Linux Kernel Architecture

Mauerer runapp02.tex V2 - 09/04/2008 6:09pm Page 1148

Appendix B: Working with the Source Code

wherestringis the name of the menu. All entries betweenmenuandendmenuare interpreted as subitems

of the menu and automatically inherit the dependencies of the menu item (these are added to the existing

dependencies of the subitems).

The keywordmenuconfigis used to define a configuration symbol and a submenu together. Instead of

writing this:

menu "Bit bucket compression support"

config BIT_BUCKET_ZLIB

tristate "Bit bucket compression support"

you can also specify the shorter form as follows:

menuconfig BIT_BUCKET_ZLIB

tristate "Bit bucket compression support"

Another keyword,mainmenu, may occur only at the top of the configuration hierarchy (and then once

only) to specify a title for the entire hierarchy. The entry is therefore used only inarch/arch/Kconfig

because these files represent the starting point of theconfiguration hierarchy. For example, the version

for Sparc64 processors includes the following entry:

mainmenu "Linux/UltraSPARC Kernel Configuration"

ConfigurationOptions

Configuration options are introduced by the keywordconfigthat must be followed by a configuration

symbol.

config <symbol>

<type-name> "Description"

<attributes>

The type name indicates the option type. As mentioned earlier, the tristate type has one of the following

states:y,n,orm. Additional option types include the following:

❑ boolpermits a Boolean query that returns eitheryorn— in other words, the entry may be

selected or not.

❑ stringqueries a string.

❑ hexandintegerread hexadecimal and decimal numbers respectively.

The following syntax can be used instead of the type name:

config <symbol>

<type-name>

prompt "Description"

In functional terms, this is identical to the previous, shorter alternative.