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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-AF2E227B-C5BD-5F05-98D4-7D15530161C8" xml:lang="en"><title>Interrupt::Clear()</title><shortdesc>Describes the implementation of the clear function.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>The function <xref href="GUID-E7A7083C-97B9-39B9-A147-4A6E314EE3A3.dita#GUID-E7A7083C-97B9-39B9-A147-4A6E314EE3A3/GUID-DB641A23-82B2-373E-A514-E11118CB6E69"><apiname>Interrupt::Clear()</apiname></xref> is used by device drivers
to acknowledge that they have serviced the interrupt and cleared the pending
flag in the interrupt controller hardware. </p>
<p>This is useful in situations where an interrupt must be cleared explicitly
rather than as a side effect of an I/O register access, especially where the
clearing is done from generic code such as in the PC card and MMC controllers. </p>
<p>The implementation of this function is completely dependent on the interrupt
hardware. </p>
<p>In the template port, <codeph>Interrupt::Clear()</codeph> is implemented
in <filepath>...\template_assp\interrupts.cpp</filepath>. </p>
<codeblock id="GUID-7612CEB2-7ADA-552D-9BB9-B0B1B2D8E4BC" xml:space="preserve">EXPORT_C TInt Interrupt::Clear(TInt anId)
    {
     __KTRACE_OPT(KEXTENSION,Kern::Printf("Interrupt::Clear id=%d",anId));
     TInt r=KErrNone;
     // if ID indicates a chained interrupt, call variant...
     if (anId&lt;0 &amp;&amp; ((((TUint)anId)&gt;&gt;16)&amp;0x7fff)&lt;(TUint)KNumTemplateInts)
         r=TemplateAssp::Variant-&gt;InterruptClear(anId);
     else if ((TUint)anId&gt;=(TUint)KNumTemplateInts)
         r=KErrArgument;
     else
         {
         //
         // TO DO: (mandatory)
         //
         // Clear the corresponding Hardware Interrupt source
         //
        }
    return r;
    }</codeblock>
</conbody></concept>