1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>parport_wait_peripheral</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Linux Device Drivers"><link rel="up" href="parportdev.html" title="Chapter&#160;3.&#160;Parallel Port Devices"><link rel="prev" href="API-parport-wait-event.html" title="parport_wait_event"><link rel="next" href="API-parport-negotiate.html" title="parport_negotiate"></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">parport_wait_peripheral</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-parport-wait-event.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;3.&#160;Parallel Port Devices</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-parport-negotiate.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-parport-wait-peripheral"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>parport_wait_peripheral &#8212; 
2     wait for status lines to change in 35ms
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">int <b class="fsfunc">parport_wait_peripheral </b>(</code></td><td>struct parport * <var class="pdparam">port</var>, </td></tr><tr><td>&#160;</td><td>unsigned char <var class="pdparam">mask</var>, </td></tr><tr><td>&#160;</td><td>unsigned char <var class="pdparam">result</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1110915836"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>port</code></em></span></dt><dd><p>
4     port to watch
5    </p></dd><dt><span class="term"><em class="parameter"><code>mask</code></em></span></dt><dd><p>
6     status lines to watch
7    </p></dd><dt><span class="term"><em class="parameter"><code>result</code></em></span></dt><dd><p>
8     desired values of chosen status lines
9    </p></dd></dl></div></div><div class="refsect1"><a name="idp1110919508"></a><h2>Description</h2><p>
10   This function waits until the masked status lines have the
11   desired values, or until 35ms have elapsed (see IEEE 1284-1994
12   page 24 to 25 for why this value in particular is hardcoded).
13   The <em class="parameter"><code>mask</code></em> and <em class="parameter"><code>result</code></em> parameters are bitmasks, with the bits
14   defined by the constants in parport.h: <code class="constant">PARPORT_STATUS_BUSY</code>,
15   and so on.
16   </p><p>
17
18   The port is polled quickly to start off with, in anticipation
19   of a fast response from the peripheral.  This fast polling
20   time is configurable (using /proc), and defaults to 500usec.
21   If the timeout for this port (see <code class="function">parport_set_timeout</code>) is
22   zero, the fast polling time is 35ms, and this function does
23   not call <code class="function">schedule</code>.
24   </p><p>
25
26   If the timeout for this port is non-zero, after the fast
27   polling fails it uses <code class="function">parport_wait_event</code> to wait for up to
28   10ms, waking up if an interrupt occurs.
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