common/env_callback.c

   1 /*
   2  * (C) Copyright 2012
   3  * Joe Hershberger, National Instruments, joe.hershberger@ni.com
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <common.h>
  25 #include <environment.h>
  26
  27 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  28 DECLARE_GLOBAL_DATA_PTR;
  29 #endif
  30
  31 /*
  32  * Look up a callback function pointer by name
  33  */
  34 static struct env_clbk_tbl *find_env_callback(const char *name)
  35 {
  36         struct env_clbk_tbl *clbkp;
  37         int i;
  38         int num_callbacks = ll_entry_count(struct env_clbk_tbl, env_clbk);
  39
  40         if (name == NULL)
  41                 return NULL;
  42
  43         /* look up the callback in the linker-list */
  44         for (i = 0, clbkp = ll_entry_start(struct env_clbk_tbl, env_clbk);
  45              i < num_callbacks;
  46              i++, clbkp++) {
  47                 if (strcmp(name, clbkp->name) == 0)
  48                         return clbkp;
  49         }
  50
  51         return NULL;
  52 }
  53
  54 /*
  55  * Look for a possible callback for a newly added variable
  56  * This is called specifically when the variable did not exist in the hash
  57  * previously, so the blanket update did not find this variable.
  58  */
  59 void env_callback_init(ENTRY *var_entry)
  60 {
  61         const char *var_name = var_entry->key;
  62         const char *callback_list = getenv(ENV_CALLBACK_VAR);
  63         char callback_name[256] = "";
  64         struct env_clbk_tbl *clbkp;
  65         int ret = 1;
  66
  67         /* look in the ".callbacks" var for a reference to this variable */
  68         if (callback_list != NULL)
  69                 ret = env_attr_lookup(callback_list, var_name, callback_name);
  70
  71         /* only if not found there, look in the static list */
  72         if (ret)
  73                 ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
  74                         callback_name);
  75
  76         /* if an association was found, set the callback pointer */
  77         if (!ret && strlen(callback_name)) {
  78                 clbkp = find_env_callback(callback_name);
  79                 if (clbkp != NULL)
  80 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  81                         var_entry->callback = clbkp->callback + gd->reloc_off;
  82 #else
  83                         var_entry->callback = clbkp->callback;
  84 #endif
  85         }
  86 }
  87
  88 /*
  89  * Called on each existing env var prior to the blanket update since removing
  90  * a callback association should remove its callback.
  91  */
  92 static int clear_callback(ENTRY *entry)
  93 {
  94         entry->callback = NULL;
  95
  96         return 0;
  97 }
  98
  99 /*
 100  * Call for each element in the list that associates variables to callbacks
 101  */
 102 static int set_callback(const char *name, const char *value)
 103 {
 104         ENTRY e, *ep;
 105         struct env_clbk_tbl *clbkp;
 106
 107         e.key   = name;
 108         e.data  = NULL;
 109         hsearch_r(e, FIND, &ep, &env_htab, 0);
 110
 111         /* does the env variable actually exist? */
 112         if (ep != NULL) {
 113                 /* the assocaition delares no callback, so remove the pointer */
 114                 if (value == NULL || strlen(value) == 0)
 115                         ep->callback = NULL;
 116                 else {
 117                         /* assign the requested callback */
 118                         clbkp = find_env_callback(value);
 119                         if (clbkp != NULL)
 120 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
 121                                 ep->callback = clbkp->callback + gd->reloc_off;
 122 #else
 123                                 ep->callback = clbkp->callback;
 124 #endif
 125                 }
 126         }
 127
 128         return 0;
 129 }
 130
 131 static int on_callbacks(const char *name, const char *value, enum env_op op,
 132         int flags)
 133 {
 134         /* remove all callbacks */
 135         hwalk_r(&env_htab, clear_callback);
 136
 137         /* configure any static callback bindings */
 138         env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback);
 139         /* configure any dynamic callback bindings */
 140         env_attr_walk(value, set_callback);
 141
 142         return 0;
 143 }
 144 U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);