73ce09065f
Define the SourcePlugin class, which is the class that should be
subclassed to create a 'source' plugin.
'Source' plugins provide a mechanism to customize various aspects of
the image generation process in wic, mainly the contents of
partitions.
The initial version of wic defined a --source param for partitions,
which was in the first revision hard-coded to two possible values:
rootfs and bootimg.
This patch essentially removes the hard-coded --bootimg param and
replaces it with a plugin system that maps the value specified as
--source to a particular 'source' plugin instead.
A 'source' plugin is created as a subclass of SourcePlugin and the
plugin file containing it is added to scriptsl/lib/mic/plugins/source/
to make the plugin implementation available to the wic implementation.
When the wic implementation needs to invoke a partition-specific
implementation, it looks for the plugin that has the same name as the
--source param given to that partition. For example, if the partition
is set up like this:
part /boot --source bootimg-pcbios ...
then the methods defined as class members of the plugin having the
matching .name class member would be used.
To be more concrete, here's the plugin definition that would match a
'--source bootimg-pcbios' usage, along with an example method that
would be called by the wic implementation when it needed to invoke an
implementation-specific partition-preparation function:
class BootimgPcbiosPlugin(SourcePlugin):
name = 'bootimg-pcbios'
@classmethod
def do_prepare_partition(self, part, ...)
If the subclass itself doesn't implement a function, a 'default'
version in a superclass will be located and used, which is why all
plugins must be derived from SourcePlugin.
This scheme is extensible - adding more hooks is a simple matter of
adding more plugin methods to SourcePlugin and derived classes. The
code that then needs to call the plugin methods the uses
plugin.get_source_plugin_methods() to find the method(s) needed by the
call; this is done by filling up a dict with keys containing the
methon names of interest - on success, these will be filled in with
the actual methods. fPlease see the implementation for examples and
details.
Note that a source plugin need not restrict itself to methods that
apply directly to partitions - methods can also be defined for higher
level processing such as at the 'disk' level. The
get_default_source_plugin() of DirectImageCreator allows the default
source plugin to be retrieved; by default this is set to be the same
plugin used for the /boot partition, but that can be overridden by
specifying a different --source and therefore different plugin on the
'bootloader' line. This isn't ideal, but it avoids forcing a new
high-level object to be defined for that purpose.
Note that the '--source rootfs' param remains as its current
hard-coded value, which is just the rootfs to be used to populate the
partition - by default, that's just the value of the bitbake
ROOTFS_DIR variable (or whatever was passed in using the -r param).
Note that this also could also be overridden by creating a source
plugin using a different name; at this point, unlike with bootimg,
there's been no need to do so.
(From OE-Core rev: 663833d8ecccb36ab42150bc5c9c00be79fa5b93)
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Poky
Poky is an integration of various components to form a complete prepackaged build system and development environment. It features support for building customised embedded device style images. There are reference demo images featuring a X11/Matchbox/GTK themed UI called Sato. The system supports cross-architecture application development using QEMU emulation and a standalone toolchain and SDK with IDE integration.
Additional information on the specifics of hardware that Poky supports is available in README.hardware. Further hardware support can easily be added in the form of layers which extend the systems capabilities in a modular way.
As an integration layer Poky consists of several upstream projects such as BitBake, OpenEmbedded-Core, Yocto documentation and various sources of information e.g. for the hardware support. Poky is in turn a component of the Yocto Project.
The Yocto Project has extensive documentation about the system including a reference manual which can be found at: http://yoctoproject.org/documentation
OpenEmbedded-Core is a layer containing the core metadata for current versions of OpenEmbedded. It is distro-less (can build a functional image with DISTRO = "nodistro") and contains only emulated machine support.
For information about OpenEmbedded, see the OpenEmbedded website: http://www.openembedded.org/
Where to Send Patches
As Poky is an integration repository, patches against the various components should be sent to their respective upstreams.
bitbake: bitbake-devel@lists.openembedded.org
meta-yocto: poky@yoctoproject.org
Most everything else should be sent to the OpenEmbedded Core mailing list. If in doubt, check the oe-core git repository for the content you intend to modify. Before sending, be sure the patches apply cleanly to the current oe-core git repository. openembedded-core@lists.openembedded.org
Note: The scripts directory should be treated with extra care as it is a mix of oe-core and poky-specific files.