Changes between Initial Version and Version 1 of linux/backlight

Timestamp:

10/22/2017 05:28:45 AM (6 years ago)

Author:

trac

Comment:

--

linux/backlight

@@ +1 @@
+{{{#!html
+          <div id="wikipage" class="trac-content"><p>
+</p><div class="wiki-toc">
+<ol>
+  <li>
+    <a href="#LinuxBacklightclassdigitaldisplaybacklights">Linux Backlight class digital display backlights</a>
+  </li>
+  <li>
+    <a href="#OtherReferences">Other References</a>
+  </li>
+</ol>
+</div><p>
+</p>
+<p>
+<span class="wikianchor" id="backlight_class"></span>
+</p>
+<h1 id="LinuxBacklightclassdigitaldisplaybacklights">Linux Backlight class digital display backlights</h1>
+<p>
+A digital display which has a backlight may have a Linux backlight driver which provides a sysfs API. Typically these are implemented via PWM signals allowing a variable brightness or a GPIO signal allowing a simple on/off.
+</p>
+<p>
+Mapping A backlight driver to a PWM, GPIO, or other controller is done in the board support file or in the case of more modern kernels such as Ventana in the device-tree. See the backlight node in the <a class="ext-link" href="http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/imx6qdl-gw54xx.dtsi#n31"><span class="icon">​</span>gw54xx device-tree</a> for example.
+</p>
+<p>
+To list available backlight controllers:
+</p>
+<pre class="wiki">ls /sys/class/backlight
+</pre><p>
+To see current/available brightness values:
+</p>
+<pre class="wiki">cat /sys/class/backlight/*/brightness # current brightness
+cat /sys/class/backlight/*/max_brightness # max brightness
+</pre><p>
+To set brightness (to a value equal or less than max_brightness)
+</p>
+<pre class="wiki">echo 0 &gt; /sys/class/backlight/*/brightness # turn off backlight
+</pre><p>
+References:
+</p>
+<ul><li><a class="ext-link" href="http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/leds/backlight/gpio-backlight.txt"><span class="icon">​</span>GPIO backlight</a>
+</li><li><a class="ext-link" href="http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt"><span class="icon">​</span>PWM backlight</a>
+</li><li><a class="ext-link" href="http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/stable/sysfs-class-backlight"><span class="icon">​</span>sysfs-class-backlight</a>
+</li></ul><h1 id="OtherReferences">Other References</h1>
+<p>
+Here are some other useful references from our wiki:
+</p>
+<ul><li><a class="wiki" href="/wiki/gpio">General Purpose I/O (GPIO)</a>
+</li><li><a class="wiki" href="/wiki/linux/pwm">Pulse-Width-Modulation (PWM)</a>
+</li><li><a class="wiki" href="/wiki/OpenWrt/gpio">GPIO in OpenWrt</a>
+</li><li><a class="wiki" href="/wiki/ventana/DigitalIO">Ventana product family Digital I/O</a>
+</li></ul
+}}}