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<concept id="GUID-02B40662-B5F3-59BD-832B-9A28FE3B51C7" xml:lang="en"><title>Debug</title><shortdesc>This topic describes how to use debug messages in the USB
client controller.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>As the USB PDD runs in kernel mode, debug <codeph>printf</codeph> are implemented using the <codeph>KTRACE</codeph> macro.
This macro takes two arguments: </p>
<ul>
<li id="GUID-E3A1AA52-12D9-58EE-A459-46FAA7F5001C"><p>The debug message
type </p> </li>
<li id="GUID-2D7B1C30-563C-5346-8DBC-943839008874"><p>A kernel object
that takes a message string as a constructor. </p> </li>
</ul>
<p>Two debug message types are used: </p>
<ul>
<li id="GUID-962DAE50-32C5-53AB-A203-E08CA57252D5"><p> <codeph>KPANIC</codeph> for error messages </p> </li>
<li id="GUID-6F6409F4-37B1-5713-A763-61B477545706"><p> <codeph>KUSBPSL</codeph> for PSL information messages </p> </li>
</ul>
<p>The following code samples illustrate their use: </p>
<codeblock id="GUID-A130740F-20FA-5825-9BDB-9CE234971757" xml:space="preserve">_KTRACE_OPT(KPANIC, Kern::Printf("Error: USB Controller not present"));</codeblock>
<codeblock id="GUID-6A8812CE-791C-5C62-AC67-29FF5098D9E4" xml:space="preserve">_KTRACE_OPT(KUSBPSL, Kern::Printf("Received new Ep0 Setup packet"));</codeblock>
<note>Do not use the <codeph>KUSB</codeph> flag. This flag is used
within the PDD PIL and the USB LDD only.</note>
</conbody></concept>