Documentation/DocBook/v4l/vidioc-querycap.xml - maze/linux - Git at Google

 <refentry id="vidioc-querycap">
   <refmeta>
     <refentrytitle>ioctl VIDIOC_QUERYCAP</refentrytitle>
     &manvol;
   </refmeta>

   <refnamediv>
     <refname>VIDIOC_QUERYCAP</refname>
     <refpurpose>Query device capabilities</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_capability *<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_QUERYCAP</para>
 	</listitem>
       </varlistentry>
       <varlistentry>
 	<term><parameter>argp</parameter></term>
 	<listitem>
 	  <para></para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>

   <refsect1>
     <title>Description</title>

     <para>All V4L2 devices support the
 <constant>VIDIOC_QUERYCAP</constant> ioctl. It is used to identify
 kernel devices compatible with this specification and to obtain
 information about driver and hardware capabilities. The ioctl takes a
 pointer to a &v4l2-capability; which is filled by the driver. When the
 driver is not compatible with this specification the ioctl returns an
 &EINVAL;.</para>

     <table pgwide="1" frame="none" id="v4l2-capability">
       <title>struct <structname>v4l2_capability</structname></title>
       <tgroup cols="3">
 	&cs-str;
 	<tbody valign="top">
 	  <row>
 	    <entry>__u8</entry>
 	    <entry><structfield>driver</structfield>[16]</entry>
 	    <entry><para>Name of the driver, a unique NUL-terminated
 ASCII string. For example: "bttv". Driver specific applications can
 use this information to verify the driver identity. It is also useful
 to work around known bugs, or to identify drivers in error reports.
 The driver version is stored in the <structfield>version</structfield>
 field.</para><para>Storing strings in fixed sized arrays is bad
 practice but unavoidable here. Drivers and applications should take
 precautions to never read or write beyond the end of the array and to
 make sure the strings are properly NUL-terminated.</para></entry>
 	  </row>
 	  <row>
 	    <entry>__u8</entry>
 	    <entry><structfield>card</structfield>[32]</entry>
 	    <entry>Name of the device, a NUL-terminated ASCII string.
 For example: "Yoyodyne TV/FM". One driver may support different brands
 or models of video hardware. This information is intended for users,
 for example in a menu of available devices. Since multiple TV cards of
 the same brand may be installed which are supported by the same
 driver, this name should be combined with the character device file
 name (&eg; <filename>/dev/video2</filename>) or the
 <structfield>bus_info</structfield> string to avoid
 ambiguities.</entry>
 	  </row>
 	  <row>
 	    <entry>__u8</entry>
 	    <entry><structfield>bus_info</structfield>[32]</entry>
 	    <entry>Location of the device in the system, a
 NUL-terminated ASCII string. For example: "PCI Slot 4". This
 information is intended for users, to distinguish multiple
 identical devices. If no such information is available the field may
 simply count the devices controlled by the driver, or contain the
 empty string (<structfield>bus_info</structfield>[0] = 0).<!-- XXX pci_dev->slot_name example --></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>version</structfield></entry>
 	    <entry><para>Version number of the driver. Together with
 the <structfield>driver</structfield> field this identifies a
 particular driver. The version number is formatted using the
 <constant>KERNEL_VERSION()</constant> macro:</para></entry>
 	  </row>
 	  <row>
 	    <entry spanname="hspan"><para>
 <programlisting>
 #define KERNEL_VERSION(a,b,c) (((a) &lt;&lt; 16) + ((b) &lt;&lt; 8) + (c))

