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

    14 groups</xref> to add new attributes and new types of hardware. </p>

    15 <section id="GUID-7ACAB5F0-08A8-4D53-9F47-9E77642F7337"><title>Extending an existing hardware type</title> <p>Each HAL group

    16 has an associated set of function numbers. For example, the enumerators of <codeph>TDisplayHalFunction</codeph>,

    17 in <filepath>u32std.h</filepath> define the functions associated with the

    18 HAL group <codeph>EHalGroupDisplay</codeph>. </p> <p>In this specific case,

    19 new state can be represented by a new function number, and by changing the <xref href="GUID-9AE254D4-AA60-579E-8D9D-F2797106A413.dita#GUID-9AE254D4-AA60-579E-8D9D-F2797106A413/GUID-1B59A40C-D023-5555-8E5E-DF18D653D321">HAL

    20 handler implementation</xref> to deal with the new function number. </p> <p>It

    21 is important to note that any new function numbers should not follow consecutively

    22 from those defined by Symbian. Instead, choose high values so that they are

    23 guaranteed not to clash with any future Symbian extensions. Symbian will always

    24 use new values that follow consecutively from previous Symbian defined values. </p> </section>

    25 <section id="GUID-A819D9EA-A16F-4806-B8E8-C7ED008C6D31"><title>New hardware type</title> <p>Although up to 32 HAL groups

    26 can be defined, Symbian OS does not use all 32. This leaves some values that

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

    28 at the high end of the range, so that it is guaranteed not to clash with any

    29 future Symbian extensions. Symbian will always use new values that follow

    30 consecutively from previous Symbian defined values. </p> </section>

    31 </conbody></concept>