e95be9a532
While reading this I noticed that the contents of this document list section "3.8 Command line dependency" but it doesn't exist in the document. Signed-off-by: Daniel Walker <dwalker@mvista.com> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
283 lines
9.4 KiB
Plaintext
283 lines
9.4 KiB
Plaintext
Introduction
|
|
------------
|
|
|
|
The configuration database is a collection of configuration options
|
|
organized in a tree structure:
|
|
|
|
+- Code maturity level options
|
|
| +- Prompt for development and/or incomplete code/drivers
|
|
+- General setup
|
|
| +- Networking support
|
|
| +- System V IPC
|
|
| +- BSD Process Accounting
|
|
| +- Sysctl support
|
|
+- Loadable module support
|
|
| +- Enable loadable module support
|
|
| +- Set version information on all module symbols
|
|
| +- Kernel module loader
|
|
+- ...
|
|
|
|
Every entry has its own dependencies. These dependencies are used
|
|
to determine the visibility of an entry. Any child entry is only
|
|
visible if its parent entry is also visible.
|
|
|
|
Menu entries
|
|
------------
|
|
|
|
Most entries define a config option, all other entries help to organize
|
|
them. A single configuration option is defined like this:
|
|
|
|
config MODVERSIONS
|
|
bool "Set version information on all module symbols"
|
|
depends MODULES
|
|
help
|
|
Usually, modules have to be recompiled whenever you switch to a new
|
|
kernel. ...
|
|
|
|
Every line starts with a key word and can be followed by multiple
|
|
arguments. "config" starts a new config entry. The following lines
|
|
define attributes for this config option. Attributes can be the type of
|
|
the config option, input prompt, dependencies, help text and default
|
|
values. A config option can be defined multiple times with the same
|
|
name, but every definition can have only a single input prompt and the
|
|
type must not conflict.
|
|
|
|
Menu attributes
|
|
---------------
|
|
|
|
A menu entry can have a number of attributes. Not all of them are
|
|
applicable everywhere (see syntax).
|
|
|
|
- type definition: "bool"/"tristate"/"string"/"hex"/"int"
|
|
Every config option must have a type. There are only two basic types:
|
|
tristate and string, the other types are based on these two. The type
|
|
definition optionally accepts an input prompt, so these two examples
|
|
are equivalent:
|
|
|
|
bool "Networking support"
|
|
and
|
|
bool
|
|
prompt "Networking support"
|
|
|
|
- input prompt: "prompt" <prompt> ["if" <expr>]
|
|
Every menu entry can have at most one prompt, which is used to display
|
|
to the user. Optionally dependencies only for this prompt can be added
|
|
with "if".
|
|
|
|
- default value: "default" <expr> ["if" <expr>]
|
|
A config option can have any number of default values. If multiple
|
|
default values are visible, only the first defined one is active.
|
|
Default values are not limited to the menu entry where they are
|
|
defined. This means the default can be defined somewhere else or be
|
|
overridden by an earlier definition.
|
|
The default value is only assigned to the config symbol if no other
|
|
value was set by the user (via the input prompt above). If an input
|
|
prompt is visible the default value is presented to the user and can
|
|
be overridden by him.
|
|
Optionally, dependencies only for this default value can be added with
|
|
"if".
|
|
|
|
- dependencies: "depends on"/"requires" <expr>
|
|
This defines a dependency for this menu entry. If multiple
|
|
dependencies are defined, they are connected with '&&'. Dependencies
|
|
are applied to all other options within this menu entry (which also
|
|
accept an "if" expression), so these two examples are equivalent:
|
|
|
|
bool "foo" if BAR
|
|
default y if BAR
|
|
and
|
|
depends on BAR
|
|
bool "foo"
|
|
default y
|
|
|
|
- reverse dependencies: "select" <symbol> ["if" <expr>]
|
|
While normal dependencies reduce the upper limit of a symbol (see
|
|
below), reverse dependencies can be used to force a lower limit of
|
|
another symbol. The value of the current menu symbol is used as the
|
|
minimal value <symbol> can be set to. If <symbol> is selected multiple
|
|
times, the limit is set to the largest selection.
|
|
Reverse dependencies can only be used with boolean or tristate
|
|
symbols.
|
|
|
|
- numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
|
|
This allows to limit the range of possible input values for int
|
|
and hex symbols. The user can only input a value which is larger than
|
|
or equal to the first symbol and smaller than or equal to the second
|
|
symbol.
|
|
|
|
- help text: "help" or "---help---"
|
|
This defines a help text. The end of the help text is determined by
|
|
the indentation level, this means it ends at the first line which has
|
|
a smaller indentation than the first line of the help text.
|
|
"---help---" and "help" do not differ in behaviour, "---help---" is
|
|
used to help visually separate configuration logic from help within
|
|
the file as an aid to developers.
|
|
|
|
|
|
Menu dependencies
|
|
-----------------
|
|
|
|
Dependencies define the visibility of a menu entry and can also reduce
|
|
the input range of tristate symbols. The tristate logic used in the
|
|
expressions uses one more state than normal boolean logic to express the
|
|
module state. Dependency expressions have the following syntax:
|
|
|
|
<expr> ::= <symbol> (1)
|
|
<symbol> '=' <symbol> (2)
|
|
<symbol> '!=' <symbol> (3)
|
|
'(' <expr> ')' (4)
|
|
'!' <expr> (5)
|
|
<expr> '&&' <expr> (6)
|
|
<expr> '||' <expr> (7)
|
|
|
|
Expressions are listed in decreasing order of precedence.
