// -*- mode:doc; -*- // vim: set syntax=asciidoc: === Package directory First of all, create a directory under the +package+ directory for your software, for example +libfoo+. Some packages have been grouped by topic in a sub-directory: +x11r7+, +qt5+ and +gstreamer+. If your package fits in one of these categories, then create your package directory in these. New subdirectories are discouraged, however. === Config files For the package to be displayed in the configuration tool, you need to create a Config file in your package directory. There are two types: +Config.in+ and +Config.in.host+. ==== +Config.in+ file For packages used on the target, create a file named +Config.in+. This file will contain the option descriptions related to our +libfoo+ software that will be used and displayed in the configuration tool. It should basically contain: --------------------------- config BR2_PACKAGE_LIBFOO bool "libfoo" help This is a comment that explains what libfoo is. The help text should be wrapped. http://foosoftware.org/libfoo/ --------------------------- The +bool+ line, +help+ line and other metadata information about the configuration option must be indented with one tab. The help text itself should be indented with one tab and two spaces, lines should be wrapped to fit 72 columns, where tab counts for 8, so 62 characters in the text itself. The help text must mention the upstream URL of the project after an empty line. As a convention specific to Buildroot, the ordering of the attributes is as follows: 1. The type of option: +bool+, +string+... with the prompt 2. If needed, the +default+ value(s) 3. Any dependencies on the target in +depends on+ form 4. Any dependencies on the toolchain in +depends on+ form 5. Any dependencies on other packages in +depends on+ form 6. Any dependency of the +select+ form 7. The help keyword and help text. You can add other sub-options into a +if BR2_PACKAGE_LIBFOO...endif+ statement to configure particular things in your software. You can look at examples in other packages. The syntax of the +Config.in+ file is the same as the one for the kernel Kconfig file. The documentation for this syntax is available at http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt[] Finally you have to add your new +libfoo/Config.in+ to +package/Config.in+ (or in a category subdirectory if you decided to put your package in one of the existing categories). The files included there are 'sorted alphabetically' per category and are 'NOT' supposed to contain anything but the 'bare' name of the package. -------------------------- source "package/libfoo/Config.in" -------------------------- ==== +Config.in.host+ file Some packages also need to be built for the host system. There are two options here: * The host package is only required to satisfy build-time dependencies of one or more target packages. In this case, add +host-foo+ to the target package's +BAR_DEPENDENCIES+ variable. No +Config.in.host+ file should be created. * The host package should be explicitly selectable by the user from the configuration menu. In this case, create a +Config.in.host+ file for that host package: + --------------------------- config BR2_PACKAGE_HOST_FOO bool "host foo" help This is a comment that explains what foo for the host is. http://foosoftware.org/foo/ --------------------------- + The same coding style and options as for the +Config.in+ file are valid. + Finally you have to add your new +libfoo/Config.in.host+ to +package/Config.in.host+. The files included there are 'sorted alphabetically' and are 'NOT' supposed to contain anything but the 'bare' name of the package. + -------------------------- source "package/foo/Config.in.host" -------------------------- + The host package will then be available from the +Host utilities+ menu. [[depends-on-vs-select]] ==== Choosing +depends on+ or +select+ The +Config.in+ file of your package must also ensure that dependencies are enabled. Typically, Buildroot uses the following rules: * Use a +select+ type of dependency for dependencies on libraries. These dependencies are generally not obvious and it therefore make sense to have the kconfig system ensure that the dependencies are selected. For example, the _libgtk2_ package uses +select BR2_PACKAGE_LIBGLIB2+ to make sure this library is also enabled. The +select+ keyword expresses the dependency with a backward semantic. * Use a +depends on+ type of dependency when the user really needs to be aware of the dependency. Typically, Buildroot uses this type of dependency for dependencies on target architecture, MMU support and toolchain options (see xref:dependencies-target-toolchain-options[]), or for dependencies on "big" things, such as the X.org system. The +depends