1 <?xml version="1.0" encoding="utf-8"?>

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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-C661B40F-1439-587F-9E8E-DB2DFC79C040" xml:lang="en"><title>HAL Groups</title><shortdesc>Description of HAL groups to add new attributes.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    13 <p>You can extend <xref href="GUID-9AE254D4-AA60-579E-8D9D-F2797106A413.dita#GUID-9AE254D4-AA60-579E-8D9D-F2797106A413/GUID-366CC4B8-C6BD-5DCC-B55D-6D87CD5C8E64">HAL groups</xref> to add new attributes and new types of hardware. </p>

    14 <section id="GUID-7ACAB5F0-08A8-4D53-9F47-9E77642F7337"><title>Extending

    15 an existing hardware type</title> <p>Each HAL group has an associated

    16 set of function numbers. For example, the enumerators of <codeph>TDisplayHalFunction</codeph>, in <filepath>u32std.h</filepath> define the functions associated

    17 with the HAL group <codeph>EHalGroupDisplay</codeph>. </p> <p>In this

    18 specific case, new state can be represented by a new function number,

    19 and by changing the <xref href="GUID-124AC7EE-E227-5358-A755-628FFE257250.dita">HAL handler implementation</xref> to deal with the new function number. </p> <p>It is

    20 important to note that any new function numbers should not follow

    21 consecutively from those defined by Symbian. Instead, choose high

    22 values so that they are guaranteed not to clash with any future Symbian

    23 extensions. Symbian will always use new values that follow consecutively

    24 from previous Symbian defined values. </p> </section>

    25 <section id="GUID-A819D9EA-A16F-4806-B8E8-C7ED008C6D31"><title>New

    26 hardware type</title> <p>Although up to 32 HAL groups can be defined,

    27 Symbian platform does not use all 32. This leaves some values that

    28 can be used for new hardware. </p> <p>In this case choose a HAL group

    29 number at the high end of the range, so that it is guaranteed not

    30 to clash with any future Symbian extensions. Symbian will always use

    31 new values that follow consecutively from previous Symbian defined

    32 values. </p> </section>

    33 </conbody></concept>