|
|
|
|
(1) Convert the symbol into an expression. Boolean and tristate symbols
|
|
are simply converted into the respective expression values. All
|
|
other symbol types result in 'n'.
|
|
(2) If the values of both symbols are equal, it returns 'y',
|
|
otherwise 'n'.
|
|
(3) If the values of both symbols are equal, it returns 'n',
|
|
otherwise 'y'.
|
|
(4) Returns the value of the expression. Used to override precedence.
|
|
(5) Returns the result of (2-/expr/).
|
|
(6) Returns the result of min(/expr/, /expr/).
|
|
(7) Returns the result of max(/expr/, /expr/).
|
|
|
|
An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2
|
|
respectively for calculations). A menu entry becomes visible when it's
|
|
expression evaluates to 'm' or 'y'.
|
|
|
|
There are two types of symbols: constant and nonconstant symbols.
|
|
Nonconstant symbols are the most common ones and are defined with the
|
|
'config' statement. Nonconstant symbols consist entirely of alphanumeric
|
|
characters or underscores.
|
|
Constant symbols are only part of expressions. Constant symbols are
|
|
always surrounded by single or double quotes. Within the quote, any
|
|
other character is allowed and the quotes can be escaped using '\'.
|
|
|
|
Menu structure
|
|
--------------
|
|
|
|
The position of a menu entry in the tree is determined in two ways. First
|
|
it can be specified explicitly:
|
|
|
|
menu "Network device support"
|
|
depends NET
|
|
|
|
config NETDEVICES
|
|
...
|
|
|
|
endmenu
|
|
|
|
All entries within the "menu" ... "endmenu" block become a submenu of
|
|
"Network device support". All subentries inherit the dependencies from
|
|
the menu entry, e.g. this means the dependency "NET" is added to the
|
|
dependency list of the config option NETDEVICES.
|
|
|
|
The other way to generate the menu structure is done by analyzing the
|
|
dependencies. If a menu entry somehow depends on the previous entry, it
|
|
can be made a submenu of it. First, the previous (parent) symbol must
|
|
be part of the dependency list and then one of these two conditions
|
|
must be true:
|
|
- the child entry must become invisible, if the parent is set to 'n'
|
|
- the child entry must only be visible, if the parent is visible
|
|
|
|
config MODULES
|
|
bool "Enable loadable module support"
|
|
|
|
config MODVERSIONS
|
|
bool "Set version information on all module symbols"
|
|
depends MODULES
|
|
|
|
comment "module support disabled"
|
|
depends !MODULES
|
|
|
|
MODVERSIONS directly depends on MODULES, this means it's only visible if
|
|
MODULES is different from 'n'. The comment on the other hand is always
|
|
visible when MODULES is visible (the (empty) dependency of MODULES is
|
|
also part of the comment dependencies).
|
|
|
|
|
|
Kconfig syntax
|
|
--------------
|
|
|
|
The configuration file describes a series of menu entries, where every
|
|
line starts with a keyword (except help texts). The following keywords
|
|
end a menu entry:
|
|
- config
|
|
- menuconfig
|
|
- choice/endchoice
|
|
- comment
|
|
- menu/endmenu
|
|
- if/endif
|
|
- source
|
|
The first five also start the definition of a menu entry.
|
|
|
|
config:
|
|
|
|
"config" <symbol>
|
|
<config options>
|
|
|
|
This defines a config symbol <symbol> and accepts any of above
|
|
attributes as options.
|
|
|
|
menuconfig:
|
|
"menuconfig" <symbol>
|
|
<config options>
|
|
|
|
This is similar to the simple config entry above, but it also gives a
|
|
hint to front ends, that all suboptions should be displayed as a
|
|
separate list of options.
|
|
|
|
choices:
|
|
|
|
"choice"
|
|
<choice options>
|
|
<choice block>
|
|
"endchoice"
|
|
|
|
This defines a choice group and accepts any of the above attributes as
|
|
options. A choice can only be of type bool or tristate, while a boolean
|
|
choice only allows a single config entry to be selected, a tristate
|
|
choice also allows any number of config entries to be set to 'm'. This
|
|
can be used if multiple drivers for a single hardware exists and only a
|
|
single driver can be compiled/loaded into the kernel, but all drivers
|
|
can be compiled as modules.
|
|
A choice accepts another option "optional", which allows to set the
|
|
choice to 'n' and no entry needs to be selected.
|
|
|
|
comment:
|
|
|
|
"comment" <prompt>
|
|
<comment options>
|
|
|
|
This defines a comment which is displayed to the user during the
|
|
configuration process and is also echoed to the output files. The only
|
|
possible options are dependencies.
|
|
|
|
menu:
|
|
|
|
"menu" <prompt>
|
|
<menu options>
|
|
<menu block>
|
|
"endmenu"
|
|
|
|
This defines a menu block, see "Menu structure" above for more
|
|
information. The only possible options are dependencies.
|
|
|
|
if:
|
|
|
|
"if" <expr>
|
|
<if block>
|
|
"endif"
|
|
|
|
This defines an if block. The dependency expression <expr> is appended
|
|
to all enclosed menu entries.
|
|
|
|
source:
|
|
|
|
"source" <prompt>
|
|
|
|
This reads the specified configuration file. This file is always parsed.
|