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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>blk_init_queue</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Linux Kernel API" /><link rel="up" href="ch14.html" title="Chapter 14. Block Devices" /><link rel="prev" href="re505.html" title="blk_run_queue" /><link rel="next" href="re507.html" title="blk_make_request" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>blk_init_queue</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re505.html">Prev</a> </td><th width="60%" align="center">Chapter 14. Block Devices</th><td width="20%" align="right"> <a accesskey="n" href="re507.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="blk_init_queue"><a id="API-blk-init-queue"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_init_queue —
prepare a request queue for use with a block device
</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 request_queue * <b class="fsfunc">blk_init_queue </b>(</code></td><td>request_fn_proc * <var class="pdparam">rfn</var>, </td></tr><tr><td> </td><td>spinlock_t * <var class="pdparam">lock</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3027903"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>rfn</code></em></span></dt><dd><p>
The function to be called to process requests that have been
placed on the queue.
</p></dd><dt><span class="term"><em class="parameter"><code>lock</code></em></span></dt><dd><p>
Request queue spin lock
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3027948"></a><h2>Description</h2><p>
If a block device wishes to use the standard request handling procedures,
which sorts requests and coalesces adjacent requests, then it must
call <code class="function">blk_init_queue</code>. The function <em class="parameter"><code>rfn</code></em> will be called when there
are requests on the queue that need to be processed. If the device
supports plugging, then <em class="parameter"><code>rfn</code></em> may not be called immediately when requests
are available on the queue, but may be called at some time later instead.
Plugged queues are generally unplugged when a buffer belonging to one
of the requests on the queue is needed, or due to memory pressure.
</p><p>
<em class="parameter"><code>rfn</code></em> is not required, or even expected, to remove all requests off the
queue, but only as many as it can handle at a time. If it does leave
requests on the queue, it is responsible for arranging that the requests
get dealt with eventually.
</p><p>
The queue spin lock must be held while manipulating the requests on the
request queue; this lock will be taken also from interrupt context, so irq
disabling is needed for it.
</p><p>
Function returns a pointer to the initialized request queue, or <code class="constant">NULL</code> if
it didn't succeed.
</p></div><div class="refsect1" title="Note"><a id="id3028009"></a><h2>Note</h2><p>
<code class="function">blk_init_queue</code> must be paired with a <code class="function">blk_cleanup_queue</code> call
when the block device is deactivated (such as at module unload).
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re505.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch14.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re507.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>blk_run_queue</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>blk_make_request</span></td></tr></table></div></body></html>
