[PATCH v2 2/3] env: add envvar_for_each helper for variable iteration

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Instead of opencoding the iteration where needed, implement a helper
invokes a callback on every variable.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
v1 -> v2:
  - new patch
---
 common/env.c          | 37 +++++++++++++++++++++++++++++++++++++
 include/environment.h |  7 +++++++
 2 files changed, 44 insertions(+)

diff --git a/common/env.c b/common/env.c
index e34e3ac078d6..fd01178aee54 100644
--- a/common/env.c
+++ b/common/env.c
@@ -123,6 +123,21 @@ static const char *getenv_raw(struct list_head *l, const char *name)
 	return NULL;
 }
 
+static int getenv_raw_call(int (*fn)(struct variable_d *v, void *data),
+			   struct list_head *l, void *data)
+{
+	struct variable_d *v;
+	int ret;
+
+	list_for_each_entry(v, l, list) {
+		ret = fn(v, data);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static const char *dev_getenv(const char *name)
 {
 	const char *pos, *val, *dot, *varname;
@@ -179,6 +194,28 @@ const char *getenv(const char *name)
 }
 EXPORT_SYMBOL(getenv);
 
+int envvar_for_each(int (*fn)(struct variable_d *v, void *data), void *data)
+{
+	struct env_context *c;
+	int ret;
+
+	c = context;
+
+	ret = getenv_raw_call(fn, &c->local, data);
+	if (ret)
+		return ret;
+
+	while (c) {
+		ret = getenv_raw_call(fn, &c->global, data);
+		if (ret)
+			return ret;
+		c = c->parent;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(envvar_for_each);
+
 static int setenv_raw(struct list_head *l, const char *name, const char *value)
 {
 	struct variable_d *v;
diff --git a/include/environment.h b/include/environment.h
index f26c68ba3e34..c24796427675 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -31,6 +31,7 @@ const char *var_name(struct variable_d *);
 
 #if IS_ENABLED(CONFIG_ENVIRONMENT_VARIABLES) && IN_PROPER
 const char *getenv(const char *);
+int envvar_for_each(int (*fn)(struct variable_d *v, void *data), void *data);
 int setenv(const char *, const char *);
 int pr_setenv(const char *, const char *fmt, ...)  __attribute__ ((format(__printf__, 2, 3)));
 void export_env_ull(const char *name, unsigned long long val);
@@ -46,6 +47,12 @@ static inline char *getenv(const char *var)
 	return NULL;
 }
 
+static inline int envvar_for_each(int (*fn)(struct list_head *l, void *data),
+				  void *data)
+{
+	return 0;
+}
+
 static inline int setenv(const char *var, const char *val)
 {
 	return 0;
-- 
2.39.5