env/callback.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * (C) Copyright 2012
   4  * Joe Hershberger, National Instruments, joe.hershberger@ni.com
   5  */
   6
   7 #include <common.h>
   8 #include <environment.h>
   9
  10 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  11 DECLARE_GLOBAL_DATA_PTR;
  12 #endif
  13
  14 /*
  15  * Look up a callback function pointer by name
  16  */
  17 static struct env_clbk_tbl *find_env_callback(const char *name)
  18 {
  19         struct env_clbk_tbl *clbkp;
  20         int i;
  21         int num_callbacks = ll_entry_count(struct env_clbk_tbl, env_clbk);
  22
  23         if (name == NULL)
  24                 return NULL;
  25
  26         /* look up the callback in the linker-list */
  27         for (i = 0, clbkp = ll_entry_start(struct env_clbk_tbl, env_clbk);
  28              i < num_callbacks;
  29              i++, clbkp++) {
  30                 if (strcmp(name, clbkp->name) == 0)
  31                         return clbkp;
  32         }
  33
  34         return NULL;
  35 }
  36
  37 static int first_call = 1;
  38 static const char *callback_list;
  39
  40 /*
  41  * Look for a possible callback for a newly added variable
  42  * This is called specifically when the variable did not exist in the hash
  43  * previously, so the blanket update did not find this variable.
  44  */
  45 void env_callback_init(ENTRY *var_entry)
  46 {
  47         const char *var_name = var_entry->key;
  48         char callback_name[256] = "";
  49         struct env_clbk_tbl *clbkp;
  50         int ret = 1;
  51
  52         if (first_call) {
  53                 callback_list = env_get(ENV_CALLBACK_VAR);
  54                 first_call = 0;
  55         }
  56
  57         /* look in the ".callbacks" var for a reference to this variable */
  58         if (callback_list != NULL)
  59                 ret = env_attr_lookup(callback_list, var_name, callback_name);
  60
  61         /* only if not found there, look in the static list */
  62         if (ret)
  63                 ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
  64                         callback_name);
  65
  66         /* if an association was found, set the callback pointer */
  67         if (!ret && strlen(callback_name)) {
  68                 clbkp = find_env_callback(callback_name);
  69                 if (clbkp != NULL)
  70 #if defined(CONFIG_NEEDS_MANUAL_RELOC)
  71                         var_entry->callback = clbkp->callback + gd->reloc_off;
  72 #else
  73                         var_entry->callback = clbkp->callback;
  74 #endif
  75         }
  76 }
  77
  78 /*
  79  * Called on each existing env var prior to the blanket update since removing
  80  * a callback association should remove its callback.
  81  */
  82 static int clear_callback(ENTRY *entry)
  83 {
  84         entry->callback = NULL;
  85
  86         return 0;
  87 }
  88
  89 /*
  90  * Call for each element in the list that associates variables to callbacks
  91  */
  92 static int set_callback(const char *name, const char *value, void *priv)
  93 {
  94         ENTRY e, *ep;
  95         struct env_clbk_tbl *clbkp;
  96
  97         e.key   = name;
  98         e.data  = NULL;
  99         e.callback = 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);