1<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>blk_init_queue</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux Kernel API"><link rel="up" href="blkdev.html" title="Chapter 14. Block Devices"><link rel="prev" href="API-blk-cleanup-queue.html" title="blk_cleanup_queue"><link rel="next" href="API-blk-make-request.html" title="blk_make_request"></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">blk_init_queue</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-blk-cleanup-queue.html">Prev</a> </td><th width="60%" align="center">Chapter 14. Block Devices</th><td width="20%" align="right"> <a accesskey="n" href="API-blk-make-request.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-blk-init-queue"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_init_queue — 2 prepare a request queue for use with a block device 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">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"><a name="id-1.16.15.5"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>rfn</code></em></span></dt><dd><p> 4 The function to be called to process requests that have been 5 placed on the queue. 6 </p></dd><dt><span class="term"><em class="parameter"><code>lock</code></em></span></dt><dd><p> 7 Request queue spin lock 8 </p></dd></dl></div></div><div class="refsect1"><a name="id-1.16.15.6"></a><h2>Description</h2><p> 9 If a block device wishes to use the standard request handling procedures, 10 which sorts requests and coalesces adjacent requests, then it must 11 call <code class="function"><a class="link" href="API-blk-init-queue.html" title="blk_init_queue">blk_init_queue</a></code>. The function <em class="parameter"><code>rfn</code></em> will be called when there 12 are requests on the queue that need to be processed. If the device 13 supports plugging, then <em class="parameter"><code>rfn</code></em> may not be called immediately when requests 14 are available on the queue, but may be called at some time later instead. 15 Plugged queues are generally unplugged when a buffer belonging to one 16 of the requests on the queue is needed, or due to memory pressure. 17 </p><p> 18 19 <em class="parameter"><code>rfn</code></em> is not required, or even expected, to remove all requests off the 20 queue, but only as many as it can handle at a time. If it does leave 21 requests on the queue, it is responsible for arranging that the requests 22 get dealt with eventually. 23 </p><p> 24 25 The queue spin lock must be held while manipulating the requests on the 26 request queue; this lock will be taken also from interrupt context, so irq 27 disabling is needed for it. 28 </p><p> 29 30 Function returns a pointer to the initialized request queue, or <code class="constant">NULL</code> if 31 it didn't succeed. 32</p></div><div class="refsect1"><a name="id-1.16.15.7"></a><h2>Note</h2><p> 33 <code class="function"><a class="link" href="API-blk-init-queue.html" title="blk_init_queue">blk_init_queue</a></code> must be paired with a <code class="function"><a class="link" href="API-blk-cleanup-queue.html" title="blk_cleanup_queue">blk_cleanup_queue</a></code> call 34 when the block device is deactivated (such as at module unload). 35</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-blk-cleanup-queue.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="blkdev.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="API-blk-make-request.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">blk_cleanup_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 class="phrase">blk_make_request</span></td></tr></table></div></body></html> 36