[U-Boot] [RFC PATCH] Allow providing default environment from file

[Rasmus Villemoes]

It is sometimes useful to be able to define the entire default
environment in an external file. This implements a Kconfig option for
allowing that.

It is somewhat annoying to have two visible Kconfig options; it would
probably be more user-friendly to just have the string option (with
empty string obviously meaning not to use this feature). But then we'd
also need a hidden CONFIG that we can use in the #ifdef in
env_default.h, and I don't think one can set a def_bool based on
whether a string-valued config is empty or not.

I've tried to make the accepted format the same as the one the
mkenvimage tool accepts. I have no idea how portable the sed script
implementing the "allow embedded newlines in values" is. Nor do I know
if one can expect xxd to be available.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
---
 Makefile              | 16 ++++++++++++++++
 env/Kconfig           | 18 ++++++++++++++++++
 include/env_default.h |  4 ++++
 3 files changed, 38 insertions(+)

diff --git a/Makefile b/Makefile
index 4981a2ed6f..e5ba5213fd 100644
--- a/Makefile
+++ b/Makefile
@@ -423,6 +423,7 @@ endif
 
 version_h := include/generated/version_autogenerated.h
 timestamp_h := include/generated/timestamp_autogenerated.h
+defaultenv_h := include/generated/defaultenv_autogenerated.h
 
 no-dot-config-targets := clean clobber mrproper distclean \
 			 help %docs check% coccicheck \
@@ -1366,6 +1367,10 @@ ifeq ($(wildcard $(LDSCRIPT)),)
 	@/bin/false
 endif
 
+ifeq ($(CONFIG_DEFAULT_ENV_FROM_FILE),y)
+prepare1: $(defaultenv_h)
+endif
+
 archprepare: prepare1 scripts_basic
 
 prepare0: archprepare FORCE
@@ -1413,12 +1418,23 @@ define filechk_timestamp.h
 	fi)
 endef
 
+define filechk_defaultenv.h
+	(grep -v '^#' | \
+	 grep -v '^$$' | \
+	 tr '\n' '\0' | \
+	 sed -e 's/\\\x0/\n/' | \
+	 xxd -i ; echo ", 0x00" ; )
+endef
+
 $(version_h): include/config/uboot.release FORCE
 	$(call filechk,version.h)
 
 $(timestamp_h): $(srctree)/Makefile FORCE
 	$(call filechk,timestamp.h)
 
+$(defaultenv_h): $(CONFIG_DEFAULT_ENV_FILE:"%"=%) FORCE
+	$(call filechk,defaultenv.h)
+
 # ---------------------------------------------------------------------------
 quiet_cmd_cpp_lds = LDS     $@
 cmd_cpp_lds = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) \
diff --git a/env/Kconfig b/env/Kconfig
index a24370786b..1baebd743b 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -482,4 +482,22 @@ config ENV_SIZE
 
 endif
 
+config DEFAULT_ENV_FROM_FILE
+	bool "Create default environment from file"
+	help
+	  Normally, the default environment is automatically generated
+	  based on the settings of various CONFIG_* options, as well
+	  as the CONFIG_EXTRA_ENV_SETTINGS. By selecting this option,
+	  you can instead define the entire default environment in an
+	  external file.
+
+config DEFAULT_ENV_FILE
+	string "Path to default environment file"
+	depends on DEFAULT_ENV_FROM_FILE
+	help
+	  The path containing the default environment. The format is
+	  the same as accepted by the mkenvimage tool: lines
+	  containing key=value pairs, blank lines and lines beginning
+	  with # are ignored.
+
 endmenu
diff --git a/include/env_default.h b/include/env_default.h
index b574345af2..656d202cc7 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -22,6 +22,7 @@ static char default_environment[] = {
 #else
 const uchar default_environment[] = {
 #endif
+#ifndef CONFIG_DEFAULT_ENV_FROM_FILE
 #ifdef	CONFIG_ENV_CALLBACK_LIST_DEFAULT
 	ENV_CALLBACK_VAR "=" CONFIG_ENV_CALLBACK_LIST_DEFAULT "\0"
 #endif
@@ -108,6 +109,9 @@ const uchar default_environment[] = {
 	CONFIG_EXTRA_ENV_SETTINGS
 #endif
 	"\0"
+#else /* CONFIG_DEFAULT_ENV_FROM_FILE */
+#include "generated/defaultenv_autogenerated.h"
+#endif
 #ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
 	}
 #endif
-- 
2.15.1