[PATCH V2 01/13] 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
use the regular ordering.

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   | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/env/Kconfig b/env/Kconfig
index 24111dfaf47..05b5fbf17d1 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -715,6 +715,8 @@ 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..d0649f9540d 100644
--- a/env/env.c
+++ b/env/env.c
@@ -133,6 +133,28 @@ __weak enum env_location arch_env_get_location(enum env_operation op, int prio)
 	if (prio >= ARRAY_SIZE(env_locations))
 		return ENVL_UNKNOWN;
 
+	if (IS_ENABLED(CONFIG_ENV_WRITEABLE_LIST)) {
+		/*
+		 * In writeable-list mode, ENVL_NOWHERE gains highest prio by
+		 * virtually injecting it at prio 0.
+		 */
+		if (prio == 0) {
+			/*
+			 * Avoid the injection for write operations as that
+			 * would block it.
+			 */
+			if (op != ENVOP_SAVE && op != ENVOP_ERASE)
+				return ENVL_NOWHERE;
+		} else {
+			/*
+			 * always subtract 1, also for writing because
+			 * env_load_prio, which is used for writing, was
+			 * initialized with that offset.
+			 */
+			prio--;
+		}
+	}
+
 	return env_locations[prio];
 }
 
-- 
2.35.3