<!DOCTYPE html>
<html lang="en" data-content_root="../">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />
<title>3. Keyboard notifier — The Linux Kernel documentation</title>
<link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=fa44fd50" />
<link rel="stylesheet" type="text/css" href="../_static/alabaster.css?v=3918102e" />
<script src="../_static/documentation_options.js?v=5929fcd5"></script>
<script src="../_static/doctools.js?v=9bcbadda"></script>
<script src="../_static/sphinx_highlight.js?v=dc90522c"></script>
<link rel="index" title="Index" href="../genindex.html" />
<link rel="search" title="Search" href="../search.html" />
<link rel="next" title="Driver-specific documentation" href="devices/index.html" />
<link rel="prev" title="2. Programming gameport drivers" href="gameport-programming.html" />
<link rel="stylesheet" href="../_static/custom.css" type="text/css" />
</head><body>
<div class="document">
<div class="sphinxsidebar" role="navigation" aria-label="Main">
<div class="sphinxsidebarwrapper">
<p class="logo"><a href="../index.html">
<img class="logo" src="../_static/logo.svg" alt="Logo of The Linux Kernel"/>
</a></p>
<h1 class="logo"><a href="../index.html">The Linux Kernel</a></h1>
<p class="blurb">6.18.50</p>
<search id="searchbox" style="display: none" role="search">
<h3 id="searchlabel">Quick search</h3>
<div class="searchformwrapper">
<form class="search" action="../search.html" method="get">
<input type="text" name="q" aria-labelledby="searchlabel" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"/>
<input type="submit" value="Go" />
</form>
</div>
</search>
<script>document.getElementById('searchbox').style.display = "block"</script>
<p>
<h3 class="kernel-toc-contents">Contents</h3>
<input type="checkbox" class="kernel-toc-toggle" id = "kernel-toc-toggle" checked>
<label class="kernel-toc-title" for="kernel-toc-toggle"></label>
<div class="kerneltoc" id="kerneltoc">
<ul>
<li class="toctree-l1"><a class="reference internal" href="../process/development-process.html">Development process</a></li>
<li class="toctree-l1"><a class="reference internal" href="../process/submitting-patches.html">Submitting patches</a></li>
<li class="toctree-l1"><a class="reference internal" href="../process/code-of-conduct.html">Code of conduct</a></li>
<li class="toctree-l1"><a class="reference internal" href="../maintainer/index.html">Maintainer handbook</a></li>
<li class="toctree-l1"><a class="reference internal" href="../process/index.html">All development-process docs</a></li>
</ul>
<ul class="current">
<li class="toctree-l1"><a class="reference internal" href="../core-api/index.html">Core API</a></li>
<li class="toctree-l1"><a class="reference internal" href="../driver-api/index.html">Driver APIs</a></li>
<li class="toctree-l1 current"><a class="reference internal" href="../subsystem-apis.html">Subsystems</a><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="../subsystem-apis.html#core-subsystems">Core subsystems</a></li>
<li class="toctree-l2 current"><a class="reference internal" href="../subsystem-apis.html#human-interfaces">Human interfaces</a><ul class="current">
<li class="toctree-l3 current"><a class="reference internal" href="index.html">Input Documentation</a></li>
<li class="toctree-l3"><a class="reference internal" href="../hid/index.html">Human Interface Devices (HID)</a></li>
<li class="toctree-l3"><a class="reference internal" href="../sound/index.html">Sound Subsystem Documentation</a></li>
<li class="toctree-l3"><a class="reference internal" href="../gpu/index.html">GPU Driver Developer’s Guide</a></li>
<li class="toctree-l3"><a class="reference internal" href="../fb/index.html">Frame Buffer</a></li>
<li class="toctree-l3"><a class="reference internal" href="../leds/index.html">LEDs</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../subsystem-apis.html#networking-interfaces">Networking interfaces</a></li>
<li class="toctree-l2"><a class="reference internal" href="../subsystem-apis.html#storage-interfaces">Storage interfaces</a></li>
<li class="toctree-l2"><a class="reference internal" href="../subsystem-apis.html#other-subsystems">Other subsystems</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../locking/index.html">Locking</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../process/license-rules.html">Licensing rules</a></li>
<li class="toctree-l1"><a class="reference internal" href="../doc-guide/index.html">Writing documentation</a></li>
<li class="toctree-l1"><a class="reference internal" href="../dev-tools/index.html">Development tools</a></li>
<li class="toctree-l1"><a class="reference internal" href="../dev-tools/testing-overview.html">Testing guide</a></li>
