Configuration Editor


U-Boot provides a configuration editor which allows settings to be changed in a GUI or text environment.

This feature is still in development and has a number of limitations. For example, cedit only supports menu items (there is no numeric or text entry), provides no support for colour text and does not support scrolling. Still it is possible to use it for simple applications.


The configuration editor makes use of Expo menu to build a description of the configuration screens and allow user to interact with it.

To create a single-scene cedit for your application:

  1. Design the scene, i.e. the objects that need to be present and what their possible values are

  2. Enter this in .dts format

  3. Create a header file containing the IDs

  4. Run the ‘’ tool to generate a .dtb file containing the layout, which can be used by U-Boot

  5. Use the cedit command to create the cedit, read the settings, present the cedit to the user and save the settings afterwards.

Each of these is described in a separate section. See Expo format example for an example file.

Design a scene

Using a piece of paper or a drawing tool, lay out the objects you want in your scene. Typically you will use the default layout engine, which simply puts items one after the other from top to bottom. So use a single column and show the prompt and value for each object.

For menu items, show one of the values, but keep in mind what else you need.

Create an expo-format file

The description is in the form of a devicetree file, as documented at Expo Format. Since everything in an expo has an ID number (an integer greater than 1) the description is written terms of these IDs. They each have an enum value. which is typically taken care of by the tool.

The expo should have a scenes node with a named scene as a subnode. Within the scene, add properties for the scene, then a subnode for each object in the scene.

All object nodes require an id value and a type property. Other properties depend on the type. For example, a menu has a title and an item-label list proving the text for the menu items, as well as an item-id list providing the ID of each menu item, so it can be selected.

Text properties may have two variants. For example title specifies the title of a menu, but you can instead use title-id to specify the string ID to use as the title. String are defined in a separate area, common to the whole expo, which contains a subnode for each string. Within that subnode are the ID and the value (i.e. the text). For now only English is supported, but in future it may be possible to append a language identifier to provide other values (e.g. ‘value-es’ for Spanish).

Create an ID header-file

Expo needs to know the integer value to use for every ID referenced in your expo-format file. For example, if you have defined a cpu-speed node with an id of ID_CPU_SPEED, then Expo needs to know the value of ID_CPU_SPEED.

When you write C code to use the expo, you may need to know the IDs. For example, to find which value the user selected in cpu-speed menu, you must use the ID_CPU_SPEED ID. The ID is the only way to refer to anything in Expo.

Since we need a shared set of IDs, it is best to have a header file containing them. Expo supports doing this with an enum, where every ID is listed in the enum:

enum {



The C compiler can parse this directly. The tool parses it for expo.

Create a header file containing every ID mentioned in your expo. Try to group related things together.

Build the expo layout

Use the tool to build a .dtb for your expo:

./tools/ -e expo_ids.h -l expo_layout.dts -o expo.dtb

This uses the enum in the provided header file to get the ID numbers, grabs the .dts file, inserts the ID numbers and then uses the devicetree compiler to build a .dtb file.

If you get an error:

Devicetree compiler error:
Error: <stdin>:9.19-20 syntax error
FATAL ERROR: Unable to parse input tree

that means that something is wrong with your syntax, or perhaps you have an ID in the .dts file that is not mentioned in your enum. Check both files and try again.

Use the command interface

See the cedit command command for information on available commands. Typically you will use cedit load to load the .dtb file and cedit run to let the user interact with it.

Multiple scenes

Expo supports multiple scenes but has no pre-determined way of moving between them. You could use selection of a menu item as a signal to change the scene, but this is not currently implemented in the cedit code (see cedit_run()).


The configuration editor uses simple expo themes. The theme is read from /bootstd/cedit-theme in the devicetree.

Reading and writing settings

Cedit provides several options for persistent settings:

  • Writing an FDT file to a filesystem

  • Writing to U-Boot’s environment variables, which are then typically stored in a persistent manner

  • Writing to CMOS RAM registers (common on x86 machines). Note that textline objects do not appear in CMOS RAM registers

For now, reading and writing settings is not automatic. See the cedit command for how to do this on the command line or in a script.