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Some users of kconfig need some packages to be built before their
kconfig infra be used.
For example, the linux kernel, starting with 4.16, needs flex and bison
to generate the parser code. Furthermore, starting with 4.18, it will
also need the cross-compiler before parsing the kconfig stuff, because
that calls the compiler to check its features.
Currently, this is broken, even the flex/bison ones, even though they
are listed, because there is no way to define dependencie that are
guaranteed before the (visual) configurators. For example:
$ make distclean
$ make menuconfig
--> enable the linux kernel, choose a defconfig, save, exit
$ make linux-menuconfig
[...]
HOSTCC scripts/basic/fixdep
HOSTCC scripts/kconfig/conf.o
YACC scripts/kconfig/zconf.tab.c
/bin/sh: bison: command not found
LEX scripts/kconfig/zconf.lex.c
scripts/Makefile.lib:196: recipe for target 'scripts/kconfig/zconf.tab.c' failed
make[3]: *** [scripts/kconfig/zconf.tab.c] Error 127
make[3]: *** Waiting for unfinished jobs....
/bin/sh: flex: command not found
scripts/Makefile.lib:188: recipe for target 'scripts/kconfig/zconf.lex.c' failed
make[3]: *** [scripts/kconfig/zconf.lex.c] Error 127
Makefile:528: recipe for target 'rpc_defconfig' failed
make[2]: *** [rpc_defconfig] Error 2
linux/linux.mk:511: recipe for target '/home/ymorin/dev/buildroot/buildroot/output/build/linux-4.17.11/.config' failed
make[1]: *** [/home/ymorin/dev/buildroot/buildroot/output/build/linux-4.17.11/.config] Error 2
Makefile:79: recipe for target '_all' failed
make: *** [_all] Error 2
So, we introduce a new type of dependencies for kconfig-based packages,
that are guaranteed to be built and installed before the (visual)
configurators are called.
Since those dependencies are phony targets and therefore always out of
date, a normal dependency would cause the .config target to be rebuilt
on each invocation of make. So we use an order-only pre-requisite, like
is done for the patch dependency.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Jan Kundrát <jan.kundrat@cesnet.cz>
Tested-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
88 lines
3.8 KiB
Plaintext
88 lines
3.8 KiB
Plaintext
// -*- mode:doc; -*-
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// vim: set syntax=asciidoc:
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=== Infrastructure for packages using kconfig for configuration files
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A popular way for a software package to handle user-specified
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configuration is +kconfig+. Among others, it is used by the Linux
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kernel, Busybox, and Buildroot itself. The presence of a .config file
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and a +menuconfig+ target are two well-known symptoms of kconfig being
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used.
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Buildroot features an infrastructure for packages that use kconfig for
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their configuration. This infrastructure provides the necessary logic to
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expose the package's +menuconfig+ target as +foo-menuconfig+ in
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Buildroot, and to handle the copying back and forth of the configuration
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file in a correct way.
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The +kconfig-package+ infrastructure is based on the +generic-package+
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infrastructure. All variables supported by +generic-package+ are
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available in +kconfig-package+ as well. See
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xref:generic-package-reference[] for more details.
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In order to use the +kconfig-package+ infrastructure for a Buildroot
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package, the minimally required lines in the +.mk+ file, in addition to
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the variables required by the +generic-package+ infrastructure, are:
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------------------------------
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FOO_KCONFIG_FILE = reference-to-source-configuration-file
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$(eval $(kconfig-package))
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------------------------------
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This snippet creates the following make targets:
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* +foo-menuconfig+, which calls the package's +menuconfig+ target
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* +foo-update-config+, which copies the configuration back to the
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source configuration file. It is not possible to use this target
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when fragment files are set.
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* +foo-update-defconfig+, which copies the configuration back to the
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source configuration file. The configuration file will only list the
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options that differ from the default values. It is not possible to
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use this target when fragment files are set.
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and ensures that the source configuration file is copied to the build
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directory at the right moment.
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There are two options to specify a configuration file to use, either
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+FOO_KCONFIG_FILE+ (as in the example, above) or +FOO_KCONFIG_DEFCONFIG+.
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It is mandatory to provide either, but not both:
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* +FOO_KCONFIG_FILE+ specifies the path to a defconfig or full-config file
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to be used to configure the package.
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* +FOO_KCONFIG_DEFCONFIG+ specifies the defconfig 'make' rule to call to
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configure the package.
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In addition to these minimally required lines, several optional variables can
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be set to suit the needs of the package under consideration:
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* +FOO_KCONFIG_EDITORS+: a space-separated list of kconfig editors to
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support, for example 'menuconfig xconfig'. By default, 'menuconfig'.
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* +FOO_KCONFIG_FRAGMENT_FILES+: a space-separated list of configuration
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fragment files that are merged to the main configuration file.
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Fragment files are typically used when there is a desire to stay in sync
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with an upstream (def)config file, with some minor modifications.
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* +FOO_KCONFIG_OPTS+: extra options to pass when calling the kconfig
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editors. This may need to include '$(FOO_MAKE_OPTS)', for example. By
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default, empty.
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* +FOO_KCONFIG_FIXUP_CMDS+: a list of shell commands needed to fixup the
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configuration file after copying it or running a kconfig editor. Such
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commands may be needed to ensure a configuration consistent with other
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configuration of Buildroot, for example. By default, empty.
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* +FOO_KCONFIG_DOTCONFIG+: path (with filename) of the +.config+ file,
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relative to the package source tree. The default, +.config+, should
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be well suited for all packages that use the standard kconfig
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infrastructure as inherited from the Linux kernel; some packages use
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a derivative of kconfig that use a different location.
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* +FOO_KCONFIG_DEPENDENCIES+: the list of packages (most probably, host
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packages) that need to be built before this package's kconfig is
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interpreted. Seldom used. By default, empty.
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