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authorTom Zanussi <tom.zanussi@linux.intel.com>2014-07-07 16:05:44 -0500
committerRichard Purdie <richard.purdie@linuxfoundation.org>2014-07-10 17:37:40 +0100
commita3dbe46dd28a6fd9e6c21f6bbb6a12578df9dff3 (patch)
treeb1bb8cd732092afa77c4573da3cfe8703bbaab77
parentd03f39a99058c2393d7b50ac4909bdaa84b09920 (diff)
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wic: Add general 'plugins' help topic
Add a category for help topics with an initial help topic discussing source plugins. Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Saul Wold <sgw@linux.intel.com>
-rw-r--r--scripts/lib/image/help.py101
-rwxr-xr-xscripts/wic15
2 files changed, 109 insertions, 7 deletions
diff --git a/scripts/lib/image/help.py b/scripts/lib/image/help.py
index 6de7ab023e0..a4f27ab68e7 100644
--- a/scripts/lib/image/help.py
+++ b/scripts/lib/image/help.py
@@ -87,7 +87,11 @@ wic_usage = """
create Create a new OpenEmbedded image
list List available values for options and image properties
- See 'wic help COMMAND' for more information on a specific command.
+ Help topics:
+ plugins wic plugins - Overview and API
+
+ See 'wic help <COMMAND or HELP TOPIC>' for more information on a specific
+ command or help topic.
"""
wic_help_usage = """
@@ -323,3 +327,98 @@ DESCRIPTION
["offset", "offset of the partition within the image"]
"""
+
+wic_plugins_help = """
+
+NAME
+ wic plugins - Overview and API
+
+DESCRIPTION
+ plugins allow wic functionality to be extended and specialized by
+ users. This section documents the plugin interface, which is
+ currently restricted to 'source' plugins.
+
+ 'Source' plugins provide a mechanism to customize various aspects
+ of the image generation process in wic, mainly the contents of
+ partitions.
+
+ Source plugins provide a mechanism for mapping values specified in
+ .wks files using the --source keyword to a particular plugin
+ implementation that populates a corresponding partition.
+
+ A source plugin is created as a subclass of SourcePlugin (see
+ scripts/lib/mic/pluginbase.py) and the plugin file containing it
+ is added to scripts/lib/mic/plugins/source/ to make the plugin
+ implementation available to the wic implementation.
+
+ Source plugins can also be implemented and added by external
+ layers - any plugins found in a scripts/lib/mic/plugins/source/
+ directory in an external layer will also be made available.
+
+ 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 bootimg-pcbios .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.
+
+ The SourcePlugin class defines the following methods, which is the
+ current set of methods that can be implemented/overridden by
+ --source plugins. Any methods not implemented by a SourcePlugin
+ subclass inherit the implementations present in the SourcePlugin
+ class (see the SourcePlugin source for details):
+
+ do_prepare_partition()
+ Called to do the actual content population for a partition
+ i.e. it 'prepares' the final partition image which will be
+ incorporated into the disk image.
+
+ do_configure_partition()
+ Called before do_prepare_partition(), typically used to
+ create custom configuration files for a partition, for
+ example syslinux or grub config files.
+
+ do_install_disk()
+ Called after all partitions have been prepared and assembled
+ into a disk image. This provides a hook to allow
+ finalization of a disk image e.g. to write an MBR to it.
+
+ do_stage_partition()
+ Special content staging hook called before
+ do_prepare_partition(), normally empty.
+
+ Typically, a partition will just use the passed-in parame
+ e.g straight bootimg_dir, etc, but in some cases, things
+ need to be more tailored e.g. to use a deploy dir + /boot,
+ etc. This hook allows those files to be staged in a
+ customized fashion. Not that get_bitbake_var() allows you
+ to acces non-standard variables that you might want to use
+ for this.
+
+ 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 method names of interest - on success, these will be filled in
+ with the actual methods. Please see the implementation for
+ examples and details.
+"""
diff --git a/scripts/wic b/scripts/wic
index 00eddfd7bca..ac3ed160d9b 100755
--- a/scripts/wic
+++ b/scripts/wic
@@ -240,12 +240,15 @@ wic_help_topic_usage = """
"""
subcommands = {
- "create": [wic_create_subcommand,
- wic_create_usage,
- wic_create_help],
- "list": [wic_list_subcommand,
- wic_list_usage,
- wic_list_help],
+ "create": [wic_create_subcommand,
+ wic_create_usage,
+ wic_create_help],
+ "list": [wic_list_subcommand,
+ wic_list_usage,
+ wic_list_help],
+ "plugins": [wic_help_topic_subcommand,
+ wic_help_topic_usage,
+ wic_plugins_help],
}