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authorJoe Hershberger <joe.hershberger@ni.com>2012-12-11 22:16:24 -0600
committerTom Rini <trini@ti.com>2012-12-13 11:46:55 -0700
commit170ab11075d3be56e89d6444abf1148329130f4b (patch)
treed3088ad532f4f4a0082f625ce50cfd120d6a6a1d /common/env_callback.c
parentbe11235ab802844e12d84921a38fd8ae4ddda080 (diff)
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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
Diffstat (limited to 'common/env_callback.c')
-rw-r--r--common/env_callback.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/common/env_callback.c b/common/env_callback.c
new file mode 100644
index 0000000..78ca367
--- /dev/null
+++ b/common/env_callback.c
@@ -0,0 +1,144 @@
+/*
+ * (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
+ */
+
+#include <common.h>
+#include <environment.h>
+
+#if defined(CONFIG_NEEDS_MANUAL_RELOC)
+DECLARE_GLOBAL_DATA_PTR;
+#endif
+
+/*
+ * Look up a callback function pointer by name
+ */
+struct env_clbk_tbl *find_env_callback(const char *name)
+{
+ struct env_clbk_tbl *clbkp;
+ int i;
+ int num_callbacks = ll_entry_count(struct env_clbk_tbl, env_clbk);
+
+ if (name == NULL)
+ return NULL;
+
+ /* look up the callback in the linker-list */
+ for (i = 0, clbkp = ll_entry_start(struct env_clbk_tbl, env_clbk);
+ i < num_callbacks;
+ i++, clbkp++) {
+ if (strcmp(name, clbkp->name) == 0)
+ return clbkp;
+ }
+
+ return NULL;
+}
+
+/*
+ * Look for a possible callback for a newly added variable
+ * This is called specifically when the variable did not exist in the hash
+ * previously, so the blanket update did not find this variable.
+ */
+void env_callback_init(ENTRY *var_entry)
+{
+ const char *var_name = var_entry->key;
+ const char *callback_list = getenv(ENV_CALLBACK_VAR);
+ char callback_name[256] = "";
+ struct env_clbk_tbl *clbkp;
+ int ret = 1;
+
+ /* look in the ".callbacks" var for a reference to this variable */
+ if (callback_list != NULL)
+ ret = env_attr_lookup(callback_list, var_name, callback_name);
+
+ /* only if not found there, look in the static list */
+ if (ret)
+ ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
+ callback_name);
+
+ /* if an association was found, set the callback pointer */
+ if (!ret && strlen(callback_name)) {
+ clbkp = find_env_callback(callback_name);
+ if (clbkp != NULL)
+#if defined(CONFIG_NEEDS_MANUAL_RELOC)
+ var_entry->callback = clbkp->callback + gd->reloc_off;
+#else
+ var_entry->callback = clbkp->callback;
+#endif
+ }
+}
+
+/*
+ * Called on each existing env var prior to the blanket update since removing
+ * a callback association should remove its callback.
+ */
+static int clear_callback(ENTRY *entry)
+{
+ entry->callback = NULL;
+
+ return 0;
+}
+
+/*
+ * Call for each element in the list that associates variables to callbacks
+ */
+static int set_callback(const char *name, const char *value)
+{
+ ENTRY e, *ep;
+ struct env_clbk_tbl *clbkp;
+
+ e.key = name;
+ e.data = NULL;
+ hsearch_r(e, FIND, &ep, &env_htab, 0);
+
+ /* does the env variable actually exist? */
+ if (ep != NULL) {
+ /* the assocaition delares no callback, so remove the pointer */
+ if (value == NULL || strlen(value) == 0)
+ ep->callback = NULL;
+ else {
+ /* assign the requested callback */
+ clbkp = find_env_callback(value);
+ if (clbkp != NULL)
+#if defined(CONFIG_NEEDS_MANUAL_RELOC)
+ ep->callback = clbkp->callback + gd->reloc_off;
+#else
+ ep->callback = clbkp->callback;
+#endif
+ }
+ }
+
+ return 0;
+}
+
+static int on_callbacks(const char *name, const char *value, enum env_op op,
+ int flags)
+{
+ /* remove all callbacks */
+ hwalk_r(&env_htab, clear_callback);
+
+ /* configure any static callback bindings */
+ env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback);
+ /* configure any dynamic callback bindings */
+ env_attr_walk(value, set_callback);
+
+ return 0;
+}
+U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);