tools/env: allow config filename to be passed via command line argument

When for example generating/manipulating SD card/eMMC images which
contain U-Boot and its environment(s), it is handy to use a given
configuration file instead of the compiled-in default one.
And since the default configuration file is expected under /etc
it's hard for an usual linux user account without special permissions
to use fw_printenv/fw_setenv for this purpose.
So allow to pass an optional filename via a new '-c' command
line argument.

Example:

$ ln -s fw_printenv tools/env/fw_setenv
$ cat fw_env.config
test.img 0x20000 0x20000
test.img 0x40000 0x20000

$ tools/env/fw_printenv -c ./fw_env.config fdt_file
fdt_file=imx28-duckbill.dtb

$ tools/env/fw_setenv -c ./fw_env.config fdt_file imx28-duckbill-spi.dtb

$ tools/env/fw_printenv -c ./fw_env.config fdt_file
fdt_file=imx28-duckbill-spi.dtb

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

tools/env/fw_env.c

@@ -124,6 +124,7 @@ static int parse_config (void);
 
 #if defined(CONFIG_FILE)
 static int get_config (char *);
+static char *config_file = CONFIG_FILE;
 #endif
 static inline ulong getenvsize (void)
 {
@@ -246,6 +247,19 @@ int fw_printenv (int argc, char *argv[])
 	int i, n_flag;
 	int rc = 0;
 
+#ifdef CONFIG_FILE
+	if (argc >= 2 && strcmp(argv[1], "-c") == 0) {
+		if (argc < 3) {
+			fprintf(stderr,
+				"## Error: '-c' option requires the config file to use\n");
+			return -1;
+		}
+		config_file = argv[2];
+		argv += 2;
+		argc -= 2;
+	}
+#endif
+
 	if (argc >= 2 && strcmp(argv[1], "-a") == 0) {
 		if (argc < 3) {
 			fprintf(stderr,
@@ -486,6 +500,19 @@ int fw_setenv(int argc, char *argv[])
 	char *name;
 	char *value = NULL;
 
+#ifdef CONFIG_FILE
+	if (argc >= 2 && strcmp(argv[1], "-c") == 0) {
+		if (argc < 3) {
+			fprintf(stderr,
+				"## Error: '-c' option requires the config file to use\n");
+			return -1;
+		}
+		config_file = argv[2];
+		argv += 2;
+		argc -= 2;
+	}
+#endif
+
 	if (argc < 2) {
 		errno = EINVAL;
 		return -1;
@@ -1364,9 +1391,9 @@ static int parse_config ()
 
 #if defined(CONFIG_FILE)
 	/* Fills in DEVNAME(), ENVSIZE(), DEVESIZE(). Or don't. */
-	if (get_config (CONFIG_FILE)) {
+	if (get_config (config_file)) {
 		fprintf (stderr,
-			"Cannot parse config file: %s\n", strerror (errno));
+			"Cannot parse config file '%s': %s\n", config_file, strerror (errno));
 		return -1;
 	}
 #else

tools/env/fw_env_main.c

@@ -50,8 +50,13 @@ void usage(void)
 
 	fprintf(stderr, "fw_printenv/fw_setenv, "
 		"a command line interface to U-Boot environment\n\n"
+#ifndef CONFIG_FILE
 		"usage:\tfw_printenv [-a key] [-n] [variable name]\n"
 		"\tfw_setenv [-a key] [variable name] [variable value]\n"
+#else
+		"usage:\tfw_printenv [-c /my/fw_env.config] [-a key] [-n] [variable name]\n"
+		"\tfw_setenv [-c /my/fw_env.config] [-a key] [variable name] [variable value]\n"
+#endif
 		"\tfw_setenv -s [ file ]\n"
 		"\tfw_setenv -s - < [ file ]\n\n"
 		"The file passed as argument contains only pairs "
@@ -98,12 +103,15 @@ int main(int argc, char *argv[])
 		cmdname = p + 1;
 	}
 
-	while ((c = getopt_long (argc, argv, "a:ns:h",
+	while ((c = getopt_long (argc, argv, "a:c:ns:h",
 		long_options, NULL)) != EOF) {
 		switch (c) {
 		case 'a':
 			/* AES key, handled later */
 			break;
+		case 'c':
+			/* handled later */
+			break;
 		case 'n':
 			/* handled in fw_printenv */
 			break;