env: register erase command

this patch adds basic changes for adding a erase-subcommand to env

with this command the environment stored on non-volatile storage written
by saveenv can be cleared.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>

squashed fixes
 - start message with "Erasing"
 - mark erase-function as optional
 - env: separate eraseenv from saveenv

Suggested-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>

cmd/Kconfig

@@ -408,6 +408,14 @@ config CMD_SAVEENV
 	  Save all environment variables into the compiled-in persistent
 	  storage.
 
+config CMD_ERASEENV
+	bool "eraseenv"
+	default n
+	depends on CMD_SAVEENV
+	help
+	  Erase environment variables from the compiled-in persistent
+	  storage.
+
 config CMD_ENV_EXISTS
 	bool "env exists"
 	default y

cmd/nvedit.c

@@ -767,6 +767,20 @@ U_BOOT_CMD(
 	"save environment variables to persistent storage",
 	""
 );
+
+#if defined(CONFIG_CMD_ERASEENV)
+static int do_env_erase(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	return env_erase() ? 1 : 0;
+}
+
+U_BOOT_CMD(
+	eraseenv, 1, 0,	do_env_erase,
+	"erase environment variables from persistent storage",
+	""
+);
+#endif
 #endif
 #endif /* CONFIG_SPL_BUILD */
 
@@ -1316,6 +1330,9 @@ static cmd_tbl_t cmd_env_sub[] = {
 #endif
 #if defined(CONFIG_CMD_SAVEENV) && defined(ENV_IS_IN_DEVICE)
 	U_BOOT_CMD_MKENT(save, 1, 0, do_env_save, "", ""),
+#if defined(CONFIG_CMD_ERASEENV)
+	U_BOOT_CMD_MKENT(erase, 1, 0, do_env_erase, "", ""),
+#endif
 #endif
 	U_BOOT_CMD_MKENT(set, CONFIG_SYS_MAXARGS, 0, do_env_set, "", ""),
 #if defined(CONFIG_CMD_ENV_EXISTS)
@@ -1396,6 +1413,9 @@ static char env_help_text[] =
 #endif
 #if defined(CONFIG_CMD_SAVEENV) && defined(ENV_IS_IN_DEVICE)
 	"env save - save environment\n"
+#if defined(CONFIG_CMD_ERASEENV)
+	"env erase - erase environment\n"
+#endif
 #endif
 #if defined(CONFIG_CMD_NVEDIT_EFI)
 	"env set -e name [arg ...] - set UEFI variable; unset if 'arg' not specified\n"

env/env.c

@@ -24,6 +24,8 @@ void env_fix_drivers(void)
 			entry->load += gd->reloc_off;
 		if (entry->save)
 			entry->save += gd->reloc_off;
+		if (entry->erase)
+			entry->erase += gd->reloc_off;
 		if (entry->init)
 			entry->init += gd->reloc_off;
 	}
@@ -254,6 +256,34 @@ int env_save(void)
 	return -ENODEV;
 }
 
+int env_erase(void)
+{
+	struct env_driver *drv;
+
+	drv = env_driver_lookup(ENVOP_ERASE, gd->env_load_prio);
+	if (drv) {
+		int ret;
+
+		if (!drv->erase)
+			return -ENODEV;
+
+		if (!env_has_inited(drv->location))
+			return -ENODEV;
+
+		printf("Erasing Environment on %s... ", drv->name);
+		ret = drv->erase();
+		if (ret)
+			printf("Failed (%d)\n", ret);
+		else
+			printf("OK\n");
+
+		if (!ret)
+			return 0;
+	}
+
+	return -ENODEV;
+}
+
 int env_init(void)
 {
 	struct env_driver *drv;

include/environment.h

@@ -200,6 +200,7 @@ enum env_operation {
 	ENVOP_INIT,	/* we want to call the init function */
 	ENVOP_LOAD,	/* we want to call the load function */
 	ENVOP_SAVE,	/* we want to call the save function */
+	ENVOP_ERASE,	/* we want to call the erase function */
 };
 
 struct env_driver {
@@ -225,6 +226,15 @@ struct env_driver {
 	 */
 	int (*save)(void);
 
+	/**
+	 * erase() - Erase the environment on storage
+	 *
+	 * This method is optional and required for 'eraseenv' to work.
+	 *
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*erase)(void);
+
 	/**
 	 * init() - Set up the initial pre-relocation environment
 	 *
@@ -303,6 +313,13 @@ int env_load(void);
  */
 int env_save(void);
 
+/**
+ * env_erase() - Erase the environment on storage
+ *
+ * @return 0 if OK, -ve on error
+ */
+int env_erase(void);
+
 /**
  * env_fix_drivers() - Updates envdriver as per relocation
  */