README: U_BOOT_ENV_CALLBACK functions
Describe the interface of environment variable callback functions.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/README b/README
index aee0f73..a91af2a 100644
--- a/README
+++ b/README
@@ -3943,6 +3943,17 @@
regular expression. This allows multiple variables to be connected to
the same callback without explicitly listing them all out.
+The signature of the callback functions is:
+
+ int callback(const char *name, const char *value, enum env_op op, int flags)
+
+* name - changed environment variable
+* value - new value of the environment variable
+* op - operation (create, overwrite, or delete)
+* flags - attributes of the environment variable change, see flags H_* in
+ include/search.h
+
+The return value is 0 if the variable change is accepted and 1 otherwise.
Command Line Parsing:
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