on+ keyword expresses the dependency with a forward semantic. .Note The current problem with the _kconfig_ language is that these two dependency semantics are not internally linked. Therefore, it may be possible to select a package, whom one of its dependencies/requirement is not met. An example illustrates both the usage of +select+ and +depends on+. -------------------------- config BR2_PACKAGE_RRDTOOL bool "rrdtool" depends on BR2_USE_WCHAR select BR2_PACKAGE_FREETYPE select BR2_PACKAGE_LIBART select BR2_PACKAGE_LIBPNG select BR2_PACKAGE_ZLIB help RRDtool is the OpenSource industry standard, high performance data logging and graphing system for time series data. http://oss.oetiker.ch/rrdtool/ comment "rrdtool needs a toolchain w/ wchar" depends on !BR2_USE_WCHAR -------------------------- Note that these two dependency types are only transitive with the dependencies of the same kind. This means, in the following example: -------------------------- config BR2_PACKAGE_A bool "Package A" config BR2_PACKAGE_B bool "Package B" depends on BR2_PACKAGE_A config BR2_PACKAGE_C bool "Package C" depends on BR2_PACKAGE_B config BR2_PACKAGE_D bool "Package D" select BR2_PACKAGE_B config BR2_PACKAGE_E bool "Package E" select BR2_PACKAGE_D -------------------------- * Selecting +Package C+ will be visible if +Package B+ has been selected, which in turn is only visible if +Package A+ has been selected. * Selecting +Package E+ will select +Package D+, which will select +Package B+, it will not check for the dependencies of +Package B+, so it will not select +Package A+. * Since +Package B+ is selected but +Package A+ is not, this violates the dependency of +Package B+ on +Package A+. Therefore, in such a situation, the transitive dependency has to be added explicitly: -------------------------- config BR2_PACKAGE_D bool "Package D" depends on BR2_PACKAGE_A select BR2_PACKAGE_B config BR2_PACKAGE_E bool "Package E" depends on BR2_PACKAGE_A select BR2_PACKAGE_D -------------------------- Overall, for package library dependencies, +select+ should be preferred. Note that such dependencies will ensure that the dependency option is also enabled, but not necessarily built before your package. To do so, the dependency also needs to be expressed in the +.mk+ file of the package. Further formatting details: see xref:writing-rules-config-in[the coding style]. [[dependencies-target-toolchain-options]] ==== Dependencies on target and toolchain options Many packages depend on certain options of the toolchain: the choice of C library, C++ support, thread support, RPC support, wchar support, or dynamic library support. Some packages can only be built on certain target architectures, or if an MMU is available in the processor. These dependencies have to be expressed with the appropriate 'depends on' statements in the Config.in file. Additionally, for dependencies on toolchain options, a +comment+ should be displayed when the option is not enabled, so that the user knows why the package is not available. Dependencies on target architecture or MMU support should not be made visible in a comment: since it is unlikely that the user can freely choose another target, it makes little sense to show these dependencies explicitly. The +comment+ should only be visible if the +config+ option itself would be visible when the toolchain option dependencies are met. This means that all other dependencies of the package (including dependencies on target architecture and MMU support) have to be repeated on the +comment+ definition. To keep it clear, the +depends on+ statement for these non-toolchain option should be kept separate from the +depends on+ statement for the toolchain options. If there is a dependency on a config option in that same file (typically the main package) it is preferable to have a global +if ... endif+ construct rather than repeating the +depends on+ statement on the comment and other config options. The general format of a dependency +comment+ for package foo is: -------------------------- foo needs a toolchain w/ featA, featB, featC -------------------------- for example: -------------------------- mpd needs a toolchain w/ C++, threads, wchar -------------------------- or -------------------------- crda needs a toolchain w/ threads -------------------------- Note that this text is kept brief on purpose, so that it will fit on a 80-character terminal. The rest of this section enumerates the different target and toolchain options, the corresponding config symbols to depend on, and the text to use in the comment. * Target architecture ** Dependency symbol: +BR2_powerpc+, +BR2_mips+, ... (see +arch/Config.in+) ** Comment string: no comment to be added * MMU support ** Dependency symbol: +BR2_USE_MMU+ ** Comment string: no comment to be added * Gcc +__sync_*+ built-ins used for atomic operations. They are available in variants operating on 1 byte, 2 bytes, 4 bytes and 8 bytes. Since different architectures support atomic operations on different sizes, one dependency symbol is available for each size: ** Dependency symbol: +BR2_TOOLCHAIN_HAS_SYNC_1+ for 1 byte, +BR2_TOOLCHAIN_HAS_SYNC_2+ for 2 bytes, +BR2_TOOLCHAIN_HAS_SYNC_4+ for 4 bytes, +BR2_TOOLCHAIN_HAS_SYNC_8+ for 8 bytes. ** Comment string: no comment to be added * Gcc +__atomic_*+ built-ins used for atomic operations. ** Dependency symbol: +BR2_TOOLCHAIN_HAS_ATOMIC+. ** Comment string: no comment to be added * Kernel headers ** Dependency symbol: +BR2_TOOLCHAIN_HEADERS_AT_LEAST_X_Y+, (replace +X_Y+ with the proper version, see +toolchain/Config.in+) ** Comment string: +headers >= X.Y+ and/or `headers <= X.Y` (replace +X.Y+ with the proper version) * GCC version ** Dependency symbol: +BR2_TOOLCHAIN_GCC_AT_LEAST_X_Y+, (replace +X_Y+ with the proper version, see +toolchain/Config.in+) ** Comment string: +gcc >= X.Y+ and/or `gcc <= X.Y` (replace +X.Y+ with the proper version) * Host GCC version ** Dependency symbol: +BR2_HOST_GCC_AT_LEAST_X_Y+, (replace +X_Y+ with the proper version, see +Config.in+) ** Comment string: no comment to be added ** Note that it is usually not the package itself that has a minimum host GCC version, but rather a host-package on which it depends. * C library ** Dependency symbol: +BR2_TOOLCHAIN_USES_GLIBC+, +BR2_TOOLCHAIN_USES_MUSL+, +BR2_TOOLCHAIN_USES_UCLIBC+ ** Comment string: for the C library, a slightly different comment text is used: +foo needs a glibc toolchain+, or `foo needs a glibc toolchain w/ C++` * C++ support ** Dependency symbol: +BR2_INSTALL_LIBSTDCPP+ ** Comment string: `C++` * D support ** Dependency symbol: +BR2_TOOLCHAIN_HAS_DLANG+ ** Comment string: `Dlang` * Fortran support ** Dependency symbol: +BR2_TOOLCHAIN_HAS_FORTRAN+ ** Comment string: `fortran` * thread support ** Dependency symbol: +BR2_TOOLCHAIN_HAS_THREADS+ ** Comment string: +threads+ (unless +BR2_TOOLCHAIN_HAS_THREADS_NPTL+ is also needed, in which case, specifying only +NPTL+ is sufficient) * NPTL thread support ** Dependency symbol: +BR2_TOOLCHAIN_HAS_THREADS_NPTL+ ** Comment string: +NPTL+ * RPC support ** Dependency symbol: +BR2_TOOLCHAIN_HAS_NATIVE_RPC+ ** Comment string: +RPC+ * wchar support ** Dependency symbol: +BR2_USE_WCHAR+ ** Comment string: +wchar+ * dynamic library ** Dependency symbol: +!BR2_STATIC_LIBS+ ** Comment string: +dynamic library+ ==== Dependencies on a Linux kernel built by buildroot Some packages need a Linux kernel to be built by buildroot. These are typically kernel modules or firmware. A comment should be added in the Config.in file to express this dependency, similar to dependencies on toolchain options. The general format is: -------------------------- foo needs a Linux kernel to be built -------------------------- If there is a dependency on both toolchain options and the Linux kernel, use this format: -------------------------- foo needs a toolchain w/ featA, featB, featC and a Linux kernel to be built -------------------------- ==== Dependencies on udev /dev management If a package needs udev /dev management, it should depend on symbol +BR2_PACKAGE_HAS_UDEV+, and the following comment should be added: -------------------------- foo needs udev /dev management -------------------------- If there is a dependency on both toolchain options and udev /dev management, use this format: -------------------------- foo needs udev /dev management and a toolchain w/ featA, featB, featC -------------------------- ==== Dependencies on features provided by virtual packages Some features can be provided by more than one package, such as the openGL libraries. See xref:virtual-package-tutorial[] for more on the virtual packages. === The +.mk+ file [[adding-packages-mk]] Finally, here's the hardest part. Create a file named +libfoo.mk+. It describes how the package should be downloaded, configured, built, installed, etc. Depending on the package type, the +.mk+ file must be written in a different way, using different infrastructures: * *Makefiles for generic packages* (not using autotools or CMake): These are based on an infrastructure similar to the one used for autotools-based packages, but require a little more work from the developer. They specify what should be done for the configuration, compilation and installation of the package. This infrastructure must be used for all packages that do not use the autotools as their build system. In the future, other specialized infrastructures might be written for other build systems. We cover them through in a