[U-Boot] [PATCH 06/17] env: Add the ability to merge the saved env with the default.

[Simon Glass]

From: Doug Anderson <dianders at chromium.org>

This is a useful mechanism any time you have a way to update the
saved environment outside of u-boot.  This can be a tool like
fw_setenv.

Signed-off-by: Doug Anderson <dianders at chromium.org>
Signed-off-by: Simon Glass <sjg at chromium.org>
---
 README              |    7 +++++++
 common/env_common.c |   25 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/README b/README
index 05c5688..785953f 100644
--- a/README
+++ b/README
@@ -4098,6 +4098,13 @@ Please note that changes to some configuration parameters may take
 only effect after the next boot (yes, that's just like Windoze :-).
 
 
+If merge_with_default is in the loaded environment, and is not "0", then
+the loaded environment will be merged on top of the default environment
+instead of just replacing it. This means that your saved environment can
+contain only the variables you need to change from the default. This is
+useful with fw_setenv.
+
+
 Command Line Parsing:
 =====================
 
diff --git a/common/env_common.c b/common/env_common.c
index 3d3cb70..f7fe7a2 100644
--- a/common/env_common.c
+++ b/common/env_common.c
@@ -34,6 +34,19 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+/*
+ * Create a saved enviroment with this env variable set to "1" to merge the
+ * saved environment on top of the default environment.  The idea is that your
+ * saved environment would just contain variables that you'd like to override
+ * from the default so that as you update u-boot (w/ potential changes to the
+ * default) you get all the updates.
+ *
+ * This is really most useful when you have a tool like fw_setenv to manage
+ * your saved environment.  Using 'saveenv' to save your environment will saved
+ * the _merged_ environment (AKA it won't unmerge things).
+ */
+#define MERGE_WITH_DEFAULT "merge_with_default"
+
 /************************************************************************
  * Default settings to be used when no valid environment is found
  */
@@ -156,7 +169,19 @@ int env_import(const char *buf, int check)
 
 	if (himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0', 0,
 			0, NULL, 0 /* do_apply */)) {
+		char *merge_val;
+
 		gd->flags |= GD_FLG_ENV_READY;
+		merge_val = getenv(MERGE_WITH_DEFAULT);
+
+		if (merge_val != NULL && merge_val[0] != '0') {
+			set_default_env("");
+			himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0',
+				  H_NOCLEAR, 0, NULL, 0 /* do_apply */);
+			hdelete_r(MERGE_WITH_DEFAULT, &env_htab,
+				  0 /* do_apply */);
+			puts("Merged saved with default environment\n\n");
+		}
 		return 1;
 	}
 
-- 
1.7.7.3