Lines Matching +full:key +full:- +full:value
1 .. SPDX-License-Identifier: GPL-2.0
15 additional key-value data when booting the kernel in an efficient way.
16 This allows administrators to pass a structured-Key config file.
21 The boot config syntax is a simple structured key-value. Each key consists
22 of dot-connected-words, and key and value are connected by ``=``. The value
23 has to be terminated by semi-colon (``;``) or newline (``\n``).
24 For array value, array entries are separated by comma (``,``). ::
26 KEY[.WORD[...]] = VALUE[, VALUE2[...]][;]
30 Each key word must contain only alphabets, numbers, dash (``-``) or underscore
31 (``_``). And each value only contains printable characters or spaces except
32 for delimiters such as semi-colon (``;``), new-line (``\n``), comma (``,``),
35 If you want to use those delimiters in a value, you can use either double-
36 quotes (``"VALUE"``) or single-quotes (``'VALUE'``) to quote it. Note that
39 There can be a key which doesn't have value or has an empty value. Those keys
40 are used for checking if the key exists or not (like a boolean).
42 Key-Value Syntax
43 ----------------
62 In both styles, same key words are automatically merged when parsing it
63 at boot time. So you can append similar trees or key-values.
65 Same-key Values
66 ---------------
68 It is prohibited that two or more values or arrays share a same-key.
72 foo = qux # !ERROR! we can not re-define same key
74 If you want to update the value, you must use the override operator
80 then, the ``qux`` is assigned to ``foo`` key. This is useful for
81 overriding the default value by adding (partial) custom bootconfigs
84 If you want to append the value to existing key as an array member,
90 In this case, the key ``foo`` has ``bar``, ``baz`` and ``qux``.
92 However, a sub-key and a value can not co-exist under a parent key.
96 foo.bar = value2 # !ERROR! subkey "bar" and value "value1" can NOT co-exist
101 --------
103 The config syntax accepts shell-script style comments. The comments starting
109 foo = value # value is set to foo.
116 foo = value
119 Note that you can not put a comment between value and delimiter(``,`` or
122 key = 1 # comment
129 /proc/bootconfig is a user-space interface of the boot config.
130 Unlike /proc/cmdline, this file shows the key-value style list.
131 Each key-value pair is shown in each line with following style::
133 KEY[.WORDS...] = "[VALUE]"[,"VALUE2"...]
141 checksum and 12-byte magic word as below.
145 The size and checksum fields are unsigned 32bit little endian value.
163 # make -C tools/bootconfig
168 # tools/bootconfig/bootconfig -a your-config /boot/initrd.img-X.Y.Z
170 To remove the config from the image, you can use -d option as below::
172 # tools/bootconfig/bootconfig -d /boot/initrd.img-X.Y.Z
180 Currently the maximum config size size is 32KB and the total key-words (not
181 key-value entries) must be under 1024 nodes.
183 more than 2 nodes (a key-word and a value). So theoretically, it will be
184 up to 512 key-value pairs. If keys contains 3 words in average, it can
185 contain 256 key-value pairs. In most cases, the number of config items
197 User can query or loop on key-value pairs, also it is possible to find
198 a root (prefix) key node and find key-values under that node.
200 If you have a key string, you can query the value directly with the key
202 config, you can use xbc_for_each_key_value() to iterate key-value pairs.
204 each array's value, e.g.::
207 xbc_find_value("key.word", &vnode);
209 xbc_array_for_each_value(vnode, value) {
210 printk("%s ", value);
217 But the most typical usage is to get the named value under prefix
220 root = xbc_find_node("key.prefix");
221 value = xbc_node_find_value(root, "option", &vnode);
223 xbc_node_for_each_array_value(root, "array-option", value, anode) {
227 This accesses a value of "key.prefix.option" and an array of
228 "key.prefix.array-option".
231 read-only. All data and keys must be copied if you need to modify it.
237 .. kernel-doc:: include/linux/bootconfig.h
238 .. kernel-doc:: lib/bootconfig.c