Package Structure

The files in an installed eCos source tree are organized in a natural tree structure, grouping together files which work together into Packages. For example, the kernel files are all together in:

BASE_DIR/kernel/<version>/include/
BASE_DIR/kernel/<version>/src/
BASE_DIR/kernel/<version>/tests/

and µITRON compatibility layer files are in:

BASE_DIR/compat/uitron/<version>/include/
BASE_DIR/compat/uitron/<version>/src/
BASE_DIR/compat/uitron/<version>/tests/

The feature of these names which is of interest here is the <version> near the end. It may seem odd to place a version number deep in the path, rather than having something like BASE_DIR/<version>/...everything... or leaving it up to you to choose a different install-place when a new release of the system arrives.

The rationale for this organization is historic as in practice developers maintain their source code under revision control systems such as Mercurial, GIT or SourceSafe using the version directory current in place of <version> throughout. The version directory current is favored by most developers.

The <version> schema is still maintained as it does permit developers to easily switch between different versions of specific packages within their configuration without having to manipulate their revision control system or partion packages into their own revision control system. It also permits develops to upgrade only specific packages to newer versions while retaining the remainder on earlier versions that have been previously qualified by a standards or certification agency.

Integration with Revision Control Systems

Many developers have their own source code control system, version control system or equivalent, and will want to use it with eCos and eCosPro sources. Since new releases of eCos and eCosPro come with different pathnames for all the source files, a little work is necessary to import a new release into your source repository.

For example, eCosCentric maintains eCosPro within Mercurial, a distributed source revision control system, using a number of source repositories with all package versions as current. An eCosPro release is constructed by merging all repositories into a new single release directory and renaming all current directories to <version>, as well as setting the <version> of all templates.

An eCosPro release may therefore be returned into a source revision control system by renaming all <version> directories below packages back to current and committing the resulting directory structure into the repository.

“current” is recommended because ecosconfig recognizes it and places it first in any list of versions.

For example, within a POSIX shell environment such as bash (normally available under Linux and provided with the eCosPro host tools for Windows hosts) use the following command:

find . -name <version> -type d -printf 'mv %p %h/current\n' | bash

Having carried out such a renaming operation, your source tree will now look like this:

BASE_DIR/kernel/current/include/
BASE_DIR/kernel/current/src/
BASE_DIR/kernel/current/tests/
  ...
BASE_DIR/compat/uitron/current/include/
BASE_DIR/compat/uitron/current/src/
BASE_DIR/compat/uitron/current/tests/

which is a suitable format for import into your own source code control system. When you get a subsequent release of eCosPro, do the same thing and use your own source code control system to manage the new source base, by importing the new version from

NEW_BASE_DIR/kernel/current/include/

and so on.

The eCos build tool will now offer only the “current” version of each package; select this for the packages you wish to use.

Alternatively you may choose to create two versions of each package with each <version> directory lying alongside the next and current containing the most recent <version>. For example:

cd $ECOS_REPOSITORY
find . -name <version> -type d -printf 'cp -r %p %h/current\n' | bash

Having carried out such a copy operation, your source tree will now look like this:

BASE_DIR/kernel/current/include/
BASE_DIR/kernel/<version>/include/
BASE_DIR/kernel/current/src/
BASE_DIR/kernel/<version>/src/
BASE_DIR/kernel/current/tests/
BASE_DIR/kernel/<version>/tests/
  ...
BASE_DIR/compat/uitron/current/include/
BASE_DIR/compat/uitron/<version>/include/
BASE_DIR/compat/uitron/current/src/
BASE_DIR/compat/uitron/<version>/src/
BASE_DIR/compat/uitron/current/tests/
BASE_DIR/compat/uitron/<version>/tests/

In simple terms, while you initially may have two identical version directories, when you overlay a new version on top of an existing directory tree, the older files within current will be replaced by the newer <version>. Within your configuration, however, all packages marked to use the older version will remain fixed while those marked to use current will switch to a newer version.

The above simple method, however, is strongly discouraged. Care must be taken when merging two packages directories from different release repositories. For example, the file ecos.db is not versioned and is common to both releases' packages directories. Changes to made to this file will be lost. In addition, the target definition within ecos.db for a newer release may contain additional packages, such a new device driver which was not present in the older version of ecos.db. Developers are therefore advised to use the merge command of the ecosadmin.tcl tool which will merge the two versions of ecos.db in addition to overlaying new <version> subdirectories into the target repository. In addition, while merge will copy over the newer <version> subdirectories it will not replace the contents of pre-existing subdirectories such as current. This may, however, be made an option in a newer release of the ecosadmin.tcl tool and currently can be overcome through the following commands:

cd NEW_REPOSITORY
find . -name <version> -type d -printf 'cp -rf %p/. $ECOS_REPOSITORY/%h/current\n' | bash

Note: For the example given, the updated target definition in the merged repository will require use of the new device driver not present in the older release as a result of the updated target definition within ecos.db.

Warning

Making such a change has implications for any build trees you already have in use. A configured build tree contains information about the selected packages and their selected versions. Changing the name of the “versioning” folder in the source tree invalidates this information, and in consequence it also invalidates any local configuration options you have set up in this build tree. So if you want to change the version information in the source tree, do it first, before investing any serious time in configuring and building your system. When you create a new build tree to deal with the new source layout, it will contain default settings for all the configuration options, just like the old build tree did before you configured it. You will need to redo that configuration work in the new tree.

Moving source code around also invalidates debugging information in any programs or libraries built from the old tree; these will need to be rebuilt.

2017-02-09
Documentation license for this page: Open Publication License