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7e5b637483
Update the expo documentation to include mention of this new object type. Signed-off-by: Simon Glass <sjg@chromium.org>
170 lines
5.6 KiB
ReStructuredText
170 lines
5.6 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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Configuration Editor
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====================
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Introduction
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------------
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U-Boot provides a configuration editor which allows settings to be changed in
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a GUI or text environment.
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This feature is still in development and has a number of limitations. For
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example, cedit only supports menu items (there is no numeric or text entry),
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provides no support for colour text and does not support scrolling. Still it is
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possible to use it for simple applications.
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Overview
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--------
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The configuration editor makes use of :doc:`expo` to build a description of the
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configuration screens and allow user to interact with it.
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To create a single-scene cedit for your application:
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#. Design the scene, i.e. the objects that need to be present and what their
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possible values are
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#. Enter this in .dts format
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#. Create a header file containing the IDs
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#. Run the 'expo.py' tool to generate a .dtb file containing the layout, which
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can be used by U-Boot
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#. Use the :doc:`../usage/cmd/cedit` to create the cedit, read the settings,
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present the cedit to the user and save the settings afterwards.
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Each of these is described in a separate section. See :ref:`expo_example` for
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an example file.
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Design a scene
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--------------
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Using a piece of paper or a drawing tool, lay out the objects you want in your
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scene. Typically you will use the default layout engine, which simply puts items
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one after the other from top to bottom. So use a single column and show the
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prompt and value for each object.
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For menu items, show one of the values, but keep in mind what else you need.
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Create an expo-format file
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--------------------------
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The description is in the form of a devicetree file, as documented at
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:ref:`expo_format`. Since everything in an expo has an ID number (an integer
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greater than 1) the description is written terms of these IDs. They each have
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an enum value. which is typically taken care of by the `expo.py` tool.
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The expo should have a `scenes` node with a named scene as a subnode. Within the
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scene, add properties for the scene, then a subnode for each object in the
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scene.
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All object nodes require an `id` value and a `type` property. Other properties
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depend on the type. For example, a menu has a `title` and an `item-label` list
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proving the text for the menu items, as well as an `item-id` list providing the
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ID of each menu item, so it can be selected.
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Text properties may have two variants. For example `title` specifies the title
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of a menu, but you can instead use `title-id` to specify the string ID to use as
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the title. String are defined in a separate area, common to the whole expo,
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which contains a subnode for each string. Within that subnode are the ID and the
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`value` (i.e. the text). For now only English is supported, but in future it may
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be possible to append a language identifier to provide other values (e.g.
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'value-es' for Spanish).
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Create an ID header-file
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------------------------
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Expo needs to know the integer value to use for every ID referenced in your
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expo-format file. For example, if you have defined a `cpu-speed` node with an
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id of `ID_CPU_SPEED`, then Expo needs to know the value of `ID_CPU_SPEED`.
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When you write C code to use the expo, you may need to know the IDs. For
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example, to find which value the user selected in `cpu-speed` menu, you must
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use the `ID_CPU_SPEED` ID. The ID is the only way to refer to anything in Expo.
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Since we need a shared set of IDs, it is best to have a header file containing
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them. Expo supports doing this with an enum, where every ID is listed in the
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enum::
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enum {
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ZERO,
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ID_PROMPT,
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ID_SCENE1,
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ID_SCENE1_TITLE,
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...
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};
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The C compiler can parse this directly. The `expo.py` tool parses it for expo.
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Create a header file containing every ID mentioned in your expo. Try to group
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related things together.
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Build the expo layout
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---------------------
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Use the `expo.py` tool to build a .dtb for your expo::
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./tools/expo.py -e expo_ids.h -l expo_layout.dts -o expo.dtb
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This uses the enum in the provided header file to get the ID numbers, grabs
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the `.dts` file, inserts the ID numbers and then uses the devicetree compiler to
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build a `.dtb` file.
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If you get an error::
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Devicetree compiler error:
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Error: <stdin>:9.19-20 syntax error
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FATAL ERROR: Unable to parse input tree
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that means that something is wrong with your syntax, or perhaps you have an ID
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in the `.dts` file that is not mentioned in your enum. Check both files and try
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again.
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Use the command interface
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-------------------------
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See the :doc:`../usage/cmd/cedit` command for information on available commands.
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Typically you will use `cedit load` to load the `.dtb` file and `cedit run` to
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let the user interact with it.
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Multiple scenes
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---------------
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Expo supports multiple scenes but has no pre-determined way of moving between
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them. You could use selection of a menu item as a signal to change the scene,
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but this is not currently implemented in the cedit code (see `cedit_run()`).
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Themes
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------
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The configuration editor uses simple expo themes. The theme is read from
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`/bootstd/cedit-theme` in the devicetree.
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Reading and writing settings
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----------------------------
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Cedit provides several options for persistent settings:
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- Writing an FDT file to a filesystem
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- Writing to U-Boot's environment variables, which are then typically stored in
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a persistent manner
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- Writing to CMOS RAM registers (common on x86 machines). Note that textline
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objects do not appear in CMOS RAM registers
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For now, reading and writing settings is not automatic. See the
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:doc:`../usage/cmd/cedit` for how to do this on the command line or in a
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script.
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