1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>drm_dp_dpcd_read</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Linux DRM Developer's Guide"><link rel="up" href="ch02s05.html#idp1125808116" title="Display Port Helper Functions Reference"><link rel="prev" href="API-drm-dp-dpcd-writeb.html" title="drm_dp_dpcd_writeb"><link rel="next" href="API-drm-dp-dpcd-write.html" title="drm_dp_dpcd_write"></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">drm_dp_dpcd_read</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-drm-dp-dpcd-writeb.html">Prev</a>&#160;</td><th width="60%" align="center">Display Port Helper Functions Reference</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-drm-dp-dpcd-write.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-drm-dp-dpcd-read"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>drm_dp_dpcd_read &#8212; 
2  read a series of bytes from the DPCD
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">ssize_t <b class="fsfunc">drm_dp_dpcd_read </b>(</code></td><td>struct drm_dp_aux * <var class="pdparam">aux</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">offset</var>, </td></tr><tr><td>&#160;</td><td>void * <var class="pdparam">buffer</var>, </td></tr><tr><td>&#160;</td><td>size_t <var class="pdparam">size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1125859164"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>aux</code></em></span></dt><dd><p>
4     DisplayPort AUX channel
5    </p></dd><dt><span class="term"><em class="parameter"><code>offset</code></em></span></dt><dd><p>
6     address of the (first) register to read
7    </p></dd><dt><span class="term"><em class="parameter"><code>buffer</code></em></span></dt><dd><p>
8     buffer to store the register values
9    </p></dd><dt><span class="term"><em class="parameter"><code>size</code></em></span></dt><dd><p>
10     number of bytes in <em class="parameter"><code>buffer</code></em>
11    </p></dd></dl></div></div><div class="refsect1"><a name="idp1125864164"></a><h2>Description</h2><p>
12   Returns the number of bytes transferred on success, or a negative error
13   code on failure. -EIO is returned if the request was NAKed by the sink or
14   if the retry count was exceeded. If not all bytes were transferred, this
15   function returns -EPROTO. Errors from the underlying AUX channel transfer
16   function, with the exception of -EBUSY (which causes the transaction to
17   be retried), are propagated to the caller.
18</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-drm-dp-dpcd-writeb.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="ch02s05.html#idp1125808116">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="API-drm-dp-dpcd-write.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">drm_dp_dpcd_writeb</span>&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;<span class="phrase">drm_dp_dpcd_write</span></td></tr></table></div></body></html>
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