[PATCH 3/3] saveenv: provide a zeroed/empty/ignore environment

[Juergen Borleis]

If an external environment storage should be used in very rare and special cases,
the intentional behaviour should be to ignore the external environment and always
fall back to the built-in environment. By storing an empty "to be ignored" environment
into the external environment a confusing error message about invalid CRC sums will go
away and still the built-in environment is used.
With this new option we can force the intentional behaviour.

Signed-off-by: Juergen Borleis <jbe at pengutronix.de>
---
 commands/saveenv.c   | 30 ++++++++++++++++++++++--------
 scripts/bareboxenv.c | 10 ++++++++--
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/commands/saveenv.c b/commands/saveenv.c
index 41f111d..84ddfa7 100644
--- a/commands/saveenv.c
+++ b/commands/saveenv.c
@@ -18,26 +18,39 @@
 #include <common.h>
 #include <command.h>
 #include <errno.h>
+#include <getopt.h>
 #include <fs.h>
 #include <fcntl.h>
 #include <envfs.h>
 
 static int do_saveenv(int argc, char *argv[])
 {
-	int ret;
+	int ret, opt;
+	unsigned envfs_flags = 0;
 	char *filename, *dirname;
 
 	printf("saving environment\n");
-	if (argc < 3)
+	while ((opt = getopt(argc, argv, "z")) > 0) {
+		switch (opt) {
+		case 'z':
+			envfs_flags |= ENVFS_FLAGS_PLACEHOLDER;
+			break;
+		}
+	}
+
+	/* destination and source are given? */
+	if (argc == optind + 2)
+		dirname = argv[optind + 1];
+	else
 		dirname = "/env";
+
+	/* destination only given? */
+	if (argc == optind + 1)
+		filename = argv[optind];
 	else
-		dirname = argv[2];
-	if (argc < 2)
 		filename = default_environment_path_get();
-	else
-		filename = argv[1];
 
-	ret = envfs_save(filename, dirname, 0);
+	ret = envfs_save(filename, dirname, envfs_flags);
 
 	return ret;
 }
@@ -49,13 +62,14 @@ BAREBOX_CMD_HELP_TEXT("ENVFS is usually a block in flash but can be any other fi
 BAREBOX_CMD_HELP_TEXT("omitted, DIRECTORY defaults to /env and ENVFS defaults to")
 BAREBOX_CMD_HELP_TEXT("/dev/env0. Note that envfs can only handle files, directories are being")
 BAREBOX_CMD_HELP_TEXT("skipped silently.")
+BAREBOX_CMD_HELP_OPT ("-z",  "store a 'zeroed' environment to force the built-in default environment at startup")
 
 BAREBOX_CMD_HELP_END
 
 BAREBOX_CMD_START(saveenv)
 	.cmd		= do_saveenv,
 	BAREBOX_CMD_DESC("save environment to persistent storage")
-	BAREBOX_CMD_OPTS("[ENVFS] [DIRECTORY]")
+	BAREBOX_CMD_OPTS("[-z] [ENVFS [DIRECTORY]]")
 	BAREBOX_CMD_GROUP(CMD_GRP_ENV)
 	BAREBOX_CMD_HELP(cmd_saveenv_help)
 BAREBOX_CMD_END
diff --git a/scripts/bareboxenv.c b/scripts/bareboxenv.c
index ec6ccfe..1936155 100644
--- a/scripts/bareboxenv.c
+++ b/scripts/bareboxenv.c
@@ -109,6 +109,7 @@ static void usage(char *prgname)
 		"\n"
 		"options:\n"
 		"  -s        save (directory -> environment sector)\n"
+		"  -z        force the built-in default environment at startup\n"
 		"  -l        load (environment sector -> directory)\n"
 		"  -p <size> pad output file to given size\n"
 		"  -v        verbose\n",
@@ -120,9 +121,10 @@ int main(int argc, char *argv[])
 	int opt;
 	int save = 0, load = 0, pad = 0, err = 0, fd;
 	char *filename = NULL, *dirname = NULL;
+	unsigned envfs_flags = 0;
 	int verbose = 0;
 
-	while((opt = getopt(argc, argv, "slp:v")) != -1) {
+	while((opt = getopt(argc, argv, "slp:vz")) != -1) {
 		switch (opt) {
 		case 's':
 			save = 1;
@@ -133,6 +135,10 @@ int main(int argc, char *argv[])
 		case 'p':
 			pad = strtoul(optarg, NULL, 0);
 			break;
+		case 'z':
+			envfs_flags |= ENVFS_FLAGS_PLACEHOLDER;
+			save = 1;
+			break;
 		case 'v':
 			verbose = 1;
 			break;
@@ -181,7 +187,7 @@ int main(int argc, char *argv[])
 		if (verbose)
 			printf("saving contents of %s to file %s\n", dirname, filename);
 
-		err = envfs_save(filename, dirname, 0);
+		err = envfs_save(filename, dirname, envfs_flags);
 
 		if (verbose && err)
 			printf("saving env failed: %d\n", err);
-- 
2.0.1