manual: update for multiple global patch dirs
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>
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Ryan Barnett
Thomas Petazzoni
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commit
b3a939367f
@ -8,16 +8,90 @@ It is sometimes useful to apply 'extra' patches to packages - over and
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above those provided in Buildroot. This might be used to support custom
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features in a project, for example, or when working on a new architecture.
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The +BR2_GLOBAL_PATCH_DIR+ configuration file option can be
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used to specify a directory containing global package patches.
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The +BR2_GLOBAL_PATCH_DIR+ configuration option can be used to specify
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a space separated list of one or more directories containing package
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patches. By specifying multiple global patch directories, a user could
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implement a layered approach to patches. This could be useful when a
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user has multiple boards that share a common processor architecture.
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It is often the case that a subset of patches for a package need to be
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shared between the different boards a user has. However, each board
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may require specific patches for the package that build on top of the
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common subset of patches.
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For a specific version <packageversion> of a specific package <packagename>,
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patches are applied as follows.
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For a specific version +<packageversion>+ of a specific package
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+<packagename>+, patches are applied from +BR2_GLOBAL_PATCH_DIR+ as
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follows:
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First, the default Buildroot patch set for the package is applied.
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. For every directory - +<global-patch-dir>+ - that exists in
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+BR2_GLOBAL_PATCH_DIR+, a +<package-patch-dir>+ will be determined as
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follows:
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+
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* +<global-patch-dir>/<packagename>/<packageversion>/+ if the
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directory exists.
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+
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* Otherwise, +<global-patch-dir>/<packagename>+ if the directory
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exists.
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If the directory +$(BR2_GLOBAL_PATCH_DIR)/<packagename>/<packageversion>+
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exists, then all +*.patch+ files in the directory will be applied.
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. Patches will then be applied from a +<package-patch-dir>+ as
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follows:
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+
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* If a +series+ file exists in the package directory, then patches are
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applied according to the +series+ file;
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+
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* Otherwise, patch files matching +<packagename>-*.patch+
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are applied in alphabetical order.
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So, to ensure they are applied in the right order, it is highly
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recommended to name the patch files like this:
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+<packagename>-<number>-<description>.patch+, where +<number>+
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refers to the 'apply order'.
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Otherwise, if the directory +$(BR2_GLOBAL_PATCH_DIR)/<packagename>+
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exists, then all +*.patch+ files in the directory will be applied.
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For information about how patches are applied for a package, see
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xref:patch-apply-order[]
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The +BR2_GLOBAL_PATCH_DIR+ option is the preferred method for
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specifying a custom patch directory for packages. It can be used to
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specify a patch directory for any package in buildroot. It should also
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be used in place of the custom patch directory options that are
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available for packages such as U-Boot and Barebox. By doing this, it
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will allow a user to manage their patches from one top-level
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directory.
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The exception to +BR2_GLOBAL_PATCH_DIR+ being the preferred method for
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specifying custom patches is +BR2_LINUX_KERNEL_PATCH+.
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+BR2_LINUX_KERNEL_PATCH+ should be used to specify kernel patches that
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are available at an URL. *Note:* +BR2_LINUX_KERNEL_PATCHES+ are applied
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after patches available in +BR2_GLOBAL_PATCH_DIR+, as it is done
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from a post-patch hook of the Linux package.
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An example directory structure for where a user has multiple
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directories specified for +BR2_GLOBAL_PATCH_DIR+ may look like this:
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-----
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board/
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+-- common-fooarch
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| +-- patches
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| +-- linux
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| | +-- linux-patch1.patch
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| | +-- linux-patch2.patch
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| +-- u-boot
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| +-- foopkg
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+-- fooarch-board
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+-- patches
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+-- linux
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| +-- linux-patch3.patch
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+-- u-boot
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+-- foopkg
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-----
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If the user has the +BR2_GLOBAL_PATCH_DIR+ configuration option set as
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follows:
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-----
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BR2_GLOBAL_PATCH_DIR="board/common-fooarch board/fooarch-board"
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-----
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Then the patches would applied as follows for the Linux kernel:
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. board/common-fooarch/patches/linux/linux-patch1.patch
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. board/common-fooarch/patches/linux/linux-patch2.patch
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. board/fooarch-board/patches/linux/linux-patch3.patch
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@ -50,10 +50,11 @@ 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 directory containing global package patches. See
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xref:packages-custom[] for details.
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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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@ -64,19 +65,24 @@ How patches are applied
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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 directory or in the
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a package subdirectory named +<packageversion>+, then:
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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 hightly
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recommended to named the patch files like this:
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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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