env: Add support for callbacks to environment vars

Add support for per-variable callbacks to the "hashtable" functions.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

!!!fix comment in callback

5 files changed, 129 insertions, 0 deletions

diff --git a/include/env_attr.h b/include/env_attr.h
new file mode 100644
index 0000000..6ef114f
--- /dev/null
+++ b/include/env_attr.h
@@ -0,0 +1,55 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger@ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ENV_ATTR_H__
+#define __ENV_ATTR_H__
+
+#define ENV_ATTR_LIST_DELIM	','
+#define ENV_ATTR_SEP		':'
+
+/*
+ * env_attr_walk takes as input an "attr_list" that takes the form:
+ *	attributes = [^,:\s]*
+ *	entry = name[:attributes]
+ *	list = entry[,list]
+ * It will call the "callback" function with the "name" and attribute as "value"
+ * The callback may return a non-0 to abort the list walk.
+ * This return value will be passed through to the caller.
+ * 0 is returned on success.
+ */
+extern int env_attr_walk(const char *attr_list,
+	int (*callback)(const char *name, const char *value));
+
+/*
+ * env_attr_lookup takes as input an "attr_list" with the same form as above.
+ * It also takes as input a "name" to look for.
+ * If the name is found in the list, it's value is copied into "attributes".
+ * There is no protection on attributes being too small for the value.
+ * It returns -1 if attributes is NULL, 1 if "name" is not found, 2 if
+ * "attr_list" is NULL.
+ * Returns 0 on success.
+ */
+extern int env_attr_lookup(const char *attr_list, const char *name,
+	char *attributes);
+
+#endif /* __ENV_ATTR_H__ */
diff --git a/include/env_callback.h b/include/env_callback.h
new file mode 100644
index 0000000..5a460f3
--- /dev/null
+++ b/include/env_callback.h
@@ -0,0 +1,62 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger@ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ENV_CALLBACK_H__
+#define __ENV_CALLBACK_H__
+
+#include <linker_lists.h>
+#include <search.h>
+
+#define ENV_CALLBACK_VAR ".callbacks"
+
+/* Board configs can define additional static callback bindings */
+#ifndef CONFIG_ENV_CALLBACK_LIST_STATIC
+#define CONFIG_ENV_CALLBACK_LIST_STATIC
+#endif
+
+/*
+ * This list of callback bindings is static, but may be overridden by defining
+ * a new association in the ".callbacks" environment variable.
+ */
+#define ENV_CALLBACK_LIST_STATIC ENV_CALLBACK_VAR ":callbacks," \
+	CONFIG_ENV_CALLBACK_LIST_STATIC
+
+struct env_clbk_tbl {
+	const char *name;		/* Callback name */
+	int (*callback)(const char *name, const char *value, enum env_op op,
+		int flags);
+};
+
+struct env_clbk_tbl *find_env_callback(const char *);
+void env_callback_init(ENTRY *var_entry);
+
+/*
+ * Define a callback that can be associated with variables.
+ * when associated through the ".callbacks" environment variable, the callback
+ * will be executed any time the variable is inserted, overwritten, or deleted.
+ */
+#define U_BOOT_ENV_CALLBACK(name, callback) \
+	ll_entry_declare(struct env_clbk_tbl, name, env_clbk, env_clbk) = \
+	{#name, callback}
+
+#endif /* __ENV_CALLBACK_H__ */
diff --git a/include/env_default.h b/include/env_default.h
index a1db73a..d05eba1 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -24,6 +24,8 @@
  * MA 02111-1307 USA
  */
 
+#include <env_callback.h>
+
 #ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
 env_t environment __PPCENV__ = {
 	ENV_CRC,	/* CRC Sum */
@@ -36,6 +38,9 @@ static char default_environment[] = {
 #else
 const uchar default_environment[] = {
 #endif
+#ifdef	CONFIG_ENV_CALLBACK_LIST_DEFAULT
+	ENV_CALLBACK_VAR "=" CONFIG_ENV_CALLBACK_LIST_DEFAULT "\0"
+#endif
 #ifdef	CONFIG_BOOTARGS
 	"bootargs="	CONFIG_BOOTARGS			"\0"
 #endif
diff --git a/include/environment.h b/include/environment.h
index 4b19f32..6c30215 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -164,6 +164,8 @@ extern void env_reloc(void);
 
 #ifndef DO_DEPS_ONLY
 
+#include <env_attr.h>
+#include <env_callback.h>
 #include <search.h>
 
 extern struct hsearch_data env_htab;
diff --git a/include/search.h b/include/search.h
index 1e48deb..d68e24a 100644
--- a/include/search.h
+++ b/include/search.h
@@ -47,6 +47,8 @@ typedef enum {
 typedef struct entry {
 	const char *key;
 	char *data;
+	int (*callback)(const char *name, const char *value, enum env_op op,
+		int flags);
 } ENTRY;
 
 /* Opaque type for internal use.  */
@@ -120,6 +122,9 @@ extern int himport_r(struct hsearch_data *__htab,
 		     const char *__env, size_t __size, const char __sep,
 		     int __flag, int nvars, char * const vars[]);
 
+/* Walk the whole table calling the callback on each element */
+extern int hwalk_r(struct hsearch_data *__htab, int (*callback)(ENTRY *));
+
 /* Flags for himport_r(), hexport_r(), hdelete_r(), and hsearch_r() */
 #define H_NOCLEAR	(1 << 0) /* do not clear hash table before importing */
 #define H_FORCE		(1 << 1) /* overwrite read-only/write-once variables */