<refentry id="vidioc-dbg-g-chip-ident">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_DBG_G_CHIP_IDENT</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_DBG_G_CHIP_IDENT</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_ident
*<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_IDENT</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>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-ident;
and call <constant>VIDIOC_DBG_G_CHIP_IDENT</constant> with a pointer to
this structure. On success the driver stores information about the
selected chip in the <structfield>ident</structfield> and
<structfield>revision</structfield> fields. On failure the structure
remains unchanged.</para>

    <para>When <structfield>match.type</structfield> is
<constant>V4L2_CHIP_MATCH_HOST</constant>,
<structfield>match.addr</structfield> selects the nth non-&i2c; 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_IDENT</constant> fails with an &EINVAL;.
The number zero always selects the host chip, &eg; the chip connected
to the PCI or USB bus.</para>

    <para>When <structfield>match.type</structfield> is
<constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant>,
<structfield>match.name</structfield> contains the I2C driver name.
For instance
<constant>"saa7127"</constant> will match any chip
supported by the saa7127 driver, regardless of its &i2c; bus address.
When multiple chips supported by the same driver are present, the
ioctl will return <constant>V4L2_IDENT_AMBIGUOUS</constant> in the
<structfield>ident</structfield> field.</para>

    <para>When <structfield>match.type</structfield> is
<constant>V4L2_CHIP_MATCH_I2C_ADDR</constant>,
<structfield>match.addr</structfield> selects a chip by its 7 bit
&i2c; bus address.</para>

    <para>When <structfield>match.type</structfield> is
<constant>V4L2_CHIP_MATCH_AC97</constant>,
<structfield>match.addr</structfield> selects the nth AC97 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_IDENT</constant> fails with an &EINVAL;.</para>

    <para>On success, the <structfield>ident</structfield> field will
contain a chip ID from the Linux
<filename>media/v4l2-chip-ident.h</filename> header file, and the
<structfield>revision</structfield> field will contain a driver
specific value, or zero if no particular revision is associated with
this chip.</para>

    <para>When the driver could not identify the selected chip,
<structfield>ident</structfield> will contain
<constant>V4L2_IDENT_UNKNOWN</constant>. When no chip matched
the ioctl will succeed but the
<structfield>ident</structfield> field will contain
<constant>V4L2_IDENT_NONE</constant>. If multiple chips matched,
<structfield>ident</structfield> will contain
<constant>V4L2_IDENT_AMBIGUOUS</constant>. In all these cases the
<structfield>revision</structfield> field remains unchanged.</para>

    <para>This ioctl is optional, not all drivers may support it. It
was introduced in Linux 2.6.21, but the API was changed to the
one described here in 2.6.29.</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="ident-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="ident-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.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="v4l2-dbg-chip-ident">
      <title>struct <structname>v4l2_dbg_chip_ident</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="ident-v4l2-dbg-match" />.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>ident</structfield></entry>
	    <entry>A chip identifier as defined in the Linux
<filename>media/v4l2-chip-ident.h</filename> header file, or one of
the values from <xref linkend="chip-ids" />.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>revision</structfield></entry>
	    <entry>A chip revision, chip and driver specific.</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="ident-chip-match-types">
      <title>Chip Match Types</title>
      <tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_CHIP_MATCH_HOST</constant></entry>
	    <entry>0</entry>
	    <entry>Match the nth chip on the card, zero for the
	    host chip. Does not match &i2c; chips.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant></entry>
	    <entry>1</entry>
	    <entry>Match an &i2c; chip by its driver name.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_CHIP_MATCH_I2C_ADDR</constant></entry>
	    <entry>2</entry>
	    <entry>Match a chip by its 7 bit &i2c; bus address.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_CHIP_MATCH_AC97</constant></entry>
	    <entry>3</entry>
	    <entry>Match the nth anciliary AC97 chip.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <!-- This is an anonymous enum in media/v4l2-chip-ident.h. -->
    <table pgwide="1" frame="none" id="chip-ids">
      <title>Chip Identifiers</title>
      <tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_IDENT_NONE</constant></entry>
	    <entry>0</entry>
	    <entry>No chip matched.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_IDENT_AMBIGUOUS</constant></entry>
	    <entry>1</entry>
	    <entry>Multiple chips matched.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_IDENT_UNKNOWN</constant></entry>
	    <entry>2</entry>
	    <entry>A chip is present at this address, but the driver
could not identify it.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The driver does not support this ioctl, or the
<structfield>match_type</structfield> is invalid.</para>
	</listitem>
      </varlistentry>
     </variablelist>
  </refsect1>
</refentry>

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