source: MondoRescue/branches/stable/mindi-busybox/scripts/config/Kconfig-language.txt @ 821

Last change on this file since 821 was 821, checked in by Bruno Cornec, 13 years ago

Addition of busybox 1.2.1 as a mindi-busybox new package
This should avoid delivering binary files in mindi not built there (Fedora and Debian are quite serious about that)

File size: 8.3 KB
Line 
1Introduction
2------------
3
4The configuration database is collection of configuration options
5organized in a tree structure:
6
7    +- Code maturity level options
8    |  +- Prompt for development and/or incomplete code/drivers
9    +- General setup
10    |  +- Networking support
11    |  +- System V IPC
12    |  +- BSD Process Accounting
13    |  +- Sysctl support
14    +- Loadable module support
15    |  +- Enable loadable module support
16    |     +- Set version information on all module symbols
17    |     +- Kernel module loader
18    +- ...
19
20Every entry has its own dependencies. These dependencies are used
21to determine the visible of an entry. Any child entry is only
22visible if its parent entry is also visible.
23
24Menu entries
25------------
26
27Most entries define a config option, all other entries help to organize
28them. A single configuration option is defined like this:
29
30config MODVERSIONS
31    bool "Set version information on all module symbols"
32    depends MODULES
33    help
34      Usually, modules have to be recompiled whenever you switch to a new
35      kernel.  ...
36
37Every line starts with a key word and can be followed by multiple
38arguments.  "config" starts a new config entry. The following lines
39define attributes for this config option. Attributes can be the type of
40the config option, input prompt, dependencies, help text and default
41values. A config option can be defined multiple times with the same
42name, but every definition can have only a single input prompt and the
43type must not conflict.
44
45Menu attributes
46---------------
47
48A menu entry can have a number of attributes. Not all of them are
49applicable everywhere (see syntax).
50
51- type definition: "bool"/"tristate"/"string"/"hex"/"integer"
52  Every config option must have a type. There are only two basic types:
53  tristate and string, the other types base on these two. The type
54  definition optionally accepts an input prompt, so these two examples
55  are equivalent:
56
57    bool "Networking support"
58  and
59    bool
60    prompt "Networking support"
61
62- input prompt: "prompt" <prompt> ["if" <expr>]
63  Every menu entry can have at most one prompt, which is used to display
64  to the user. Optionally dependencies only for this prompt can be added
65  with "if".
66
67- default value: "default" <symbol> ["if" <expr>]
68  A config option can have any number of default values. If multiple
69  default values are visible, only the first defined one is active.
70  Default values are not limited to the menu entry, where they are
71  defined, this means the default can be defined somewhere else or be
72  overridden by an earlier definition.
73  The default value is only assigned to the config symbol if no other
74  value was set by the user (via the input prompt above). If an input
75  prompt is visible the default value is presented to the user and can
76  be overridden by him.
77  Optionally dependencies only for this default value can be added with
78  "if".
79
80- dependencies: "depends on"/"requires" <expr>
81  This defines a dependency for this menu entry. If multiple
82  dependencies are defined they are connected with '&&'. Dependencies
83  are applied to all other options within this menu entry (which also
84  accept "if" expression), so these two examples are equivalent:
85
86    bool "foo" if BAR
87    default y if BAR
88  and
89    depends on BAR
90    bool "foo"
91    default y
92
93- help text: "help"
94  This defines a help text. The end of the help text is determined by
95  the level indentation, this means it ends at the first line which has
96  a smaller indentation than the first line of the help text.
97
98
99Menu dependencies
100-----------------
101
102Dependencies define the visibility of a menu entry and can also reduce
103the input range of tristate symbols. The tristate logic used in the
104expressions uses one more state than normal boolean logic to express the
105module state. Dependency expressions have the following syntax:
106
107<expr> ::= <symbol>                             (1)
108           <symbol> '=' <symbol>                (2)
109           <symbol> '!=' <symbol>               (3)
110           '(' <expr> ')'                       (4)
111           '!' <expr>                           (5)
112           <expr> '||' <expr>                   (6)
113           <expr> '&&' <expr>                   (7)
114
