs.h>
 #include <errno.h>
 #include <getopt.h>
+#include <block.h>
 
 static void print_header(bool *header_printed)
 {
@@ -38,9 +39,13 @@ static int do_findmnt(int argc, char *argv[])
 	char *device = NULL;
 	int opt, dirfd = AT_FDCWD;
 	const char *variable = NULL;
+	bool kernelopt = false;
 
-	while ((opt = getopt(argc, argv, "T:v:")) > 0) {
+	while ((opt = getopt(argc, argv, "KT:v:")) > 0) {
 		switch(opt) {
+		case 'K':
+			kernelopt = true;
+			break;
 		case 'v':
 			variable = optarg;
 			break;
@@ -57,7 +62,8 @@ static int do_findmnt(int argc, char *argv[])
 	argv += optind;
 	argc -= optind;
 
-	if ((target && argc > 0) || (!target && argc > 1))
+	if ((target && argc > 0) || (!target && argc > 1) ||
+	    (target && kernelopt) || (kernelopt && argc != 1))
 		return COMMAND_ERROR_USAGE;
 
 	if (variable)
@@ -77,6 +83,22 @@ static int do_findmnt(int argc, char *argv[])
 		return COMMAND_ERROR_USAGE;
 	}
 
+	if (kernelopt) {
+		struct cdev *cdev;
+		char *root_arg;
+		int ret;
+
+		cdev = cdev_open_by_name(device, O_RDONLY);
+		if (!cdev)
+			return COMMAND_ERROR;;
+
+		root_arg = cdev_get_linux_rootarg(cdev);
+		ret = cmd_export_val(variable, root_arg);
+		free(root_arg);
+
+		return ret;
+	}
+
 	for_each_fs_device(target) {
 		if (!device || streq_ptr(target->path, device) ||
 		    streq_ptr(target->backingstore, device)) {
@@ -115,12 +137,13 @@ BAREBOX_CMD_HELP_TEXT("")
 BAREBOX_CMD_HELP_TEXT("Options:")
 BAREBOX_CMD_HELP_OPT ("-T",  "mount target file path")
 BAREBOX_CMD_HELP_OPT ("-v VARIABLE",  "export target to specified VARIABLE")
+BAREBOX_CMD_HELP_OPT ("-K",  "output kernel rootarg line")
 BAREBOX_CMD_HELP_END
 
 BAREBOX_CMD_START(findmnt)
 	.cmd		= do_findmnt,
 	BAREBOX_CMD_DESC("find a file system")
-	BAREBOX_CMD_OPTS("[ DEVICE | -T FILE ] [-v VAR]")
+	BAREBOX_CMD_OPTS("[-K] [ DEVICE | -T FILE ] [-v VAR]")
 	BAREBOX_CMD_GROUP(CMD_GRP_FILE)
 	BAREBOX_CMD_HELP(cmd_findmnt_help)
 BAREBOX_CMD_END
-- 
2.39.5