<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><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 V1.75.2" /><link rel="home" href="index.html" title="The Linux-USB Host Side API" /><link rel="up" href="ch05.html" title="Chapter 5. USB Core APIs" /><link rel="prev" href="re58.html" title="usb_anchor_empty" /><link rel="next" href="re60.html" title="usb_interrupt_msg" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>usb_control_msg</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re58.html">Prev</a> </td><th width="60%" align="center">Chapter 5. USB Core APIs</th><td width="20%" align="right"> <a accesskey="n" href="re60.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="usb_control_msg"><a id="API-usb-control-msg"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_control_msg —
Builds a control urb, sends it off and waits for completion
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><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> </td><td>unsigned int <var class="pdparam">pipe</var>, </td></tr><tr><td> </td><td>__u8 <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>__u8 <var class="pdparam">requesttype</var>, </td></tr><tr><td> </td><td>__u16 <var class="pdparam">value</var>, </td></tr><tr><td> </td><td>__u16 <var class="pdparam">index</var>, </td></tr><tr><td> </td><td>void * <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>__u16 <var class="pdparam">size</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">timeout</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3109946"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>dev</code></em></span></dt><dd><p>
pointer to the usb device to send the message to
</p></dd><dt><span class="term"><em class="parameter"><code>pipe</code></em></span></dt><dd><p>
endpoint <span class="quote">“<span class="quote">pipe</span>”</span> to send the message to
</p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>
USB message request value
</p></dd><dt><span class="term"><em class="parameter"><code>requesttype</code></em></span></dt><dd><p>
USB message request type value
</p></dd><dt><span class="term"><em class="parameter"><code>value</code></em></span></dt><dd><p>
USB message value
</p></dd><dt><span class="term"><em class="parameter"><code>index</code></em></span></dt><dd><p>
USB message index value
</p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
pointer to the data to send
</p></dd><dt><span class="term"><em class="parameter"><code>size</code></em></span></dt><dd><p>
length in bytes of the data to send
</p></dd><dt><span class="term"><em class="parameter"><code>timeout</code></em></span></dt><dd><p>
time in msecs to wait for the message to complete before timing
out (if 0 the wait is forever)
</p></dd></dl></div></div><div class="refsect1" title="Context"><a id="id3110110"></a><h2>Context</h2><p>
!in_interrupt ()
</p></div><div class="refsect1" title="Description"><a id="id3110119"></a><h2>Description</h2><p>
This function sends a simple control message to a specified endpoint and
waits for the message to complete, or timeout.
</p><p>
If successful, it returns the number of bytes transferred, otherwise a
negative error number.
</p><p>
Don't use this function from within an interrupt context, like a bottom half
handler. If you need an asynchronous message, or need to send a message
from within interrupt context, use <code class="function">usb_submit_urb</code>.
If a thread in your driver uses this call, make sure your <code class="function">disconnect</code>
method can wait for it to complete. Since you don't have a handle on the
URB used, you can't cancel the request.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re58.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch05.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re60.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>usb_anchor_empty</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>usb_interrupt_msg</span></td></tr></table></div></body></html>
