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 <env.h>
   9 #include <env_internal.h>
  10 #include <asm/global_data.h>
  11
  12 /*
  13  * Look up a callback function pointer by name
  14  */
  15 static struct env_clbk_tbl *find_env_callback(const char *name)
  16 {
  17         struct env_clbk_tbl *clbkp;
  18         int i;
  19         int num_callbacks = ll_entry_count(struct env_clbk_tbl, env_clbk);
  20
  21         if (name == NULL)
  22                 return NULL;
  23
  24         /* look up the callback in the linker-list */
  25         for (i = 0, clbkp = ll_entry_start(struct env_clbk_tbl, env_clbk);
  26              i < num_callbacks;
  27              i++, clbkp++) {
  28                 if (strcmp(name, clbkp->name) == 0)
  29                         return clbkp;
  30         }
  31
  32         return NULL;
  33 }
  34
  35 static int first_call = 1;
  36 static const char *callback_list;
  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(struct env_entry *var_entry)
  44 {
  45         const char *var_name = var_entry->key;
  46         char callback_name[256] = "";
  47         struct env_clbk_tbl *clbkp;
  48         int ret = 1;
  49
  50         if (first_call) {
  51                 callback_list = env_get(ENV_CALLBACK_VAR);
  52                 first_call = 0;
  53         }
  54
  55         var_entry->callback = NULL;
  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                         var_entry->callback = clbkp->callback;
  71         }
  72 }
  73
  74 /*
  75  * Called on each existing env var prior to the blanket update since removing
  76  * a callback association should remove its callback.
  77  */
  78 static int clear_callback(struct env_entry *entry)
  79 {
  80         entry->callback = NULL;
  81
  82         return 0;
  83 }
  84
  85 /*
  86  * Call for each element in the list that associates variables to callbacks
  87  */
  88 static int set_callback(const char *name, const char *value, void *priv)
  89 {
  90         struct env_entry e, *ep;
  91         struct env_clbk_tbl *clbkp;
  92
  93         e.key   = name;
  94         e.data  = NULL;
  95         e.callback = NULL;
  96         hsearch_r(e, ENV_FIND, &ep, &env_htab, 0);
  97
  98         /* does the env variable actually exist? */
  99         if (ep != NULL) {
 100                 /* the assocaition delares no callback, so remove the pointer */
 101                 if (value == NULL || strlen(value) == 0)
 102                         ep->callback = NULL;
 103                 else {
 104                         /* assign the requested callback */
 105                         clbkp = find_env_callback(value);
 106                         if (clbkp != NULL)
 107                                 ep->callback = clbkp->callback;
 108                 }
 109         }
 110
 111         return 0;
 112 }
 113
 114 static int on_callbacks(const char *name, const char *value, enum env_op op,
 115         int flags)
 116 {
 117         /* remove all callbacks */
 118         hwalk_r(&env_htab, clear_callback);
 119
 120         /* configure any static callback bindings */
 121         env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback, NULL);
 122         /* configure any dynamic callback bindings */
 123         env_attr_walk(value, set_callback, NULL);
 124
 125         return 0;
 126 }
 127 U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);