 __u32 version = KERNEL_VERSION(0, 8, 1);

 printf ("Version: %u.%u.%u\n",
 	(version &gt;&gt; 16) &amp; 0xFF,
 	(version &gt;&gt; 8) &amp; 0xFF,
 	 version &amp; 0xFF);
 </programlisting></para></entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>capabilities</structfield></entry>
 	    <entry>Device capabilities, see <xref
 		linkend="device-capabilities" />.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>reserved</structfield>[4]</entry>
 	    <entry>Reserved for future extensions. Drivers must set
 this array to zero.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="device-capabilities">
       <title>Device Capabilities Flags</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
 	    <entry>0x00000001</entry>
 	    <entry>The device supports the single-planar API through the <link
 linkend="capture">Video Capture</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry>
 	    <entry>0x00001000</entry>
 	    <entry>The device supports the
 	    <link linkend="planar-apis">multi-planar API</link> through the
 	    <link linkend="capture">Video Capture</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry>
 	    <entry>0x00000002</entry>
 	    <entry>The device supports the single-planar API through the <link
 linkend="output">Video Output</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry>
 	    <entry>0x00002000</entry>
 	    <entry>The device supports the
 	    <link linkend="planar-apis">multi-planar API</link> through the
 	    <link linkend="output">Video Output</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
 	    <entry>0x00000004</entry>
 	    <entry>The device supports the <link
 linkend="overlay">Video Overlay</link> interface. A video overlay device
 typically stores captured images directly in the video memory of a
 graphics card, with hardware clipping and scaling.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
 	    <entry>0x00000010</entry>
 	    <entry>The device supports the <link linkend="raw-vbi">Raw
 VBI Capture</link> interface, providing Teletext and Closed Caption
 data.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry>
 	    <entry>0x00000020</entry>
 	    <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry>
 	    <entry>0x00000040</entry>
 	    <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry>
 	    <entry>0x00000080</entry>
 	    <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry>
 	    <entry>0x00000100</entry>
 	    <entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry>
 	    <entry>0x00000200</entry>
 	    <entry>The device supports the <link linkend="osd">Video
 Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video
 Overlay</wordasword> interface, this is a secondary function of video
 output devices and overlays an image onto an outgoing video signal.
 When the driver sets this flag, it must clear the
 <constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice
 versa.<footnote><para>The &v4l2-framebuffer; lacks an
 &v4l2-buf-type; field, therefore the type of overlay is implied by the
 driver capabilities.</para></footnote></entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry>
 	    <entry>0x00000400</entry>
 	    <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for
 hardware frequency seeking.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry>
 	    <entry>0x00000800</entry>
 	    <entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_TUNER</constant></entry>
 	    <entry>0x00010000</entry>
 	    <entry>The device has some sort of tuner to
 receive RF-modulated video signals. For more information about
 tuner programming see
 <xref linkend="tuner" />.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_AUDIO</constant></entry>
 	    <entry>0x00020000</entry>
 	    <entry>The device has audio inputs or outputs. It may or
 may not support audio recording or playback, in PCM or compressed
 formats. PCM audio support must be implemented as ALSA or OSS
 interface. For more information on audio inputs and outputs see <xref
 		linkend="audio" />.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_RADIO</constant></entry>
 	    <entry>0x00040000</entry>
 	    <entry>This is a radio receiver.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_MODULATOR</constant></entry>
 	    <entry>0x00080000</entry>
 	    <entry>The device has some sort of modulator to
 emit RF-modulated video/audio signals. For more information about
 modulator programming see
 <xref linkend="tuner" />.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_READWRITE</constant></entry>
 	    <entry>0x01000000</entry>
 	    <entry>The device supports the <link
 linkend="rw">read()</link> and/or <link linkend="rw">write()</link>
 I/O methods.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_ASYNCIO</constant></entry>
 	    <entry>0x02000000</entry>
 	    <entry>The device supports the <link
 linkend="async">asynchronous</link> I/O methods.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_CAP_STREAMING</constant></entry>
 	    <entry>0x04000000</entry>
 	    <entry>The device supports the <link
 linkend="mmap">streaming</link> I/O method.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>
   </refsect1>

   <refsect1>
     &return-value;

     <variablelist>
       <varlistentry>
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The device is not compatible with this
 specification.</para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>

 <!--
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	<refentry id="vidioc-querycap">
	<refmeta>
	<refentrytitle>ioctl VIDIOC_QUERYCAP</refentrytitle>
	&manvol;
	</refmeta>

	<refnamediv>
	<refname>VIDIOC_QUERYCAP</refname>
	<refpurpose>Query device capabilities</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_capability *<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_QUERYCAP</para>
	</listitem>
	</varlistentry>
	<varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	<para></para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Description</title>

	<para>All V4L2 devices support the
	<constant>VIDIOC_QUERYCAP</constant> ioctl. It is used to identify
	kernel devices compatible with this specification and to obtain
	information about driver and hardware capabilities. The ioctl takes a
	pointer to a &v4l2-capability; which is filled by the driver. When the
	driver is not compatible with this specification the ioctl returns an
	&EINVAL;.</para>

	<table pgwide="1" frame="none" id="v4l2-capability">
	<title>struct <structname>v4l2_capability</structname></title>
	<tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	<row>
	<entry>__u8</entry>
	<entry><structfield>driver</structfield>[16]</entry>
	<entry><para>Name of the driver, a unique NUL-terminated
	ASCII string. For example: "bttv". Driver specific applications can
	use this information to verify the driver identity. It is also useful
	to work around known bugs, or to identify drivers in error reports.
	The driver version is stored in the <structfield>version</structfield>
	field.</para><para>Storing strings in fixed sized arrays is bad
	practice but unavoidable here. Drivers and applications should take
	precautions to never read or write beyond the end of the array and to
	make sure the strings are properly NUL-terminated.</para></entry>
	</row>
	<row>
	<entry>__u8</entry>
	<entry><structfield>card</structfield>[32]</entry>
	<entry>Name of the device, a NUL-terminated ASCII string.
	For example: "Yoyodyne TV/FM". One driver may support different brands
	or models of video hardware. This information is intended for users,
	for example in a menu of available devices. Since multiple TV cards of
	the same brand may be installed which are supported by the same
	driver, this name should be combined with the character device file
	name (&eg; <filename>/dev/video2</filename>) or the
	<structfield>bus_info</structfield> string to avoid
	ambiguities.</entry>
	</row>
	<row>
	<entry>__u8</entry>
	<entry><structfield>bus_info</structfield>[32]</entry>
	<entry>Location of the device in the system, a
	NUL-terminated ASCII string. For example: "PCI Slot 4". This
	information is intended for users, to distinguish multiple
	identical devices. If no such information is available the field may
	simply count the devices controlled by the driver, or contain the
	empty string (<structfield>bus_info</structfield>[0] = 0).<!-- XXX pci_dev->slot_name example --></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>version</structfield></entry>
	<entry><para>Version number of the driver. Together with
	the <structfield>driver</structfield> field this identifies a
	particular driver. The version number is formatted using the
	<constant>KERNEL_VERSION()</constant> macro:</para></entry>
	</row>
	<row>
	<entry spanname="hspan"><para>
	<programlisting>
	#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))

