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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_buffer_map</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="re98.html" title="usb_buffer_free" /><link rel="next" href="re100.html" title="usb_buffer_dmasync" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>usb_buffer_map</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re98.html">Prev</a> </td><th width="60%" align="center">Chapter 5. USB Core APIs</th><td width="20%" align="right"> <a accesskey="n" href="re100.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="usb_buffer_map"><a id="API-usb-buffer-map"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_buffer_map —
create DMA mapping(s) for 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">struct urb * <b class="fsfunc">usb_buffer_map </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="id2752921"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>urb</code></em></span></dt><dd><p>
urb whose transfer_buffer/setup_packet will be mapped
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2752948"></a><h2>Description</h2><p>
Return value is either null (indicating no buffer could be mapped), or
the parameter. URB_NO_TRANSFER_DMA_MAP and URB_NO_SETUP_DMA_MAP are
added to urb->transfer_flags if the operation succeeds. If the device
is connected to this system through a non-DMA controller, this operation
always succeeds.
</p><p>
This call would normally be used for an urb which is reused, perhaps
as the target of a large periodic transfer, with <code class="function">usb_buffer_dmasync</code>
calls to synchronize memory and dma state.
</p><p>
Reverse the effect of this call with <code class="function">usb_buffer_unmap</code>.
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