1<!-- HTML header for doxygen 1.8.8--> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="X-UA-Compatible" content="IE=edge"> 6 <!-- For Mobile Devices --> 7 <meta name="viewport" content="width=device-width, initial-scale=1"> 8 <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> 9 <meta name="generator" content="Doxygen 1.9.6"/> 10 <script type="text/javascript" src="https://code.jquery.com/jquery-2.1.1.min.js"></script> 11 <title>libevdev: Compatibility and Behavior across kernel versions</title> 12 <!--<link href="tabs.css" rel="stylesheet" type="text/css"/>--> 13 <script type="text/javascript" src="dynsections.js"></script> 14 <link href="search/search.css" rel="stylesheet" type="text/css"/> 15<script type="text/javascript" src="search/searchdata.js"></script> 16<script type="text/javascript" src="search/search.js"></script> 17 <link href="doxygen.css" rel="stylesheet" type="text/css" /> 18 <link href="bootstrap.css" rel="stylesheet" type="text/css"/> 19<link href="customdoxygen.css" rel="stylesheet" type="text/css"/> 20<link href="libevdevdoxygen.css" rel="stylesheet" type="text/css"/> 21 <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script> 22 <script type="text/javascript" src="doxy-boot.js"></script> 23 </head> 24 <body> 25 <nav class="navbar navbar-default" role="navigation"> 26 <div class="container"> 27 <div class="navbar-header"> 28 <a class="navbar-brand">libevdev 1.13.1</a> 29 </div> 30 </div> 31 </nav> 32 <div id="top"><!-- do not remove this div, it is closed by doxygen! --> 33 <div class="content" id="content"> 34 <div class="container"> 35 <div class="row"> 36 <div class="col-sm-12 panel panel-default" style="padding-bottom: 15px;"> 37 <div style="margin-bottom: 15px;"> 38<!-- end header part --> 39<!-- Generated by Doxygen 1.9.6 --> 40<script type="text/javascript"> 41/* @license magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&dn=expat.txt MIT */ 42var searchBox = new SearchBox("searchBox", "search/",'.html'); 43/* @license-end */ 44</script> 45<script type="text/javascript" src="menudata.js"></script> 46<script type="text/javascript" src="menu.js"></script> 47<script type="text/javascript"> 48/* @license magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&dn=expat.txt MIT */ 49$(function() { 50 initMenu('',true,false,'search.php','Search'); 51 $(document).ready(function() { init_search(); }); 52}); 53/* @license-end */ 54</script> 55<div id="main-nav"></div> 56<!-- window showing the filter options --> 57<div id="MSearchSelectWindow" 58 onmouseover="return searchBox.OnSearchSelectShow()" 59 onmouseout="return searchBox.OnSearchSelectHide()" 60 onkeydown="return searchBox.OnSearchSelectKey(event)"> 61</div> 62 63<!-- iframe showing the search results (closed by default) --> 64<div id="MSearchResultsWindow"> 65<div id="MSearchResults"> 66<div class="SRPage"> 67<div id="SRIndex"> 68<div id="SRResults"></div> 69<div class="SRStatus" id="Loading">Loading...</div> 70<div class="SRStatus" id="Searching">Searching...</div> 71<div class="SRStatus" id="NoMatches">No Matches</div> 72</div> 73</div> 74</div> 75</div> 76 77</div><!-- top --> 78<div><div class="header"> 79 <div class="headertitle"><div class="title">Compatibility and Behavior across kernel versions </div></div> 80</div><!--header--> 81<div class="contents"> 82<div class="textblock"><p>This page describes libevdev's behavior when the build-time kernel and the run-time kernel differ in their feature set.</p> 83<p>With the exception of event names, libevdev defines features that may be missing on older kernels and building on such kernels will not disable features. Running libevdev on a kernel that is missing some feature will change libevdev's behavior. In most cases, the new behavior should be obvious, but it is spelled out below in detail.</p> 84<h1><a class="anchor" id="autotoc_md14"></a> 85Minimum requirements</h1> 86<p>libevdev requires a 2.6.36 kernel as minimum. Specifically, it requires kernel-support for <code>ABS_MT_SLOT</code>.</p> 87<h1><a class="anchor" id="autotoc_md15"></a> 88Event and input property names</h1> 89<p>Event names and input property names are defined at build-time by the linux/input.h shipped with libevdev. The list of event names is compiled at build-time, any events not defined at build time will not resolve. Specifically, <a class="el" href="group__misc.html#ga50a218262738b97044bbffde74c73391">libevdev_event_code_get_name()</a> for an undefined type or code will always return <code>NULL</code>. Likewise, <a class="el" href="group__misc.html#ga78b0893d99b79fe5c92c9e0018ef56be">libevdev_property_get_name()</a> will return NULL for properties undefined at build-time.</p> 90<h1><a class="anchor" id="autotoc_md16"></a> 91Input properties</h1> 92<p>If the kernel does not support input properties, specifically the <code>EVIOCGPROPS</code> ioctl, libevdev does not expose input properties to the caller. Specifically, <a class="el" href="group__bits.html#ga36d529ea53f4522004bc7d16c051464b">libevdev_has_property()</a> will always return 0 unless the property has been manually set with <a class="el" href="group__kernel.html#gafc552080520c9d886452b05f3a1d75b6">libevdev_enable_property()</a>.</p> 93<p>This also applies to the libevdev-uinput code. If uinput does not honor <code>UI_SET_PROPBIT</code>, libevdev will continue without setting the properties on the device.</p> 94<h1><a class="anchor" id="autotoc_md17"></a> 95MT slot behavior</h1> 96<p>If the kernel does not support the <code>EVIOCGMTSLOTS</code> ioctl, libevdev assumes all values in all slots are 0 and continues without an error.</p> 97<h1><a class="anchor" id="autotoc_md18"></a> 98SYN_DROPPED behavior</h1> 99<p>A kernel without <code>SYN_DROPPED</code> won't send such an event. <a class="el" href="group__events.html#gabb96c864e836c0b98788f4ab771c3a76" title="Get the next event from the device.">libevdev_next_event()</a> will never require the switch to sync mode. </p> 100</div></div><!-- contents --> 101</div><!-- PageDoc --> 102<!-- HTML footer for doxygen 1.8.8--> 103<!-- start footer part --> 104</div> 105</div> 106</div> 107</div> 108</div> 109<hr class="footer"/><address class="footer"><small> 110Generated by  <a href="http://www.doxygen.org/index.html"> 111<img class="footer" src="doxygen.png" alt="doxygen"/> 112</a> 1.9.6 113</small></address> 114</body> 115</html> 116
