buildroot/docs/manual/customize-patches.adoc
Peter Korsgaard 4984d0f230 utils/add-custom-hashes: add script to manage global patch dir hashes
Add a script to manage the .hash files in the BR2_GLOBAL_PATCH_DIR for
packages using custom versions.

To use it, run in a configured Buildroot directory, E.G.

  make foo_defconfig; ./utils/add-custom-hashes

We support multiple patch directories in BR2_GLOBAL_PATCH_DIR.  If multiple
directories are specified then use the last one as that is likely to be the
most specific one.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
[Peter: silence command -v invocation]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
2023-11-12 11:59:27 +01:00

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// -*- mode:doc -*- ;
// vim: set syntax=asciidoc:
=== Adding project-specific patches and hashes
[[customize-patches]]
==== Providing extra patches
It is sometimes useful to apply 'extra' patches to packages - on top of
those provided in Buildroot. This might be used to support custom
features in a project, for example, or when working on a new
architecture.
The +BR2_GLOBAL_PATCH_DIR+ configuration option can be used to specify
a space separated list of one or more directories containing package
patches.
For a specific version +<packageversion>+ of a specific package
+<packagename>+, patches are applied from +BR2_GLOBAL_PATCH_DIR+ as
follows:
. For every directory - +<global-patch-dir>+ - that exists in
+BR2_GLOBAL_PATCH_DIR+, a +<package-patch-dir>+ will be determined as
follows:
+
* +<global-patch-dir>/<packagename>/<packageversion>/+ if the
directory exists.
+
* Otherwise, +<global-patch-dir>/<packagename>+ if the directory
exists.
. Patches will then be applied from a +<package-patch-dir>+ as
follows:
+
* If a +series+ file exists in the package directory, then patches are
applied according to the +series+ file;
+
* Otherwise, patch files matching +*.patch+ are applied in
alphabetical order. So, to ensure they are applied in the right
order, it is highly recommended to name the patch files like this:
+<number>-<description>.patch+, where +<number>+ refers to the
'apply order'.
For information about how patches are applied for a package, see
xref:patch-apply-order[]
The +BR2_GLOBAL_PATCH_DIR+ option is the preferred method for
specifying a custom patch directory for packages. It can be used to
specify a patch directory for any package in buildroot. It should also
be used in place of the custom patch directory options that are
available for packages such as U-Boot and Barebox. By doing this, it
will allow a user to manage their patches from one top-level
directory.
The exception to +BR2_GLOBAL_PATCH_DIR+ being the preferred method for
specifying custom patches is +BR2_LINUX_KERNEL_PATCH+.
+BR2_LINUX_KERNEL_PATCH+ should be used to specify kernel patches that
are available at a URL. *Note:* +BR2_LINUX_KERNEL_PATCH+ specifies kernel
patches that are applied after patches available in +BR2_GLOBAL_PATCH_DIR+,
as it is done from a post-patch hook of the Linux package.
[[customize-hashes]]
==== Providing extra hashes
Buildroot bundles a xref:adding-packages-hash[list of hashes] against
which it checks the integrity of the downloaded archives, or of those
it generates locally from VCS checkouts. However, it can only do so
for the known versions; for packages where it is possible to specify
a custom version (e.g. a custom version string, a remote tarball URL,
or a VCS repository location and changeset), Buildroot can't carry
hashes for those.
For users concerned with the integrity of such downloads, it is possible
to provide a list of hashes that Buildroot can use to check arbitrary
downloaded files. Those extra hashes are looked up similarly to the
extra patches (above); for each directory in +BR2_GLOBAL_PATCH_DIR+,
the first file to exist is used to check a package download:
* +<global-patch-dir>/<packagename>/<packageversion>/<packagename>.hash+
* +<global-patch-dir>/<packagename>/<packagename>.hash+
The +utils/add-custom-hashes+ script can be used to generate these files.