gluon/docs/dev/build.rst
Sven Roederer 5585f13710 docs/build: add a short summary for some scripts
This summaries giving an overview of a scripts function and a short summary how
it's doing this.
Only the scripts are covered, that are used by the Freifunk-Berlin firmwarebuiler too.
2020-05-31 23:10:26 +02:00

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Build system
============
This page explains internals of the Gluon build system. It is currently very
incomplete; please contribute if you can!
Feed management
---------------
Rather that relying on the *feed.conf* mechanism of OpenWrt directly, Gluon
manages its feeds (*"modules"*) using a collection of scripts. This solution was
selected for multiple reasons:
- Feeds lists from Gluon base and the site repository are combined
- Patchsets are applied to downloaded feed repositories automatically
The following variables specifically affect the feed management:
GLUON_FEEDS
List of base feeds; defined in file *modules* in Gluon base
GLUON_SITE_FEED
List of site feeds; defined in file *modules* in site config
\*_REPO, \*_BRANCH, \*_COMMIT
Git repository URL, branch and and
commit ID of the feeds to use. The branch name may be omitted; the default
branch will be used in this case.
GLUON_BASE_FEEDS
Additional feed definitions to be added to *feeds.conf*
verbatim. By default, this contains a reference to the Gluon base packages;
when using the Gluon build system to build a non-Gluon system, the variable
can be set to the empty string.
Helper scripts
--------------
Several tasks of the build process have been separated from the Makefile into
external scripts, which are stored in the *scripts* directory. This was done to
ease maintenance of these scripts and the Makefile, by avoiding a lot of escaping.
These scripts are either bash or Lua scripts that run on the build system.
default_feeds.sh
Defines the constant ``DEFAULT_FEEDS`` with the names of all feeds listed in
*openwrt/feeds.conf.default*. This script is only used as an include by other
scripts.
feeds.sh
Creates the *openwrt/feeds.conf* file from ``FEEDS`` and ``DEFAULT_FEEDS``. The
feeds from ``FEEDS`` are linked to the matching subfolder of *packages/* and not
explicitly defined feeds of ``DEFAULT_FEEDS`` are setup as dummy (src-dummy).
This *openwrt/feeds.conf* is used to reinstall all packages of all feeds with
the *openwrt/scripts/feeds* tool.
modules.sh
Defines the constant ``GLUON_MODULES`` and ``FEEDS`` by reading the *modules*
file of the root-folder and the site-folder. The returned variables look
like:
- ``FEEDS``: "*feedA feedB ...*"
- ``GLUON_MODULES``: "*openwrt packages/feedA packages/feedB ...*"
This script is only used as an include by other scripts.
patch.sh
(Re-)applies the patches from the *patches* directory to all ``GLUON_MODULES``
and checks out the files to the filesystem.
This is done for each repo by:
- creating a temporary clone of the downloaded repo from the *packages* folder
- use only branch *base*
- applying all patches via *git am* on top of this temporary *base* branch
- name this branch *patched*
- copying the temporary clone to the *packages* folder
- use *git fetch* with the temporary clone as source
- call *git checkout* to update the filesystem
- updating all git submodules
This two directory solution ensures that the current *packages* folder wwill not
be changed until all patches apply. And avoids touching the patched files, when
only the underlying *base* branch is changed, which prevents them from triggering
a recompilation.
update.sh
Sets up a working clone of the ``GLUON_MODULES`` (external repos) from the external
source and installs it into *packages/* directory. It simply tries to set the *base*
branch of the cloned repo to the correct commit. If this fails it fetches the
upstream branch and tries again to set the local *base* branch.