<refentry id="vidioc-dbg-g-chip-info">
    <refmeta>
      <refentrytitle>ioctl VIDIOC_DBG_G_CHIP_INFO</refentrytitle>
      &manvol;
    </refmeta>
  
    <refnamediv>
      <refname>VIDIOC_DBG_G_CHIP_INFO</refname>
      <refpurpose>Identify the chips on a TV card</refpurpose>
    </refnamediv>
  
    <refsynopsisdiv>
      <funcsynopsis>
        <funcprototype>
  	<funcdef>int <function>ioctl</function></funcdef>
  	<paramdef>int <parameter>fd</parameter></paramdef>
  	<paramdef>int <parameter>request</parameter></paramdef>
  	<paramdef>struct v4l2_dbg_chip_info
  *<parameter>argp</parameter></paramdef>
        </funcprototype>
      </funcsynopsis>
    </refsynopsisdiv>
  
    <refsect1>
      <title>Arguments</title>
  
      <variablelist>
        <varlistentry>
  	<term><parameter>fd</parameter></term>
  	<listitem>
  	  <para>&fd;</para>
  	</listitem>
        </varlistentry>
        <varlistentry>
  	<term><parameter>request</parameter></term>
  	<listitem>
  	  <para>VIDIOC_DBG_G_CHIP_INFO</para>
  	</listitem>
        </varlistentry>
        <varlistentry>
  	<term><parameter>argp</parameter></term>
  	<listitem>
  	  <para></para>
  	</listitem>
        </varlistentry>
      </variablelist>
    </refsect1>
  
    <refsect1>
      <title>Description</title>
  
      <note>
        <title>Experimental</title>
  
        <para>This is an <link
  linkend="experimental">experimental</link> interface and may change in
  the future.</para>
      </note>
  
      <para>For driver debugging purposes this ioctl allows test
  applications to query the driver about the chips present on the TV
  card. Regular applications must not use it. When you found a chip
  specific bug, please contact the linux-media mailing list (&v4l-ml;)
  so it can be fixed.</para>
  
      <para>Additionally the Linux kernel must be compiled with the
  <constant>CONFIG_VIDEO_ADV_DEBUG</constant> option to enable this ioctl.</para>
  
      <para>To query the driver applications must initialize the
  <structfield>match.type</structfield> and
  <structfield>match.addr</structfield> or <structfield>match.name</structfield>
  fields of a &v4l2-dbg-chip-info;
  and call <constant>VIDIOC_DBG_G_CHIP_INFO</constant> with a pointer to
  this structure. On success the driver stores information about the
  selected chip in the <structfield>name</structfield> and
  <structfield>flags</structfield> fields.</para>
  
      <para>When <structfield>match.type</structfield> is
  <constant>V4L2_CHIP_MATCH_BRIDGE</constant>,
  <structfield>match.addr</structfield> selects the nth bridge 'chip'
  on the TV card. You can enumerate all chips by starting at zero and
  incrementing <structfield>match.addr</structfield> by one until
  <constant>VIDIOC_DBG_G_CHIP_INFO</constant> fails with an &EINVAL;.
  The number zero always selects the bridge chip itself, &eg; the chip
  connected to the PCI or USB bus. Non-zero numbers identify specific
  parts of the bridge chip such as an AC97 register block.</para>
  
      <para>When <structfield>match.type</structfield> is
  <constant>V4L2_CHIP_MATCH_SUBDEV</constant>,
  <structfield>match.addr</structfield> selects the nth sub-device. This
  allows you to enumerate over all sub-devices.</para>
  
      <para>On success, the <structfield>name</structfield> field will
  contain a chip name and the <structfield>flags</structfield> field will
  contain <constant>V4L2_CHIP_FL_READABLE</constant> if the driver supports
  reading registers from the device or <constant>V4L2_CHIP_FL_WRITABLE</constant>
  if the driver supports writing registers to the device.</para>
  
