common/env_callback.c

   1 /*
   2  * (C) Copyright 2012
   3  * Joe Hershberger, National Instruments, joe.hershberger@ni.com
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 #include <common.h>
   9 #include <environment.h>
  10
  11 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  12 DECLARE_GLOBAL_DATA_PTR;
  13 #endif
  14
  15 /*
  16  * Look up a callback function pointer by name
  17  */
  18 static struct env_clbk_tbl *find_env_callback(const char *name)
  19 {
  20         struct env_clbk_tbl *clbkp;
  21         int i;
  22         int num_callbacks = ll_entry_count(struct env_clbk_tbl, env_clbk);
  23
  24         if (name == NULL)
  25                 return NULL;
  26
  27         /* look up the callback in the linker-list */
  28         for (i = 0, clbkp = ll_entry_start(struct env_clbk_tbl, env_clbk);
  29              i < num_callbacks;
  30              i++, clbkp++) {
  31                 if (strcmp(name, clbkp->name) == 0)
  32                         return clbkp;
  33         }
  34
  35         return NULL;
  36 }
  37
  38 /*
  39  * Look for a possible callback for a newly added variable
  40  * This is called specifically when the variable did not exist in the hash
  41  * previously, so the blanket update did not find this variable.
  42  */
  43 void env_callback_init(ENTRY *var_entry)
  44 {
  45         const char *var_name = var_entry->key;
  46         const char *callback_list = getenv(ENV_CALLBACK_VAR);
  47         char callback_name[256] = "";
  48         struct env_clbk_tbl *clbkp;
  49         int ret = 1;
  50
  51         /* look in the ".callbacks" var for a reference to this variable */
  52         if (callback_list != NULL)
  53                 ret = env_attr_lookup(callback_list, var_name, callback_name);
  54
  55         /* only if not found there, look in the static list */
  56         if (ret)
  57                 ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
  58                         callback_name);
  59
  60         /* if an association was found, set the callback pointer */
  61         if (!ret && strlen(callback_name)) {
  62                 clbkp = find_env_callback(callback_name);
  63                 if (clbkp != NULL)
  64 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  65                         var_entry->callback = clbkp->callback + gd->reloc_off;
  66 #else
  67                         var_entry->callback = clbkp->callback;
  68 #endif
  69         }
  70 }
  71
  72 /*
  73  * Called on each existing env var prior to the blanket update since removing
  74  * a callback association should remove its callback.
  75  */
  76 static int clear_callback(ENTRY *entry)
  77 {
  78         entry->callback = NULL;
  79
  80         return 0;
  81 }
  82
  83 /*
  84  * Call for each element in the list that associates variables to callbacks
  85  */
  86 static int set_callback(const char *name, const char *value)
  87 {
  88         ENTRY e, *ep;
  89         struct env_clbk_tbl *clbkp;
  90
  91         e.key   = name;
  92         e.data  = NULL;
  93         hsearch_r(e, FIND, &ep, &env_htab, 0);
  94
  95         /* does the env variable actually exist? */
  96         if (ep != NULL) {
  97                 /* the assocaition delares no callback, so remove the pointer */
  98                 if (value == NULL || strlen(value) == 0)
  99                         ep->callback = NULL;
 100                 else {
 101                         /* assign the requested callback */
 102                         clbkp = find_env_callback(value);
 103                         if (clbkp != NULL)
 104 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
 105                                 ep->callback = clbkp->callback + gd->reloc_off;
 106 #else
 107                                 ep->callback = clbkp->callback;
 108 #endif
 109                 }
 110         }
 111
 112         return 0;
 113 }
 114
 115 static int on_callbacks(const char *name, const char *value, enum env_op op,
 116         int flags)
 117 {
 118         /* remove all callbacks */
 119         hwalk_r(&env_htab, clear_callback);
 120
 121         /* configure any static callback bindings */
 122         env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback);
 123         /* configure any dynamic callback bindings */
 124         env_attr_walk(value, set_callback);
 125
 126         return 0;
 127 }
 128 U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);