xref: /openbmc/u-boot/env/callback.c (revision 407b5b956a2e0facf6668fc8b295f4be9205c83e)
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);
136