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    <a href="#LinuxBacklightclassdigitaldisplaybacklights">Linux Backlight class digital display backlights</a>
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    <a href="#OtherReferences">Other References</a>
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<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.
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<p>
To list available backlight controllers:
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<pre class="wiki">ls /sys/class/backlight
</pre><p>
To see current/available brightness values:
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<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)
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<pre class="wiki">echo 0 &gt; /sys/class/backlight/*/brightness # turn off backlight
</pre><p>
References:
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<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
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