Energy Manager OS (EMOS) & EM SDK build scripts
===============================================

The configuration files and scripts in this repository are used to set up the
Yocto-based build environment for the EM SDK, while also allowing to add custom
layers to the bulid configuration.

Two scripts are provided:

* em-update:

  Clones or updates the git repositories for the used Yocto layers in the
  "layers" subdirectory, as configured in em-layers.conf

* em-build-env:

  em-build-env must be sourced by the shell, e.g.:

    . ./em-build-env

  This script corresponds to oe-init-build-env found in OpenEmbedded/Yocto, but
  it will additionally update the conf/bblayers file. It must be sourced in each
  shell that is used to run builds. After sourcing em-build-env, the command

    bitbake em-bundle-sdk

  is used to build the default EM update bundle. The Yocto build configuration
  can be adjusted in conf/local.conf in the generated build directory or in
  custom layers.


Configuration
-------------

The cloned layers are configured in the files em-layers.conf and
local/em-layers.conf. local/em-layers.conf does not exist by default and can be
used to add custom layers to the build. The "local" directory is excluded from
source control in the em-build repo itself; if desired, "local" can be made into
a separate git repository to track changes of local/em-layers.conf.

An example local/em-layers.conf is given in the following:

    LAYERS += meta-custom

    meta-custom_repo           = ssh://git@git.example.com/meta-custom.git
    meta-custom_branch         = master
    # meta-custom_commit       =
    # meta-custom_subdirs      =

Each layer must be a git repository; the URL and branch that should be cloned
are configured in the ..._repo and ..._branch variables.

The ..._commit variable defines a specific commit from the cloned branch that
should be checked out to allow creating a reproducible build environment. If
unset, the layer will be updated to the HEAD of the given branch on each run of
em-update.

The ..._subdirs variable allows to provide a (space-separated) list of
subdirectories of the git repository that should be added to bblayers.conf. If
unset, the toplevel directory of the repository will be used.

For development purposes, it is also possible to add manually managed layer
directories under layers/. By adding such a layer to local/em-layers.conf, but
leaving the ..._repo variable unset, em-update will simply ignore the directory.
em-build-env will add it (or the configured subdirs) to bblayers.conf.

The em-layers.conf files follow standard Makefile syntax.