env_callback.c
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/*
* (C) Copyright 2012
* Joe Hershberger, National Instruments, joe.hershberger@ni.com
*
* SPDX-License-Identifier: GPL-2.0+
*/
#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
*/
static 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;
}
static int first_call = 1;
static const char *callback_list;
/*
* 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;
char callback_name[256] = "";
struct env_clbk_tbl *clbkp;
int ret = 1;
if (first_call) {
callback_list = getenv(ENV_CALLBACK_VAR);
first_call = 0;
}
/* 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);