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 static int first_call = 1;
  39 static const char *callback_list;
  40
  41 /*
  42  * Look for a possible callback for a newly added variable
  43  * This is called specifically when the variable did not exist in the hash
  44  * previously, so the blanket update did not find this variable.
  45  */
  46 void env_callback_init(ENTRY *var_entry)
  47 {
  48         const char *var_name = var_entry->key;
  49         char callback_name[256] = "";
  50         struct env_clbk_tbl *clbkp;
  51         int ret = 1;
  52
  53         if (first_call) {
  54                 callback_list = getenv(ENV_CALLBACK_VAR);
  55                 first_call = 0;
  56         }
  57
  58         /* look in the ".callbacks" var for a reference to this variable */
  59         if (callback_list != NULL)
  60                 ret = env_attr_lookup(callback_list, var_name, callback_name);
  61
  62         /* only if not found there, look in the static list */
  63         if (ret)
  64                 ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
  65                         callback_name);
  66
  67         /* if an association was found, set the callback pointer */
  68         if (!ret && strlen(callback_name)) {
  69                 clbkp = find_env_callback(callback_name);
  70                 if (clbkp != NULL)
  71 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  72                         var_entry->callback = clbkp->callback + gd->reloc_off;
  73 #else
  74                         var_entry->callback = clbkp->callback;
  75 #endif
  76         }
  77 }
  78
  79 /*
  80  * Called on each existing env var prior to the blanket update since removing
  81  * a callback association should remove its callback.
  82  */
  83 static int clear_callback(ENTRY *entry)
  84 {
  85         entry->callback = NULL;
  86
  87         return 0;
  88 }
  89
  90 /*
  91  * Call for each element in the list that associates variables to callbacks
  92  */
  93 static int set_callback(const char *name, const char *value, void *priv)
  94 {
  95         ENTRY e, *ep;
  96         struct env_clbk_tbl *clbkp;
  97
  98         e.key   = name;
  99         e.data  = NULL;
 100         hsearch_r(e, FIND, &ep, &env_htab, 0);
 101
 102         /* does the env variable actually exist? */
 103         if (ep != NULL) {
 104                 /* the assocaition delares no callback, so remove the pointer */
 105                 if (value == NULL || strlen(value) == 0)
 106                         ep->callback = NULL;
 107                 else {
 108                         /* assign the requested callback */
 109                         clbkp = find_env_callback(value);
 110                         if (clbkp != NULL)
 111 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
 112                                 ep->callback = clbkp->callback + gd->reloc_off;
 113 #else
 114                                 ep->callback = clbkp->callback;
 115 #endif
 116                 }
 117         }
 118
 119         return 0;
 120 }
 121
 122 static int on_callbacks(const char *name, const char *value, enum env_op op,
 123         int flags)
 124 {
 125         /* remove all callbacks */
 126         hwalk_r(&env_htab, clear_callback);
 127
 128         /* configure any static callback bindings */
 129         env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback, NULL);
 130         /* configure any dynamic callback bindings */
 131         env_attr_walk(value, set_callback, NULL);
 132
 133         return 0;
 134 }
 135 U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);