115Expressions are listed in decreasing order of precedence.
116
117(1) Convert the symbol into an expression. Boolean and tristate symbols
118    are simply converted into the respective expression values. All
119    other symbol types result in 'n'.
120(2) If the values of both symbols are equal, it returns 'y',
121    otherwise 'n'.
122(3) If the values of both symbols are equal, it returns 'n',
123    otherwise 'y'.
124(4) Returns the value of the expression. Used to override precedence.
125(5) Returns the result of (2-/expr/).
126(6) Returns the result of min(/expr/, /expr/).
127(7) Returns the result of max(/expr/, /expr/).
128
129An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2
130respectively for calculations). A menu entry becomes visible when it's
131expression evaluates to 'm' or 'y'.
132
133There are two type of symbols: constant and nonconstant symbols.
134Nonconstant symbols are the most common ones and are defined with the
135'config' statement. Nonconstant symbols consist entirely of alphanumeric
136characters or underscores.
137Constant symbols are only part of expressions. Constant symbols are
138always surrounded by single or double quotes. Within the quote any
139other character is allowed and the quotes can be escaped using '\'.
140
141Menu structure
142--------------
143
144The position of a menu entry in the tree is determined in two ways. First
145it can be specified explicitely:
146
147menu "Network device support"
148    depends NET
149
150config NETDEVICES
151    ...
152
153endmenu
154
155All entries within the "menu" ... "endmenu" block become a submenu of
156"Network device support". All subentries inherit the dependencies from
157the menu entry, e.g. this means the dependency "NET" is added to the
158dependency list of the config option NETDEVICES.
159
160The other way to generate the menu structure is done by analyzing the
161dependencies. If a menu entry somehow depends on the previous entry, it
162can be made a submenu of it. First the the previous (parent) symbol must
163be part of the dependency list and then one of these two condititions
164must be true:
165- the child entry must become invisible, if the parent is set to 'n'
166- the child entry must only be visible, if the parent is visible
167
168config MODULES
169    bool "Enable loadable module support"
170
171config MODVERSIONS
172    bool "Set version information on all module symbols"
173    depends MODULES
174
175comment "module support disabled"
176    depends !MODULES
177
178MODVERSIONS directly depends on MODULES, this means it's only visible if
179MODULES is different from 'n'. The comment on the other hand is always
180visible when MODULES it's visible (the (empty) dependency of MODULES is
181also part of the comment dependencies).
182
183
184Kconfig syntax
185--------------
186
187The configuration file describes a series of menu entries, where every
188line starts with a keyword (except help texts). The following keywords
189end a menu entry:
190- config
191- choice/endchoice
192- comment
193- menu/endmenu
194- if/endif
195- source
196The first four also start the definition of a menu entry.
197
198config:
199
200    "config" <symbol>
201    <config options>
202
203This defines a config symbol <symbol> and accepts any of above
204attributes as options.
205
206choices:
207
208    "choice"
209    <choice options>
210    <choice block>
211    "endchoice"
212
213This defines a choice group and accepts any of above attributes as
214options. A choice can only be of type bool or tristate, while a boolean
215choice only allows a single config entry to be selected, a tristate
216choice also allows any number of config entries to be set to 'm'. This
217can be used if multiple drivers for a single hardware exists and only a
218single driver can be compiled/loaded into the kernel, but all drivers
219can be compiled as modules.
220A choice accepts another option "optional", which allows to set the
221choice to 'n' and no entry needs to be selected.
222
223comment:
224
225    "comment" <prompt>
226    <comment options>
227
228This defines a comment which is displayed to the user during the
229configuration process and is also echoed to the output files. The only
230possible options are dependencies.
231
232menu:
233
234    "menu" <prompt>
235    <menu options>
236    <menu block>
237    "endmenu"
238
239This defines a menu block, see "Menu structure" above for more
240information. The only possible options are dependencies.
241
242if:
243
244    "if" <expr>
245    <if block>
246    "endif"
247
248This defines an if block. The dependency expression <expr> is appended
249to all enclosed menu entries.
250
251source:
252
253    "source" <prompt>
254
255This reads the specified configuration file. This file is always parsed.
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