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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >cdl_component</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="The eCos Component Writer's Guide" HREF="cdl-guide.html"><LINK REL="UP" TITLE="CDL Language Specification" HREF="reference.html"><LINK REL="PREVIOUS" TITLE="cdl_option" HREF="ref.cdl-option.html"><LINK REL="NEXT" TITLE="cdl_package" HREF="ref.cdl-package.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >The <SPAN CLASS="APPLICATION" >eCos</SPAN > Component Writer's Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="ref.cdl-option.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="ref.cdl-package.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="REF.CDL-COMPONENT"><TT CLASS="LITERAL" >cdl_component</TT ></H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN3091" ></A ><H2 >Name</H2 >Command <TT CLASS="LITERAL" >cdl_component</TT > -- Define a component, a collection of configuration options</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN3095"><H2 >Synopsis</H2 ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="SYNOPSIS" >cdl_component <name> { … }</PRE ></TD ></TR ></TABLE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN3097" ></A ><H2 >Description</H2 ><P >A component is a configuration option that can contain additional options and sub-components. The body of a <TT CLASS="LITERAL" >cdl_component</TT > can contain the same properties as that of a <TT CLASS="LITERAL" >cdl_option</TT >. There is an additional property, <SPAN CLASS="PROPERTY" >script</SPAN > which allows configuration data to be split into multiple files. It is also possible for a component body to include <TT CLASS="LITERAL" >cdl_component</TT >, <TT CLASS="LITERAL" >cdl_option</TT > and <TT CLASS="LITERAL" >cdl_interface</TT > entities that should go below this component in the configuration hierarchy.</P ><P ><TT CLASS="LITERAL" >cdl_component</TT > is implemented as a Tcl command that takes two arguments, a name and a body. The name must be a valid C preprocessor identifier: a sequence of upper or lower case letters, digits or underscores, starting with a non-digit character; identifiers beginning with an underscore should normally be avoided because they may clash with system packages or with identifiers reserved for use by the compiler. Within a single configuration, names must be unique. If a configuration contained two packages which defined the same entity <TT CLASS="LITERAL" >CYGIMP_SOME_OPTION</TT >, any references to that entity in a <SPAN CLASS="PROPERTY" >requires</SPAN > property or any other expression would be ambiguous. It is possible for a given name to be used by two different packages if those packages should never be loaded into a single configuration. For example, architectural HAL packages are allowed to re-use certain names because a single configuration cannot target two different architectures. For a recommended naming convention see <A HREF="package.contents.html" >the Section called <I >Package Contents and Layout</I > in Chapter 2</A >.</P ><P >The second argument to <TT CLASS="LITERAL" >cdl_component</TT > is a body of properties and other commands, typically surrounded by braces so that the Tcl interpreter treats it as a single argument. This body will be processed by a recursive invocation of the Tcl interpreter, extended with additional commands for the various properties that are allowed inside a <TT CLASS="LITERAL" >cdl_component</TT >. The valid commands are:</P ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><A HREF="ref.active-if.html" ><SPAN CLASS="PROPERTY" >active_if</SPAN ></A ></DT ><DD ><P >Allow additional control over the active state of this component.</P ></DD ><DT ><A HREF="ref.calculated.html" ><SPAN CLASS="PROPERTY" >calculated</SPAN ></A ></DT ><DD ><P >The component's value is not directly user-modifiable, it is calculated using a suitable CDL expression.</P ></DD ><DT ><A HREF="ref.cdl-component.html" ><TT CLASS="LITERAL" >cdl_component</TT ></A ></DT ><DD ><P >Define a sub-component.</P ></DD ><DT ><A HREF="ref.cdl-interface.html" ><TT CLASS="LITERAL" >cdl_interface</TT ></A ></DT ><DD ><P >Define an interface which should appear immediately below this component in the configuration hierarchy.</P ></DD ><DT ><A HREF="ref.cdl-option.html" ><TT CLASS="LITERAL" >cdl_option</TT ></A ></DT ><DD ><P >Define a configuration option which should appear immediately below this component in the configuration hierarchy.</P ></DD ><DT ><A HREF="ref.compile.html" ><SPAN CLASS="PROPERTY" >compile</SPAN ></A ></DT ><DD ><P >List the source files that should be built if this component is active and enabled.