path: root/Documentation/DocBook/media/dvb/frontend.xml

<title>DVB Frontend API</title>

<para>The DVB frontend API was designed to support three types of delivery systems:</para>
<itemizedlist>
    <listitem><para>Terrestrial systems: DVB-T, DVB-T2, ATSC, ATSC M/H, ISDB-T, DVB-H, DTMB, CMMB</para></listitem>
    <listitem><para>Cable systems: DVB-C Annex A/C, ClearQAM (DVB-C Annex B), ISDB-C</para></listitem>
    <listitem><para>Satellite systems: DVB-S, DVB-S2, DVB Turbo, ISDB-S, DSS</para></listitem>
</itemizedlist>
<para>The DVB frontend controls several sub-devices including:</para>
<itemizedlist>
    <listitem><para>Tuner</para></listitem>
    <listitem><para>Digital TV demodulator</para></listitem>
    <listitem><para>Low noise amplifier (LNA)</para></listitem>
    <listitem><para>Satellite Equipment Control (SEC) hardware (only for Satellite).</para></listitem>
</itemizedlist>
<para>The frontend can be accessed through
    <constant>/dev/dvb/adapter?/frontend?</constant>. Data types and
    ioctl definitions can be accessed by including
    <constant>linux/dvb/frontend.h</constant> in your application.
</para>

<para>NOTE: Transmission via the internet (DVB-IP)
    is not yet handled by this API but a future extension is possible.</para>
<para>On Satellite systems, the API support for the Satellite Equipment Control
    (SEC) allows to power control and to send/receive signals to control the
    antenna subsystem, selecting the polarization and choosing the Intermediate
    Frequency IF) of the Low Noise Block Converter Feed Horn (LNBf). It
    supports the DiSEqC and V-SEC protocols. The DiSEqC (digital SEC)
specification is available at
<ulink url="http://www.eutelsat.com/satellites/4_5_5.html">Eutelsat</ulink>.</para>

<section id="query-dvb-frontend-info">
<title>Querying frontend information</title>

<para>Usually, the first thing to do when the frontend is opened is to
    check the frontend capabilities. This is done using <link linkend="FE_GET_INFO">FE_GET_INFO</link>. This ioctl will enumerate
    the DVB API version and other characteristics about the frontend, and
    can be opened either in read only or read/write mode.</para>
</section>

<section id="dvb-fe-read-status">
<title>Querying frontend status and statistics</title>

<para>Once <link linkend="FE_GET_PROPERTY"><constant>FE_SET_PROPERTY</constant></link>
    is called, the frontend will run a kernel thread that will periodically
    check for the tuner lock status and provide statistics about the quality
    of the signal.</para>
<para>The information about the frontend tuner locking status can be queried
    using <link linkend="FE_READ_STATUS">FE_READ_STATUS</link>.</para>
<para>Signal statistics are provided via <link linkend="FE_GET_PROPERTY"><constant>FE_GET_PROPERTY</constant></link>.
    Please note that several statistics require the demodulator to be fully
    locked (e. g. with FE_HAS_LOCK bit set). See
    <link linkend="frontend-stat-properties">Frontend statistics indicators</link>
    for more details.</para>
</section>

&sub-dvbproperty;

