1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>usb_altnum_to_altsetting</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux-USB Host Side API"><link rel="up" href="usbcore.html" title="Chapter&#160;5.&#160;USB Core APIs"><link rel="prev" href="API-usb-ifnum-to-if.html" title="usb_ifnum_to_if"><link rel="next" href="API-usb-find-interface.html" title="usb_find_interface"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">usb_altnum_to_altsetting</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-usb-ifnum-to-if.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;5.&#160;USB Core APIs</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-usb-find-interface.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-usb-altnum-to-altsetting"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_altnum_to_altsetting &#8212; 
2     get the altsetting structure with a given alternate setting number.
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">struct usb_host_interface * <b class="fsfunc">usb_altnum_to_altsetting </b>(</code></td><td>const struct usb_interface * <var class="pdparam">intf</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">altnum</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1116476756"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>intf</code></em></span></dt><dd><p>
4     the interface containing the altsetting in question
5    </p></dd><dt><span class="term"><em class="parameter"><code>altnum</code></em></span></dt><dd><p>
6     the desired alternate setting number
7    </p></dd></dl></div></div><div class="refsect1"><a name="idp1116479364"></a><h2>Description</h2><p>
8   This searches the altsetting array of the specified interface for
9   an entry with the correct bAlternateSetting value.
10   </p><p>
11
12   Note that altsettings need not be stored sequentially by number, so
13   it would be incorrect to assume that the first altsetting entry in
14   the array corresponds to altsetting zero.  This routine helps device
15   drivers avoid such mistakes.
16   </p><p>
17
18   Don't call this function unless you are bound to the intf interface
19   or you have locked the device!
20</p></div><div class="refsect1"><a name="idp1116480700"></a><h2>Return</h2><p>
21   A pointer to the entry of the altsetting array of <em class="parameter"><code>intf</code></em> that
22   has <em class="parameter"><code>altnum</code></em> as the alternate setting number. <code class="constant">NULL</code> if not found.
23</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-usb-ifnum-to-if.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="usbcore.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="API-usb-find-interface.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">usb_ifnum_to_if</span>&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;<span class="phrase">usb_find_interface</span></td></tr></table></div></body></html>
24