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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 >legal_values</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="include_files" HREF="ref.include-files.html"><LINK REL="NEXT" TITLE="library" HREF="ref.library.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.include-files.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="ref.library.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="REF.LEGAL-VALUES"><SPAN CLASS="PROPERTY" >legal_values</SPAN ></H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN4615" ></A ><H2 >Name</H2 >Property <SPAN CLASS="PROPERTY" >legal_values</SPAN > -- Impose constraints on the possible values for an option.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN4619"><H2 >Synopsis</H2 ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="SYNOPSIS" >cdl_option <name> { legal_values <list expression> … }</PRE ></TD ></TR ></TABLE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4621" ></A ><H2 >Description</H2 ><P >Options with the <TT CLASS="LITERAL" >data</TT > or <TT CLASS="LITERAL" >booldata</TT > flavors can have an arbitrary sequence of characters as their data. In nearly all cases some restrictions have to be imposed, for example the data should correspond to a number within a certain range, or it should be one of a small number of constants. The <SPAN CLASS="PROPERTY" >legal_values</SPAN > property can be used to impose such constraints. The arguments to the property should be a <SPAN CLASS="APPLICATION" >CDL</SPAN > list expression, see <A HREF="language.values.html#LANGUAGE.LIST-EXPRESSION" >the Section called <I >List Expressions</I > in Chapter 3</A > for the syntactic details. Common examples include:</P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" > legal_values 0 to 0x7fff legal_values 9600 19200 38400 legal_values { "RAM" "ROM" }</PRE ></TD ></TR ></TABLE ><P >The <SPAN CLASS="PROPERTY" >legal_values</SPAN > property can only be used for options with the <TT CLASS="LITERAL" >data</TT > or <TT CLASS="LITERAL" >booldata</TT > flavors, since it makes little sense to further constrain the legal values of a boolean option. An option can have at most one <SPAN CLASS="PROPERTY" >legal_values</SPAN > property.</P ><DIV CLASS="TIP" ><BLOCKQUOTE CLASS="TIP" ><P ><B >Tip: </B >If the first entry in a <SPAN CLASS="PROPERTY" >legal_values</SPAN > list expression is a negative number, for example <TT CLASS="LITERAL" >legal_values -1 to 1</TT > then this can be misinterpreted as an option instead of as part of the expression. Currently the <SPAN CLASS="PROPERTY" >legal_values</SPAN > property does not take any options, but this may change in future. Option processing halts at the sequence <TT CLASS="LITERAL" >--</TT >, so the desired range can be expressed safely using <TT CLASS="LITERAL" >legal_values -- -1 to 1</TT ></P ></BLOCKQUOTE ></DIV ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B >Architectural HAL packages should provide constants which can be used in <SPAN CLASS="PROPERTY" >legal_values</SPAN > list expressions. For example it should be possible to specify a numeric range such as <TT CLASS="LITERAL" >0 to CYGARC_MAXINT</TT >, rather than hard-wiring numbers such as <TT CLASS="LITERAL" >0x7fffffff</TT > which may not be valid on all targets. Current HAL packages do not define such constants. </P ></BLOCKQUOTE ></DIV ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B >The <SPAN CLASS="PROPERTY" >legal_values</SPAN > property is restricted mainly to numerical ranges and simple enumerations, and cannot cope with more complicated data items. Future versions of the configuration system will provide additional data validation facilities, for example a <TT CLASS="LITERAL" >check_proc</TT > property which specifies a Tcl script that can be used to perform the validation.</P ></BLOCKQUOTE ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4651" ></A ><H2 >Example</H2 ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >cdl_option CYGNUM_LIBC_TIME_STD_DEFAULT_OFFSET { display "Default Standard Time offset" flavor data legal_values -- -90000 to 90000 default_value -- 0 description " This option controls the offset from UTC in seconds when in local Standard Time. This value can be positive or negative. It can also be set at run time using the cyg_libc_time_setzoneoffsets() function." }</PRE ></TD ></TR ></TABLE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4654" ></A ><H2 >See Also</H2 ><P >Properties <A HREF="ref.calculated.html" ><SPAN CLASS="PROPERTY" >calculated</SPAN ></A >, <A HREF="ref.default-value.html" ><SPAN CLASS="PROPERTY" >default_value</SPAN ></A >, and <A HREF="ref.flavor.html" ><SPAN CLASS="PROPERTY" >flavor</SPAN ></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.include-files.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.library.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><SPAN CLASS="PROPERTY" >include_files</SPAN ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="reference.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><SPAN CLASS="PROPERTY" >library</SPAN ></TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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