1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>usb_control_msg</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-anchor-empty.html" title="usb_anchor_empty"><link rel="next" href="API-usb-interrupt-msg.html" title="usb_interrupt_msg"></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_control_msg</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-usb-anchor-empty.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-interrupt-msg.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-usb-control-msg"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_control_msg &#8212; 
2  Builds a control urb, sends it off and waits for completion
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">int <b class="fsfunc">usb_control_msg </b>(</code></td><td>struct usb_device * <var class="pdparam">dev</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">pipe</var>, </td></tr><tr><td>&#160;</td><td>__u8 <var class="pdparam">request</var>, </td></tr><tr><td>&#160;</td><td>__u8 <var class="pdparam">requesttype</var>, </td></tr><tr><td>&#160;</td><td>__u16 <var class="pdparam">value</var>, </td></tr><tr><td>&#160;</td><td>__u16 <var class="pdparam">index</var>, </td></tr><tr><td>&#160;</td><td>void * <var class="pdparam">data</var>, </td></tr><tr><td>&#160;</td><td>__u16 <var class="pdparam">size</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">timeout</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1116115548"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>dev</code></em></span></dt><dd><p>
4     pointer to the usb device to send the message to
5    </p></dd><dt><span class="term"><em class="parameter"><code>pipe</code></em></span></dt><dd><p>
6     endpoint <span class="quote">&#8220;<span class="quote">pipe</span>&#8221;</span> to send the message to
7    </p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>
8     USB message request value
9    </p></dd><dt><span class="term"><em class="parameter"><code>requesttype</code></em></span></dt><dd><p>
10     USB message request type value
11    </p></dd><dt><span class="term"><em class="parameter"><code>value</code></em></span></dt><dd><p>
12     USB message value
13    </p></dd><dt><span class="term"><em class="parameter"><code>index</code></em></span></dt><dd><p>
14     USB message index value
15    </p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
16     pointer to the data to send
17    </p></dd><dt><span class="term"><em class="parameter"><code>size</code></em></span></dt><dd><p>
18     length in bytes of the data to send
19    </p></dd><dt><span class="term"><em class="parameter"><code>timeout</code></em></span></dt><dd><p>
20     time in msecs to wait for the message to complete before timing
21     out (if 0 the wait is forever)
22    </p></dd></dl></div></div><div class="refsect1"><a name="idp1116125348"></a><h2>Context</h2><p>
23   !in_interrupt ()
24</p></div><div class="refsect1"><a name="idp1116125924"></a><h2>Description</h2><p>
25   This function sends a simple control message to a specified endpoint and
26   waits for the message to complete, or timeout.
27   </p><p>
28
29   Don't use this function from within an interrupt context, like a bottom half
30   handler.  If you need an asynchronous message, or need to send a message
31   from within interrupt context, use <code class="function">usb_submit_urb</code>.
32   If a thread in your driver uses this call, make sure your <code class="function">disconnect</code>
33   method can wait for it to complete.  Since you don't have a handle on the
34   URB used, you can't cancel the request.
35</p></div><div class="refsect1"><a name="idp1116127796"></a><h2>Return</h2><p>
36   If successful, the number of bytes transferred. Otherwise, a negative
37   error number.
38</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-anchor-empty.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-interrupt-msg.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">usb_anchor_empty</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_interrupt_msg</span></td></tr></table></div></body></html>
39