<li class="toctree-l1"><a class="reference internal" href="../kernel-hacking/index.html">Hacking guide</a></li>
<li class="toctree-l1"><a class="reference internal" href="../trace/index.html">Tracing</a></li>
<li class="toctree-l1"><a class="reference internal" href="../fault-injection/index.html">Fault injection</a></li>
<li class="toctree-l1"><a class="reference internal" href="../livepatch/index.html">Livepatching</a></li>
<li class="toctree-l1"><a class="reference internal" href="../rust/index.html">Rust</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../admin-guide/index.html">Administration</a></li>
<li class="toctree-l1"><a class="reference internal" href="../kbuild/index.html">Build system</a></li>
<li class="toctree-l1"><a class="reference internal" href="../admin-guide/reporting-issues.html">Reporting issues</a></li>
<li class="toctree-l1"><a class="reference internal" href="../tools/index.html">Userspace tools</a></li>
<li class="toctree-l1"><a class="reference internal" href="../userspace-api/index.html">Userspace API</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../firmware-guide/index.html">Firmware</a></li>
<li class="toctree-l1"><a class="reference internal" href="../devicetree/index.html">Firmware and Devicetree</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../arch/index.html">CPU architectures</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../staging/index.html">Unsorted documentation</a></li>
</ul>
<ul>
<li class="toctree-l1"><a class="reference internal" href="../translations/index.html">Translations</a></li>
</ul>
</div>
<script type="text/javascript"> <!--
var sbar = document.getElementsByClassName("sphinxsidebar")[0];
let currents = document.getElementsByClassName("current")
if (currents.length) {
sbar.scrollTop = currents[currents.length - 1].offsetTop;
}
--> </script>
<div role="note" aria-label="source link">
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../_sources/input/notifier.rst.txt"
rel="nofollow">Show Source</a></li>
</ul>
</div>
</div>
</div>
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body" role="main">
<section id="keyboard-notifier">
<h1><span class="section-number">3. </span>Keyboard notifier<a class="headerlink" href="#keyboard-notifier" title="Link to this heading">¶</a></h1>
<p>One can use register_keyboard_notifier to get called back on keyboard
events (see <code class="xref c c-func broken_xref docutils literal notranslate"><span class="pre">kbd_keycode()</span></code> function for details). The passed structure is
keyboard_notifier_param (see <linux/keyboard.h>):</p>
<ul class="simple">
<li><p>‘vc’ always provide the VC for which the keyboard event applies;</p></li>
<li><p>‘down’ is 1 for a key press event, 0 for a key release;</p></li>
<li><p>‘shift’ is the current modifier state, mask bit indexes are KG_*;</p></li>
<li><p>‘ledstate’ is the current LED state;</p></li>
<li><p>‘value’ depends on the type of event.</p></li>
<li><p>KBD_KEYCODE events are always sent before other events, value is the keycode.</p></li>
<li><p>KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
value is the keycode.</p></li>
<li><p>KBD_UNICODE events are sent if the keycode -> keysym translation produced a
unicode character. value is the unicode value.</p></li>
<li><p>KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
non-unicode character. value is the keysym.</p></li>
<li><p>KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
That permits one to inspect the resulting LEDs for instance.</p></li>
</ul>
<p>For each kind of event but the last, the callback may return NOTIFY_STOP in
order to “eat” the event: the notify loop is stopped and the keyboard event is
dropped.</p>
<p>In a rough C snippet, we have:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>kbd_keycode(keycode) {
...
params.value = keycode;
if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
|| !bound) {
notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
return;
}
if (unicode) {
param.value = unicode;
if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
return;
emit unicode;
return;
}
params.value = keysym;
if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
return;
apply keysym;
notifier_call_chain(KBD_POST_KEYSYM,&params);
}
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This notifier is usually called from interrupt context.</p>
</div>
</section>
</div>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="footer">
©The kernel development community.
|
Powered by <a href="https://www.sphinx-doc.org/">Sphinx 8.1.3</a>
& <a href="https://alabaster.readthedocs.io">Alabaster 0.7.16</a>
|
<a href="../_sources/input/notifier.rst.txt"
rel="nofollow">Page source</a>
</div>
</body>
</html>