asdk-libdrm

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<!--

  Written 2012 by David Herrmann <dh.herrmann@googlemail.com>

  Dedicated to the Public Domain

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<refentry id="drm-kms">

  <refentryinfo>

    <title>Direct Rendering Manager</title>

    <productname>libdrm</productname>

    <date>September 2012</date>

    <authorgroup>

      <author>

        <contrib>Developer</contrib>

        <firstname>David</firstname>

        <surname>Herrmann</surname>

        <email>dh.herrmann@googlemail.com</email>

      </author>

    </authorgroup>

  </refentryinfo>

​

  <refmeta>

    <refentrytitle>drm-kms</refentrytitle>

    <manvolnum>7</manvolnum>

  </refmeta>

​

  <refnamediv>

    <refname>drm-kms</refname>

    <refpurpose>Kernel Mode-Setting</refpurpose>

  </refnamediv>

​

  <refsynopsisdiv>

    <funcsynopsis>

      <funcsynopsisinfo>#include &lt;xf86drm.h&gt;</funcsynopsisinfo>

      <funcsynopsisinfo>#include &lt;xf86drmMode.h&gt;</funcsynopsisinfo>

    </funcsynopsis>

  </refsynopsisdiv>

​

  <refsect1>

    <title>Description</title>

    <para>Each DRM device provides access to manage which monitors and displays

          are currently used and what frames to be displayed. This task is

          called <emphasis>Kernel Mode-Setting</emphasis> (KMS). Historically,

          this was done in user-space and called 

          <emphasis>User-space Mode-Setting</emphasis> (UMS). Almost all

          open-source drivers now provide the KMS kernel API to do this in the

          kernel, however, many non-open-source binary drivers from different

          vendors still do not support this. You can use

          <citerefentry><refentrytitle>drmModeSettingSupported</refentrytitle><manvolnum>3</manvolnum></citerefentry>

          to check whether your driver supports this. To understand how KMS

          works, we need to introduce 5 objects: <emphasis>CRTCs</emphasis>,

          <emphasis>Planes</emphasis>, <emphasis>Encoders</emphasis>,

          <emphasis>Connectors</emphasis> and

          <emphasis>Framebuffers</emphasis>.

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      <variablelist>

        <varlistentry>

          <term>CRTCs</term>

          <listitem>

            <para>A <emphasis>CRTC</emphasis> short for