<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="https://linuxtv.org/repo/">https://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>