[PATCH 01/12] env: Complete generic support for writable list

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka at siemens.com>

This completes what 890feecaab72 started by selecting ENV_APPEND and
ENV_IS_NOWHERE and by moving this driver to top if the list. This
ensures that load operations pick up both the default env and the
permitted parts of the next-prio location. When writing though, we must
not use NOWHERE and rather need to forward directly to the first
external location.

With this change, boards only need to define the list of writable
variables but no longer have to provide a custom env_get_location
implementation.

CC: Joe Hershberger <joe.hershberger at ni.com>
CC: Marek Vasut <marex at denx.de>
Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
---
 env/Kconfig |  2 ++
 env/env.c   | 17 ++++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/env/Kconfig b/env/Kconfig
index 2f625b22575..00db63a136c 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -696,6 +696,8 @@ config ENV_APPEND
 
 config ENV_WRITEABLE_LIST
 	bool "Permit write access only to listed variables"
+	select ENV_IS_NOWHERE
+	select ENV_APPEND
 	help
 	  If defined, only environment variables which explicitly set the 'w'
 	  writeable flag can be written and modified at runtime. No variables
diff --git a/env/env.c b/env/env.c
index 69848fb0608..3b24f7941c0 100644
--- a/env/env.c
+++ b/env/env.c
@@ -54,6 +54,13 @@ static struct env_driver *_env_driver_lookup(enum env_location loc)
 }
 
 static enum env_location env_locations[] = {
+#if defined(CONFIG_ENV_IS_NOWHERE) && defined(CONFIG_ENV_WRITEABLE_LIST)
+	/*
+	 * In writeable-list mode, the built-in env must have highest prio
+	 * while loading. This is achieved by moving ENVL_NOWHERE to the front.
+	 */
+	ENVL_NOWHERE,
+#endif
 #ifdef CONFIG_ENV_IS_IN_EEPROM
 	ENVL_EEPROM,
 #endif
@@ -87,7 +94,7 @@ static enum env_location env_locations[] = {
 #ifdef CONFIG_ENV_IS_IN_UBI
 	ENVL_UBI,
 #endif
-#ifdef CONFIG_ENV_IS_NOWHERE
+#if defined(CONFIG_ENV_IS_NOWHERE) && !defined(CONFIG_ENV_WRITEABLE_LIST)
 	ENVL_NOWHERE,
 #endif
 };
@@ -133,6 +140,14 @@ __weak enum env_location arch_env_get_location(enum env_operation op, int prio)
 	if (prio >= ARRAY_SIZE(env_locations))
 		return ENVL_UNKNOWN;
 
+#ifdef CONFIG_ENV_WRITEABLE_LIST
+	/*
+	 * In writeable-list mode, ENVL_NOWHERE gains highest prio. This blocks
+	 * writing, though. So return the location of the next prio instead.
+	 */
+	if ((op == ENVOP_SAVE || op == ENVOP_ERASE) && prio == 0)
+		prio++;
+#endif
 	return env_locations[prio];
 }
 
-- 
2.35.3