xref:generic-package-tutorial[tutorial] and a xref:generic-package-reference[reference]. * *Makefiles for autotools-based software* (autoconf, automake, etc.): We provide a dedicated infrastructure for such packages, since autotools is a very common build system. This infrastructure 'must' be used for new packages that rely on the autotools as their build system. We cover them through a xref:autotools-package-tutorial[tutorial] and xref:autotools-package-reference[reference]. * *Makefiles for cmake-based software*: We provide a dedicated infrastructure for such packages, as CMake is a more and more commonly used build system and has a standardized behaviour. This infrastructure 'must' be used for new packages that rely on CMake. We cover them through a xref:cmake-package-tutorial[tutorial] and xref:cmake-package-reference[reference]. * *Makefiles for Python modules*: We have a dedicated infrastructure for Python modules that use the +distutils+, +flit+, +pep517+ or +setuptools+ mechanisms. We cover them through a xref:python-package-tutorial[tutorial] and a xref:python-package-reference[reference]. * *Makefiles for Lua modules*: We have a dedicated infrastructure for Lua modules available through the LuaRocks web site. We cover them through a xref:luarocks-package-tutorial[tutorial] and a xref:luarocks-package-reference[reference]. Further formatting details: see xref:writing-rules-mk[the writing rules]. [[adding-packages-hash]] === The +.hash+ file When possible, you must add a third file, named +libfoo.hash+, that contains the hashes of the downloaded files for the +libfoo+ package. The only reason for not adding a +.hash+ file is when hash checking is not possible due to how the package is downloaded. When a package has a version selection choice, then the hash file may be stored in a subdirectory named after the version, e.g. +package/libfoo/1.2.3/libfoo.hash+. This is especially important if the different versions have different licensing terms, but they are stored in the same file. Otherwise, the hash file should stay in the package's directory. The hashes stored in that file are used to validate the integrity of the downloaded files and of the license files. The format of this file is one line for each file for which to check the hash, each line with the following three fields separated by two spaces: * the type of hash, one of: ** +md5+, +sha1+, +sha224+, +sha256+, +sha384+, +sha512+ * the hash of the file: ** for +md5+, 32 hexadecimal characters ** for +sha1+, 40 hexadecimal characters ** for +sha224+, 56 hexadecimal characters ** for +sha256+, 64 hexadecimal characters ** for +sha384+, 96 hexadecimal characters ** for +sha512+, 128 hexadecimal characters * the name of the file: ** for a source archive: the basename of the file, without any directory component, ** for a license file: the path as it appears in +FOO_LICENSE_FILES+. Lines starting with a +#+ sign are considered comments, and ignored. Empty lines are ignored. There can be more than one hash for a single file, each on its own line. In this case, all hashes must match. .Note Ideally, the hashes stored in this file should match the hashes published by upstream, e.g. on their website, in the e-mail announcement... If upstream provides more than one type of hash (e.g. +sha1+ and +sha512+), then it is best to add all those hashes in the +.hash+ file. If upstream does not provide any hash, or only provides an +md5+ hash, then compute at least one strong hash yourself (preferably +sha256+, but not +md5+), and mention this in a comment line above the hashes. .Note The hashes for license files are used to detect a license change when a package version is bumped. The hashes are checked during the make legal-info target run. For a package with multiple versions (like Qt5), create the hash file in a subdirectory ++ of that package (see also xref:patch-apply-order[]). The example below defines a +sha1+ and a +sha256+ published by upstream for the main +libfoo-1.2.3.tar.bz2+ tarball, an +md5+ from upstream and a locally-computed +sha256+ hashes for a binary blob, a +sha256+ for a downloaded patch, and an archive with no hash: ---- # Hashes from: http://www.foosoftware.org/download/libfoo-1.2.3.tar.bz2.