<section id="frontend_fcalls">
<title>Frontend Function Calls</title>

<refentry id="frontend_f_open">
  <refmeta>
    <refentrytitle>DVB frontend open()</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>fe-open</refname>
    <refpurpose>Open a frontend device</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;fcntl.h&gt;</funcsynopsisinfo>
      <funcprototype>
	<funcdef>int <function>open</function></funcdef>
	<paramdef>const char *<parameter>device_name</parameter></paramdef>
	<paramdef>int <parameter>flags</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>device_name</parameter></term>
	<listitem>
	  <para>Device to be opened.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>flags</parameter></term>
	<listitem>
	  <para>Open flags. Access can either be
              <constant>O_RDWR</constant> or <constant>O_RDONLY</constant>.</para>
          <para>Multiple opens are allowed with <constant>O_RDONLY</constant>. In this mode, only query and read ioctls are allowed.</para>
          <para>Only one open is allowed in <constant>O_RDWR</constant>. In this mode, all ioctls are allowed.</para>
	  <para>When the <constant>O_NONBLOCK</constant> flag is given, the system calls may return &EAGAIN; when no data is available or when the device driver is temporarily busy.</para>
         <para>Other flags have no effect.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
  <refsect1>
    <title>Description</title>
    <para>This system call opens a named frontend device (<constant>/dev/dvb/adapter?/frontend?</constant>)
 for subsequent use. Usually the first thing to do after a successful open is to
 find out the frontend type with <link linkend="FE_GET_INFO">FE_GET_INFO</link>.</para>
<para>The device can be opened in read-only mode, which only allows monitoring of
 device status and statistics, or read/write mode, which allows any kind of use
 (e.g. performing tuning operations.)
</para>
<para>In a system with multiple front-ends, it is usually the case that multiple devices
 cannot be open in read/write mode simultaneously. As long as a front-end
 device is opened in read/write mode, other open() calls in read/write mode will
 either fail or block, depending on whether non-blocking or blocking mode was
 specified. A front-end device opened in blocking mode can later be put into
 non-blocking mode (and vice versa) using the F_SETFL command of the fcntl
 system call. This is a standard system call, documented in the Linux manual
 page for fcntl. When an open() call has succeeded, the device will be ready
 for use in the specified mode. This implies that the corresponding hardware is
 powered up, and that other front-ends may have been powered down to make
 that possible.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success <function>open</function> returns the new file
descriptor. On error -1 is returned, and the <varname>errno</varname>
variable is set appropriately. Possible error codes are:</para>

    <variablelist>
      <varlistentry>
	<term><errorcode>EACCES</errorcode></term>
	<listitem>
	  <para>The caller has no permission to access the
device.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EBUSY</errorcode></term>
	<listitem>
	  <para>The the device driver is already in use.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENXIO</errorcode></term>
	<listitem>
	  <para>No device corresponding to this device special file
exists.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENOMEM</errorcode></term>
	<listitem>
	  <para>Not enough kernel memory was available to complete the
request.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EMFILE</errorcode></term>
	<listitem>
	  <para>The  process  already  has  the  maximum number of
files open.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENFILE</errorcode></term>
	<listitem>
	  <para>The limit on the total number of files open on the
system has been reached.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENODEV</errorcode></term>
	<listitem>
	  <para>The device got removed.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>

<refentry id="frontend_f_close">
  <refmeta>
    <refentrytitle>DVB frontend close()</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>fe-close</refname>
    <refpurpose>Close a frontend device</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;unistd.h&gt;</funcsynopsisinfo>
      <funcprototype>
	<funcdef>int <function>close</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>&fd;</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>
<para>This system call closes a previously opened front-end device. After closing
 a front-end device, its corresponding hardware might be powered down
 automatically.</para>
</refsect1>
  <refsect1>
    <title>Return Value</title>

    <para>The function returns <returnvalue>0</returnvalue> on
success, <returnvalue>-1</returnvalue> on failure and the
<varname>errno</varname> is set appropriately. Possible error
codes:</para>

    <variablelist>
      <varlistentry>
	<term><errorcode>EBADF</errorcode></term>
	<listitem>
	  <para><parameter>fd</parameter> is not a valid open file
descriptor.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>

&sub-fe-get-info;
&sub-fe-read-status;
&sub-fe-get-property;
&sub-fe-diseqc-reset-overload;
&sub-fe-diseqc-send-master-cmd;
&sub-fe-diseqc-recv-slave-reply;
&sub-fe-diseqc-send-burst;
&sub-fe-set-tone;
&sub-fe-set-voltage;
&sub-fe-enable-high-lnb-voltage;
&sub-fe-set-frontend-tune-mode;

</section>

<section id="frontend_legacy_dvbv3_api">
<title>DVB Frontend legacy API (a. k. a. DVBv3)</title>
<para>The usage of this API is deprecated, as it doesn't support all digital
    TV standards, doesn't provide good statistics measurements and provides
    incomplete information. This is kept only to support legacy applications.</para>

&sub-frontend_legacy_api;
</section>