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>Package Organization</TITLE
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>The <SPAN
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>eCos</SPAN
> Component Writer's Guide</TH
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><DIV
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><H1
><A
NAME="PACKAGE">Chapter 2. Package Organization</H1
><DIV
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><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="package.html#PACKAGE.HIERARCHY"
>Packages and the Component Repository</A
></DT
><DT
><A
HREF="package.versions.html"
>Package Versioning</A
></DT
><DT
><A
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>Package Contents and Layout</A
></DT
><DT
><A
HREF="package.distrib.html"
>Making a Package Distribution</A
></DT
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><P
>For a package to be usable in the <SPAN
CLASS="APPLICATION"
>eCos</SPAN
> component framework it must
conform to certain rules imposed by that framework. Packages must be
distributed in a form that is understood by the component repository
administration tool. There must be a top-level <SPAN
CLASS="APPLICATION"
>CDL</SPAN
> script which
describes the package to the component framework. There are certain
limitations related to how a package gets built, so that the package
can still be used in a variety of host environments. In addition to
these rules, the component framework provides a number of guidelines.
Packages do not have to conform to the guidelines, but sticking to
them can simplify certain operations.</P
><P
>This chapter deals with the general organization of a package, for
example how to distinguish between private and exported header files.
<A
HREF="language.html"
>Chapter 3</A
> describes the <SPAN
CLASS="APPLICATION"
>CDL</SPAN
> language.
<A
HREF="build.html"
>Chapter 4</A
> details the build process.</P
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="PACKAGE.HIERARCHY">Packages and the Component Repository</H1
><P
>All <SPAN
CLASS="APPLICATION"
>eCos</SPAN
> installations include a component repository. This is a
directory structure for all installed packages. The component
framework comes with an administration tool that allows new packages
or new versions of a package to be installed, old packages to be
removed, and so on. The component repository includes a simple
database, maintained by the administration tool, which contains
details of the various packages.</P
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><P
>Each package has its own little directory hierarchy within the
component repository. Keeping several packages in a single directory
is illegal. The error, infra and kernel packages all live at the
top-level of the repository. For other types of packages there are
some pre-defined directories: <TT
CLASS="FILENAME"
>compat</TT
> is used for compatibility
packages, which implement other interfaces such as µITRON or POSIX
using native <SPAN
CLASS="APPLICATION"
>eCos</SPAN
> calls; <TT
CLASS="FILENAME"
>hal</TT
>
is used for packages that port <SPAN
CLASS="APPLICATION"
>eCos</SPAN
> to different architectures or
platforms, and this directory is further organized on a
per-architecture basis; <TT
CLASS="FILENAME"
>io</TT
> is
intended for device drivers; <TT
CLASS="FILENAME"
>language</TT
> is used for language support
libraries, for example the C library. There are no strict rules
defining where new packages should get installed. Obviously if an
existing top-level directory such as <TT
CLASS="FILENAME"
>compat</TT
> is applicable then the new package
should go in there. If a new category is desirable then it is possible
to create a new sub-directory in the component repository. For
example, an organization planning to release a number of <SPAN
CLASS="APPLICATION"
>eCos</SPAN
>
packages may want them all to appear below a sub-directory
corresponding to the organization's name — in the hope that
the name will not change too often. It is possible to add new packages
directly to the top-level of the component repository, but this should
be avoided.</P
><P
>The <SPAN
CLASS="DATABASE"
>ecos.db</SPAN
> file holds the component repository
database and is managed by the administration tool. The various
configuration tools read in this file when they start-up to obtain
information about the various packages that have been installed. When
developing a new package it is necessary to add some information to
the file, as described in <A
HREF="language.database.html"
>the Section called <I
>Updating the <SPAN
CLASS="DATABASE"
>ecos.db</SPAN
> database</I
> in Chapter 3</A
>. The
<TT
CLASS="FILENAME"
>templates</TT
> directory holds
various configuration templates.</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>Earlier releases of <SPAN
CLASS="APPLICATION"
>eCos</SPAN
> came with two separate files,
<TT
CLASS="FILENAME"
>targets</TT
> and <TT
CLASS="FILENAME"
>packages</TT
>. The
<SPAN
CLASS="DATABASE"
>ecos.db</SPAN
> database replaces both of these.</P
></BLOCKQUOTE
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><P
></P
><TABLE
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><TD
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><B
>Caution</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>The current <SPAN
CLASS="DATABASE"
>ecos.db</SPAN
> database does not yet provide
all of the information needed by the component framework. Its format
is subject to change in future releases, and the file may be replaced
completely if necessary. There are a number of other likely future
developments related to the component repository and the database. The
way targets are described is subject to change. Sometimes it is
desirable for component writers to do their initial development in a
directory outside the component repository, but there is no specific
support in the framework for that yet.</P
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