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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 >Configuration Items</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos User Guide" HREF="ecos-user-guide.html"><LINK REL="UP" TITLE="CDL Concepts" HREF="cdl-concepts.html"><LINK REL="PREVIOUS" TITLE="Packages" HREF="cdl-packages.html"><LINK REL="NEXT" TITLE="Conflicts" HREF="cdl-conflicts.html"></HEAD ><BODY CLASS="SECT1" 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" >eCos User Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="cdl-packages.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 24. CDL Concepts</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="cdl-conflicts.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="CDL-CONFIGURATION-ITEMS">Configuration Items</H1 ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Configuration items</I ></SPAN > are the individual entities that form a configuration. Each item corresponds to the setting of a C pre-processor macro (for example, <TT CLASS="LITERAL" >CYGHWR_HAL_ARM_PID_GDB_BAUD</TT >). The code of <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > itself is written to test such pre-processor macros so as to tailor the code. User code can do likewise.</P ><P >Configuration items come in the following flavors:</P ><P ></P ><UL ><LI ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >None</I ></SPAN >: such entities serve only as place holders in the hierarchy, allowing other entities to be grouped more easily.</P ></LI ><LI ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Boolean</I ></SPAN > entities are the most common flavor; they correspond to units of functionality that can be either enabled or disabled. If the entity is enabled then there will be a #define; code will check the setting using, for example, #ifdef</P ></LI ><LI ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Data</I ></SPAN > entities encapsulate some arbitrary data. Other properties such as a set or range of legal values can be used to constrain the actual values, for example to an integer or floating point value within a certain range.</P ></LI ><LI ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Booldata</I ></SPAN > entities combine the attributes of <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Boolean</I ></SPAN > and <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Data</I ></SPAN >: they can be enabled or disabled and, if enabled, will hold a data value.</P ></LI ></UL ><P >Like packages, configuration items exist in a tree-based hierarchy: each configuration item has a parent which may be another configuration item or a package. Under some conditions (such as when packages are added or removed from a configuration), items may be “re-parented” such that their position in the tree changes. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1898">Expressions</H2 ><P >Expressions are relationships between CDL items. There are three types of expression in CDL:</P ><DIV CLASS="TABLE" ><A NAME="CDL-EXPRESSIONS"><P ><B >Table 24-1. CDL Expressions</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><THEAD ><TR ><TH ALIGN="LEFT" VALIGN="TOP" >Expression Type</TH ><TH ALIGN="LEFT" VALIGN="TOP" >Result</TH ><TH ALIGN="LEFT" VALIGN="TOP" >Common Use (see <A HREF="cdl-configuration-items.html#TABLE-CONFIGURATION-PROPERTIES" >Table 24-2</A >)</TH ></TR ></THEAD ><TBODY ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Ordinary</TD ><TD ALIGN="LEFT" VALIGN="TOP" >A single value</TD ><TD ALIGN="LEFT" VALIGN="TOP" >legal_values property</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >List</TD ><TD ALIGN="LEFT" VALIGN="TOP" >A range of values (for example “1 to 10”)</TD ><TD ALIGN="LEFT" VALIGN="TOP" >legal_values property </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Goal</TD ><TD ALIGN="LEFT" VALIGN="TOP" >True or False</TD ><TD ALIGN="LEFT" VALIGN="TOP" >requires and active_if properties</TD ></TR ></TBODY ></TABLE ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1923">Properties</H2 ><P >Each configuration item has a set of properties. The following table describes the most commonly used:</P ><DIV CLASS="TABLE" ><A NAME="TABLE-CONFIGURATION-PROPERTIES"><P ><B >Table 24-2. Configuration properties</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><THEAD ><TR ><TH ALIGN="LEFT" VALIGN="TOP" ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Property</I ></SPAN ></TH ><TH ALIGN="LEFT" VALIGN="TOP" ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Use </I ></SPAN ></TH ></TR ></THEAD ><TBODY ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Flavor</TD ><TD ALIGN="LEFT" VALIGN="TOP" >The “type” of the item, as described above </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Enabled</TD ><TD ALIGN="LEFT" VALIGN="TOP" >Whether the item is enabled </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Current_value</TD ><TD ALIGN="LEFT" VALIGN="TOP" >The current value of the item </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Default_value</TD ><TD ALIGN="LEFT" VALIGN="TOP" >An ordinary expression defining the default value of the item</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Legal_values</TD ><TD ALIGN="LEFT" VALIGN="TOP" >A list expression defining the values the item may hold (for example, 1 to10) </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Active_if</TD ><TD ALIGN="LEFT" VALIGN="TOP" >A goal expression denoting the requirement for this item to be active (see below: <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Inactive Items</I ></SPAN >) </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Requires</TD ><TD ALIGN="LEFT" VALIGN="TOP" >A goal expression denoting requirements this item places on others (see below: <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Conflicts</I ></SPAN >) </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Calculated</TD ><TD ALIGN="LEFT" VALIGN="TOP" >Whether the item as non-modifiable </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Macro</TD ><TD ALIGN="LEFT" VALIGN="TOP" >The corresponding C pre-processor macro </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >File</TD ><TD ALIGN="LEFT" VALIGN="TOP" >The C header file in which the macro is defined </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >URL</TD ><TD ALIGN="LEFT" VALIGN="TOP" >The URL of a documentation page describing the item </TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" >Hardware</TD ><TD ALIGN="LEFT" VALIGN="TOP" >Indicates that a particular package is related to specific hardware</TD ></TR ></TBODY ></TABLE ></DIV ><P >A complete description of properties is contained in the <I CLASS="CITETITLE" >Component Writer’s Guide</I >.</P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1976">Inactive Items</H2 ><P >Descendants of an item that is disabled are inactive: their values may not be changed. Items may also become <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >inactive</I ></SPAN > if an active_if expression is used to make the item dependent on an expression involving other items. </P ></DIV ></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="cdl-packages.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-user-guide.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="cdl-conflicts.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Packages</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="cdl-concepts.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Conflicts</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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