c7d71b707d
Currently, as Thomas pointed out [0], the help for kconfig packages is
not consistently used and handled by the different packages.
This commit introduces a generic help text for kconfig packages, that is
based on what the package declares:
- the list of kconfig editors it supports;
- whether it is possible to save back the configuration (impossible if
the package uses an in-tree defconfig file);
- whether the package actually supports (loading and saving) defconfig
files, by introducing a new variable a package can set if it does
not (only busybox is known to be in that case).
That new help helper is only used if the package does not already define
its own help, to be consistent with what we do for other _CMDS.
[0] http://lists.busybox.net/pipermail/buildroot/2021-July/313570.html
Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
97 lines
4.2 KiB
Plaintext
97 lines
4.2 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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* +foo-diff-config+, which outputs the differences between the current
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configuration and the one defined in the Buildroot configuration for
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this kconfig package. The output is useful to identify the
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configuration changes that may have to be propagated to
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configuration fragments for example.
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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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* +FOO_KCONFIG_SUPPORTS_DEFCONFIG+: whether the package's kconfig system
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supports using defconfig files; few packages do not. By default, 'YES'.
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