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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>parport_wait_peripheral</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Linux Device Drivers" /><link rel="up" href="ch03.html" title="Chapter 3. Parallel Port Devices" /><link rel="prev" href="re278.html" title="parport_wait_event" /><link rel="next" href="re280.html" title="parport_negotiate" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>parport_wait_peripheral</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re278.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Parallel Port Devices</th><td width="20%" align="right"> <a accesskey="n" href="re280.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="parport_wait_peripheral"><a id="API-parport-wait-peripheral"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>parport_wait_peripheral —
wait for status lines to change in 35ms
</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">int <b class="fsfunc">parport_wait_peripheral </b>(</code></td><td>struct parport * <var class="pdparam">port</var>, </td></tr><tr><td> </td><td>unsigned char <var class="pdparam">mask</var>, </td></tr><tr><td> </td><td>unsigned char <var class="pdparam">result</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2634394"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>port</code></em></span></dt><dd><p>
port to watch
</p></dd><dt><span class="term"><em class="parameter"><code>mask</code></em></span></dt><dd><p>
status lines to watch
</p></dd><dt><span class="term"><em class="parameter"><code>result</code></em></span></dt><dd><p>
desired values of chosen status lines
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2634455"></a><h2>Description</h2><p>
This function waits until the masked status lines have the
desired values, or until 35ms have elapsed (see IEEE 1284-1994
page 24 to 25 for why this value in particular is hardcoded).
The <em class="parameter"><code>mask</code></em> and <em class="parameter"><code>result</code></em> parameters are bitmasks, with the bits
defined by the constants in parport.h: <code class="constant">PARPORT_STATUS_BUSY</code>,
and so on.
</p><p>
The port is polled quickly to start off with, in anticipation
of a fast response from the peripheral. This fast polling
time is configurable (using /proc), and defaults to 500usec.
If the timeout for this port (see <code class="function">parport_set_timeout</code>) is
zero, the fast polling time is 35ms, and this function does
not call <code class="function">schedule</code>.
</p><p>
If the timeout for this port is non-zero, after the fast
polling fails it uses <code class="function">parport_wait_event</code> to wait for up to
10ms, waking up if an interrupt occurs.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re278.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch03.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re280.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>parport_wait_event</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>parport_negotiate</span></td></tr></table></div></body></html>
