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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>usb_poison_urb</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="re49.html" title="usb_kill_urb" /><link rel="next" href="re51.html" title="usb_kill_anchored_urbs" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>usb_poison_urb</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re49.html">Prev</a> </td><th width="60%" align="center">Chapter 5. USB Core APIs</th><td width="20%" align="right"> <a accesskey="n" href="re51.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="usb_poison_urb"><a id="API-usb-poison-urb"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_poison_urb —
reliably kill a transfer and prevent further use of an URB
</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">void <b class="fsfunc">usb_poison_urb </b>(</code></td><td>struct urb * <var class="pdparam">urb</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2744816"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>urb</code></em></span></dt><dd><p>
pointer to URB describing a previously submitted request,
may be NULL
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2744843"></a><h2>Description</h2><p>
This routine cancels an in-progress request. It is guaranteed that
upon return all completion handlers will have finished and the URB
will be totally idle and cannot be reused. These features make
this an ideal way to stop I/O in a <code class="function">disconnect</code> callback.
If the request has not already finished or been unlinked
the completion handler will see urb->status == -ENOENT.
</p><p>
After and while the routine runs, attempts to resubmit the URB will fail
with error -EPERM. Thus even if the URB's completion handler always
tries to resubmit, it will not succeed and the URB will become idle.
</p><p>
This routine may not be used in an interrupt context (such as a bottom
half or a completion handler), or when holding a spinlock, or in other
situations where the caller can't <code class="function">schedule</code>.
</p><p>
This routine should not be called by a driver after its disconnect
method has returned.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re49.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="re51.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>usb_kill_urb</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_kill_anchored_urbs</span></td></tr></table></div></body></html>