	__u32 version = KERNEL_VERSION(0, 8, 1);

	printf ("Version: %u.%u.%u\n",
	(version >> 16) & 0xFF,
	(version >> 8) & 0xFF,
	version & 0xFF);
	</programlisting></para></entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>capabilities</structfield></entry>
	<entry>Device capabilities, see <xref
	linkend="device-capabilities" />.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>reserved</structfield>[4]</entry>
	<entry>Reserved for future extensions. Drivers must set
	this array to zero.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="device-capabilities">
	<title>Device Capabilities Flags</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
	<entry>0x00000001</entry>
	<entry>The device supports the single-planar API through the <link
	linkend="capture">Video Capture</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry>
	<entry>0x00001000</entry>
	<entry>The device supports the
	<link linkend="planar-apis">multi-planar API</link> through the
	<link linkend="capture">Video Capture</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry>
	<entry>0x00000002</entry>
	<entry>The device supports the single-planar API through the <link
	linkend="output">Video Output</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry>
	<entry>0x00002000</entry>
	<entry>The device supports the
	<link linkend="planar-apis">multi-planar API</link> through the
	<link linkend="output">Video Output</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
	<entry>0x00000004</entry>
	<entry>The device supports the <link
	linkend="overlay">Video Overlay</link> interface. A video overlay device
	typically stores captured images directly in the video memory of a
	graphics card, with hardware clipping and scaling.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
	<entry>0x00000010</entry>
	<entry>The device supports the <link linkend="raw-vbi">Raw
	VBI Capture</link> interface, providing Teletext and Closed Caption
	data.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry>
	<entry>0x00000020</entry>
	<entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry>
	<entry>0x00000040</entry>
	<entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry>
	<entry>0x00000080</entry>
	<entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry>
	<entry>0x00000100</entry>
	<entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry>
	<entry>0x00000200</entry>
	<entry>The device supports the <link linkend="osd">Video
	Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video
	Overlay</wordasword> interface, this is a secondary function of video
	output devices and overlays an image onto an outgoing video signal.
	When the driver sets this flag, it must clear the
	<constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice
	versa.<footnote><para>The &v4l2-framebuffer; lacks an
	&v4l2-buf-type; field, therefore the type of overlay is implied by the
	driver capabilities.</para></footnote></entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry>
	<entry>0x00000400</entry>
	<entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for
	hardware frequency seeking.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry>
	<entry>0x00000800</entry>
	<entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_TUNER</constant></entry>
	<entry>0x00010000</entry>
	<entry>The device has some sort of tuner to
	receive RF-modulated video signals. For more information about
	tuner programming see
	<xref linkend="tuner" />.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_AUDIO</constant></entry>
	<entry>0x00020000</entry>
	<entry>The device has audio inputs or outputs. It may or
	may not support audio recording or playback, in PCM or compressed
	formats. PCM audio support must be implemented as ALSA or OSS
	interface. For more information on audio inputs and outputs see <xref
	linkend="audio" />.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_RADIO</constant></entry>
	<entry>0x00040000</entry>
	<entry>This is a radio receiver.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_MODULATOR</constant></entry>
	<entry>0x00080000</entry>
	<entry>The device has some sort of modulator to
	emit RF-modulated video/audio signals. For more information about
	modulator programming see
	<xref linkend="tuner" />.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_READWRITE</constant></entry>
	<entry>0x01000000</entry>
	<entry>The device supports the <link
	linkend="rw">read()</link> and/or <link linkend="rw">write()</link>
	I/O methods.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_ASYNCIO</constant></entry>
	<entry>0x02000000</entry>
	<entry>The device supports the <link
	linkend="async">asynchronous</link> I/O methods.</entry>
	</row>
	<row>
	<entry><constant>V4L2_CAP_STREAMING</constant></entry>
	<entry>0x04000000</entry>
	<entry>The device supports the <link
	linkend="mmap">streaming</link> I/O method.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>
	</refsect1>

	<refsect1>
	&return-value;

	<variablelist>
	<varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	<para>The device is not compatible with this
	specification.</para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>
	</refentry>

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