</P ></DD ><DT ><A HREF="ref.default-value.html" ><SPAN CLASS="PROPERTY" >default_value</SPAN ></A ></DT ><DD ><P >Provide a default value for this component using a CDL expression.</P ></DD ><DT ><A HREF="ref.define.html" ><SPAN CLASS="PROPERTY" >define</SPAN ></A ></DT ><DD ><P >Specify additional <TT CLASS="LITERAL" >#define</TT > symbols that should go into the owning package's configuration header file.</P ></DD ><DT ><A HREF="ref.define-format.html" ><SPAN CLASS="PROPERTY" >define_format</SPAN ></A ></DT ><DD ><P >Control how the component's value will appear in the configuration header file.</P ></DD ><DT ><A HREF="ref.define-proc.html" ><SPAN CLASS="PROPERTY" >define_proc</SPAN ></A ></DT ><DD ><P >Use a fragment of Tcl code to output additional data to configuration header files.</P ></DD ><DT ><A HREF="ref.description.html" ><SPAN CLASS="PROPERTY" >description</SPAN ></A ></DT ><DD ><P >Provide a textual description for this component.</P ></DD ><DT ><A HREF="ref.display.html" ><SPAN CLASS="PROPERTY" >display</SPAN ></A ></DT ><DD ><P >Provide a short string describing this component.</P ></DD ><DT ><A HREF="ref.doc.html" ><SPAN CLASS="PROPERTY" >doc</SPAN ></A ></DT ><DD ><P >The location of on-line documentation for this component.</P ></DD ><DT ><A HREF="ref.flavor.html" ><SPAN CLASS="PROPERTY" >flavor</SPAN ></A ></DT ><DD ><P >Specify the nature of this component.</P ></DD ><DT ><A HREF="ref.if-define.html" ><SPAN CLASS="PROPERTY" >if_define</SPAN ></A ></DT ><DD ><P >Output a common preprocessor construct to a configuration header file. </P ></DD ><DT ><A HREF="ref.implements.html" ><SPAN CLASS="PROPERTY" >implements</SPAN ></A ></DT ><DD ><P >Enabling this component provides one instance of a more general interface. </P ></DD ><DT ><A HREF="ref.legal-values.html" ><SPAN CLASS="PROPERTY" >legal_values</SPAN ></A ></DT ><DD ><P >Impose constraints on the possible values for this component.</P ></DD ><DT ><A HREF="ref.make.html" ><SPAN CLASS="PROPERTY" >make</SPAN ></A ></DT ><DD ><P >An additional custom build step associated with this component, resulting in a target that should not go directly into a library.</P ></DD ><DT ><A HREF="ref.make-object.html" ><SPAN CLASS="PROPERTY" >make_object</SPAN ></A ></DT ><DD ><P >An additional custom build step associated with this component, resulting in an object file that should go into a library.</P ></DD ><DT ><A HREF="ref.no-define.html" ><SPAN CLASS="PROPERTY" >no_define</SPAN ></A ></DT ><DD ><P >Suppress the normal generation of a preprocessor <TT CLASS="LITERAL" >#define</TT > symbol in a configuration header file.</P ></DD ><DT ><A HREF="ref.parent.html" ><SPAN CLASS="PROPERTY" >parent</SPAN ></A ></DT ><DD ><P >Control the location of this component in the configuration hierarchy. </P ></DD ><DT ><A HREF="ref.requires.html" ><SPAN CLASS="PROPERTY" >requires</SPAN ></A ></DT ><DD ><P >List constraints that the configuration should satisfy if this component is active and enabled.</P ></DD ><DT ><A HREF="ref.script.html" ><SPAN CLASS="PROPERTY" >script</SPAN ></A ></DT ><DD ><P >Include additional configuration information from another CDL script</P ></DD ></DL ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN3255" ></A ><H2 >Example</H2 ><P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >cdl_component CYGDBG_USE_ASSERTS { display "Use asserts" default_value 1 description " If this component is enabled, assertions in the code are tested at run-time. Assert functions (CYG_ASSERT()) are defined in 'include/cyg/infra/cyg_ass.h' within the 'install' tree. If the component is disabled, these result in no additional object code and no checking of the asserted conditions." script assert.cdl }</PRE ></TD ></TR ></TABLE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN3259" ></A ><H2 >See Also</H2 ><P >Command <A HREF="ref.cdl-option.html" ><TT CLASS="LITERAL" >cdl_option</TT ></A >, command <A HREF="ref.cdl-package.html" ><TT CLASS="LITERAL" >cdl_package</TT ></A >, command <A HREF="ref.cdl-interface.html" ><TT CLASS="LITERAL" >cdl_interface</TT ></A >.</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="ref.cdl-option.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="cdl-guide.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="ref.cdl-package.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><TT CLASS="LITERAL" >cdl_option</TT ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="reference.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><TT CLASS="LITERAL" >cdl_package</TT ></TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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