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b3a939367f
Updating the documentation to reflect that multiple directories can now be specified for BR2_GLOBAL_PATCH_DIR. Along with giving an example use case of how to use multiple global patch directories. [Thomas: fix minor typo mentionned by Thomas De Schampheleire.] Signed-off-by: Ryan Barnett <rjbarnet@rockwellcollins.com> Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com> Cc: Arnout Vandecappelle <arnout@mind.be> Reviewed-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
155 lines
4.8 KiB
Plaintext
155 lines
4.8 KiB
Plaintext
// -*- mode:doc; -*-
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// vim: set syntax=asciidoc:
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[[patch-policy]]
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Patching a package
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------------------
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While integrating a new package or updating an existing one, it may be
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necessary to patch the source of the software to get it cross-built within
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Buildroot.
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Buildroot offers an infrastructure to automatically handle this during
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the builds. It supports three ways of applying patch sets: downloaded patches,
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patches supplied within buildroot and patches located in a user-defined
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global patch directory.
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Providing patches
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~~~~~~~~~~~~~~~~~
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Downloaded
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^^^^^^^^^^
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If it is necessary to apply a patch that is available for download, then add it
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to the +<packagename>_PATCH+ variable. It is downloaded from the same site
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as the package itself. It can be a single patch, or a tarball containing a
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patch series.
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This method is typically used for packages from Debian.
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Within Buildroot
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^^^^^^^^^^^^^^^^
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Most patches are provided within Buildroot, in the package
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directory; these typically aim to fix cross-compilation, libc support,
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or other such issues.
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These patch files should be named +<packagename>-<number>-<description>.patch+.
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A +series+ file, as used by +quilt+, may also be added in the
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package directory. In that case, the +series+ file defines the patch
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application order.
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.Notes
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- The patch files coming with Buildroot should not contain any package version
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reference in their filename.
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- The field +<number>+ in the patch file name refers to the 'apply order'.
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Global patch directory
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^^^^^^^^^^^^^^^^^^^^^^
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The +BR2_GLOBAL_PATCH_DIR+ configuration file option can be
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used to specify a space separated list of one or more directories
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containing global package patches. See xref:packages-custom[] for
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details.
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[[patch-apply-order]]
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How patches are applied
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~~~~~~~~~~~~~~~~~~~~~~~
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. Run the +<packagename>_PRE_PATCH_HOOKS+ commands if defined;
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. Cleanup the build directory, removing any existing +*.rej+ files;
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. If +<packagename>_PATCH+ is defined, then patches from these
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tarballs are applied;
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. If there are some +*.patch+ files in the package's Buildroot
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directory or in a package subdirectory named +<packageversion>+,
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then:
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+
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* If a +series+ file exists in the package directory, then patches are
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applied according to the +series+ file;
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+
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* Otherwise, patch files matching +<packagename>-*.patch+
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are applied in alphabetical order.
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So, to ensure they are applied in the right order, it is highly
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recommended to name the patch files like this:
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+<packagename>-<number>-<description>.patch+, where +<number>+
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refers to the 'apply order'.
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. If +BR2_GLOBAL_PATCH_DIR+ is defined, the directories will be
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enumerated in the order they are specified. The patches are applied
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as described in the previous step.
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. Run the +<packagename>_POST_PATCH_HOOKS+ commands if defined.
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If something goes wrong in the steps _3_ or _4_, then the build fails.
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Format and licensing of the package patches
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Patches are released under the same license as the software that is
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modified.
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A message explaining what the patch does, and why it is needed, should
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be added in the header commentary of the patch.
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You should add a +Signed-off-by+ statement in the header of the each
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patch to help with keeping track of the changes and to certify that the
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patch is released under the same license as the software that is modified.
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If the software is under version control, it is recommended to use the
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upstream SCM software to generate the patch set.
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Otherwise, concatenate the header with the output of the
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+diff -purN package-version.orig/ package-version/+ command.
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At the end, the patch should look like:
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---------------
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configure.ac: add C++ support test
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Signed-off-by: John Doe <john.doe@noname.org>
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--- configure.ac.orig
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+++ configure.ac
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@@ -40,2 +40,12 @@
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AC_PROG_MAKE_SET
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+
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+AC_CACHE_CHECK([whether the C++ compiler works],
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+ [rw_cv_prog_cxx_works],
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+ [AC_LANG_PUSH([C++])
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+ AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
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+ [rw_cv_prog_cxx_works=yes],
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+ [rw_cv_prog_cxx_works=no])
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+ AC_LANG_POP([C++])])
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+
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+AM_CONDITIONAL([CXX_WORKS], [test "x$rw_cv_prog_cxx_works" = "xyes"])
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---------------
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Integrating patches found on the Web
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When integrating a patch of which you are not the author, you have to
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add a few things in the header of the patch itself.
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Depending on whether the patch has been obtained from the project
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repository itself, or from somewhere on the web, add one of the
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following tags:
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---------------
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Backported from: <some commit id>
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---------------
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or
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---------------
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Fetch from: <some url>
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---------------
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It is also sensible to add a few words about any changes to the patch
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that may have been necessary.
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