      <para>We recommended the <application>v4l2-dbg</application>
  utility over calling this ioctl directly. It is available from the
  LinuxTV v4l-dvb repository; see <ulink
  url="http://linuxtv.org/repo/">http://linuxtv.org/repo/</ulink> for
  access instructions.</para>
  
      <!-- Note for convenience vidioc-dbg-g-register.sgml
  	 contains a duplicate of this table. -->
      <table pgwide="1" frame="none" id="name-v4l2-dbg-match">
        <title>struct <structname>v4l2_dbg_match</structname></title>
        <tgroup cols="4">
  	&cs-ustr;
  	<tbody valign="top">
  	  <row>
  	    <entry>__u32</entry>
  	    <entry><structfield>type</structfield></entry>
  	    <entry>See <xref linkend="name-chip-match-types" /> for a list of
  possible types.</entry>
  	  </row>
  	  <row>
  	    <entry>union</entry>
  	    <entry>(anonymous)</entry>
  	  </row>
  	  <row>
  	    <entry></entry>
  	    <entry>__u32</entry>
  	    <entry><structfield>addr</structfield></entry>
  	    <entry>Match a chip by this number, interpreted according
  to the <structfield>type</structfield> field.</entry>
  	  </row>
  	  <row>
  	    <entry></entry>
  	    <entry>char</entry>
  	    <entry><structfield>name[32]</structfield></entry>
  	    <entry>Match a chip by this name, interpreted according
  to the <structfield>type</structfield> field. Currently unused.</entry>
  	  </row>
  	</tbody>
        </tgroup>
      </table>
  
      <table pgwide="1" frame="none" id="v4l2-dbg-chip-info">
        <title>struct <structname>v4l2_dbg_chip_info</structname></title>
        <tgroup cols="3">
  	&cs-str;
  	<tbody valign="top">
  	  <row>
  	    <entry>struct v4l2_dbg_match</entry>
  	    <entry><structfield>match</structfield></entry>
  	    <entry>How to match the chip, see <xref linkend="name-v4l2-dbg-match" />.</entry>
  	  </row>
  	  <row>
  	    <entry>char</entry>
  	    <entry><structfield>name[32]</structfield></entry>
  	    <entry>The name of the chip.</entry>
  	  </row>
  	  <row>
  	    <entry>__u32</entry>
  	    <entry><structfield>flags</structfield></entry>
  	    <entry>Set by the driver. If <constant>V4L2_CHIP_FL_READABLE</constant>
  is set, then the driver supports reading registers from the device. If
  <constant>V4L2_CHIP_FL_WRITABLE</constant> is set, then it supports writing registers.</entry>
  	  </row>
  	  <row>
  	    <entry>__u32</entry>
  	    <entry><structfield>reserved[8]</structfield></entry>
  	    <entry>Reserved fields, both application and driver must set these to 0.</entry>
  	  </row>
  	</tbody>
        </tgroup>
      </table>
  
      <!-- Note for convenience vidioc-dbg-g-register.sgml
  	 contains a duplicate of this table. -->
      <table pgwide="1" frame="none" id="name-chip-match-types">
        <title>Chip Match Types</title>
        <tgroup cols="3">
  	&cs-def;
  	<tbody valign="top">
  	  <row>
  	    <entry><constant>V4L2_CHIP_MATCH_BRIDGE</constant></entry>
  	    <entry>0</entry>
  	    <entry>Match the nth chip on the card, zero for the
  	    bridge chip. Does not match sub-devices.</entry>
  	  </row>
  	  <row>
  	    <entry><constant>V4L2_CHIP_MATCH_SUBDEV</constant></entry>
  	    <entry>4</entry>
  	    <entry>Match the nth sub-device.</entry>
  	  </row>
  	</tbody>
        </tgroup>
      </table>
    </refsect1>
  
    <refsect1>
      &return-value;
  
      <variablelist>
        <varlistentry>
  	<term><errorcode>EINVAL</errorcode></term>
  	<listitem>
  	  <para>The <structfield>match_type</structfield> is invalid or
  no device could be matched.</para>
  	</listitem>
        </varlistentry>
       </variablelist>
    </refsect1>
  </refentry>