{sha1,sha256}: sha1 486fb55c3efa71148fe07895fd713ea3a5ae343a libfoo-1.2.3.tar.bz2 sha256 efc8103cc3bcb06bda6a781532d12701eb081ad83e8f90004b39ab81b65d4369 libfoo-1.2.3.tar.bz2 # md5 from: http://www.foosoftware.org/download/libfoo-1.2.3.tar.bz2.md5, sha256 locally computed: md5 2d608f3c318c6b7557d551a5a09314f03452f1a1 libfoo-data.bin sha256 01ba4719c80b6fe911b091a7c05124b64eeece964e09c058ef8f9805daca546b libfoo-data.bin # Locally computed: sha256 ff52101fb90bbfc3fe9475e425688c660f46216d7e751c4bbdb1dc85cdccacb9 libfoo-fix-blabla.patch # Hash for license files: sha256 a45a845012742796534f7e91fe623262ccfb99460a2bd04015bd28d66fba95b8 COPYING sha256 01b1f9f2c8ee648a7a596a1abe8aa4ed7899b1c9e5551bda06da6e422b04aa55 doc/COPYING.LGPL ---- If the +.hash+ file is present, and it contains one or more hashes for a downloaded file, the hash(es) computed by Buildroot (after download) must match the hash(es) stored in the +.hash+ file. If one or more hashes do not match, Buildroot considers this an error, deletes the downloaded file, and aborts. If the +.hash+ file is present, but it does not contain a hash for a downloaded file, Buildroot considers this an error and aborts. However, the downloaded file is left in the download directory since this typically indicates that the +.hash+ file is wrong but the downloaded file is probably OK. Hashes are currently checked for files fetched from http/ftp servers, Git repositories, files copied using scp and local files. Hashes are not checked for other version control systems (such as Subversion, CVS, etc.) because Buildroot currently does not generate reproducible tarballs when source code is fetched from such version control systems. Hashes should only be added in +.hash+ files for files that are guaranteed to be stable. For example, patches auto-generated by Github are not guaranteed to be stable, and therefore their hashes can change over time. Such patches should not be downloaded, and instead be added locally to the package folder. If the +.hash+ file is missing, then no check is done at all. [[adding-packages-start-script]] === The +SNNfoo+ start script Packages that provide a system daemon usually need to be started somehow at boot. Buildroot comes with support for several init systems, some are considered tier one (see xref:init-system[]), while others are also available but do not have the same level of integration. Ideally, all packages providing a system daemon should provide a start script for BusyBox/SysV init and a systemd unit file. For consistency, the start script must follow the style and composition as shown in the reference: +package/busybox/S01syslogd+. An annotated example of this style is shown below. There is no specific coding style for systemd unit files, but if a package comes with its own unit file, that is preferred over a buildroot specific one, if it is compatible with buildroot. The name of the start script is composed of the +SNN+ and the daemon name. The +NN+ is the start order number which needs to be carefully chosen. For example, a program that requires networking to be up should not start before +S40network+. The scripts are started in alphabetical order, so +S01syslogd+ starts before +S01watchdogd+, and +S02sysctl+ start thereafter. ------------------------------ 01: #!/bin/sh 02: 03: DAEMON="syslogd" 04: PIDFILE="/var/run/$DAEMON.pid" 05: 06: SYSLOGD_ARGS="" 07: 08: # shellcheck source=/dev/null 09: [ -r "/etc/default/$DAEMON" ] && . "/etc/default/$DAEMON" 10: 11: # BusyBox' syslogd does not create a pidfile, so pass "-n" in the command line 12: # and use "-m" to instruct start-stop-daemon to create one. 13: start() { 14: printf 'Starting %s: ' "$DAEMON" 15: # shellcheck disable=SC2086 # we need the word splitting 16: start-stop-daemon -b -m -S -q -p "$PIDFILE" -x "/sbin/$DAEMON" \ 17: -- -n $SYSLOGD_ARGS 18: status=$? 19: if [ "$status" -eq 0 ]; then 20: echo "OK" 21: else 22: echo "FAIL" 23: fi 24: return "$status" 25: } 26: 27: stop() { 28: printf 'Stopping %s: ' "$DAEMON" 29: start-stop-daemon -K -q -p "$PIDFILE" 30: status=$? 31: if [ "$status" -eq 0 ]; then 32: rm -f "$PIDFILE" 33: echo "OK" 34: else 35: echo "FAIL" 36: fi 37: return "$status" 38: } 39: 40: restart() { 41: stop 42: sleep 1 43: start 44: } 45: 46: case "$1" in 47: start|stop|restart) 48: "$1";; 49: reload) 50: # Restart, since there is no true "reload" feature. 51: restart;; 52: *) 53: echo "Usage: $0 {start|stop|restart|reload}" 54: exit 1 55: esac ------------------------------ *Note:* programs that support reloading their configuration in some fashion (+SIGHUP+) should provide a +reload()+ function similar to +stop()+. The +start-stop-daemon+ supports +-K -s HUP+ for this. It is recommended to always append +-x "/sbin/$DAEMON"+ to all the +start-stop-daemon+ commands to ensure signals are set to a PID that matches +$DAEMON+. Both start scripts and unit files can source command line arguments from +/etc/default/foo+, in general, if such a file does not exist it should not block the start of the daemon, unless there is some site specirfic command line argument the daemon requires to start. For start scripts a +FOO_ARGS="-s -o -m -e -args"+ can be defined to a default value in and the user can override this from +/etc/default/foo+.