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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.</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 UTF-8 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:0000:05:06.0". This
+information is intended for users, to distinguish multiple
+identical devices. If no such information is available the field must
+simply count the devices controlled by the driver ("platform:vivi-000").
+The bus_info must start with "PCI:" for PCI boards, "PCIe:" for PCI Express boards,
+"usb-" for USB devices, "I2C:" for i2c devices, "ISA:" for ISA devices,
+"parport" for parallel port devices and "platform:" for platform devices.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>version</structfield></entry>
+ <entry><para>Version number of the driver.</para>
+<para>Starting on kernel 3.1, the version reported is provided per
+V4L2 subsystem, following the same Kernel numberation scheme. However, it
+should not always return the same version as the kernel, if, for example,
+an stable or distribution-modified kernel uses the V4L2 stack from a
+newer kernel.</para>
+<para>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>Available capabilities of the physical device as a whole, see <xref
+ linkend="device-capabilities" />. The same physical device can export
+ multiple devices in /dev (e.g. /dev/videoX, /dev/vbiY and /dev/radioZ).
+ The <structfield>capabilities</structfield> field should contain a union
+ of all capabilities available around the several V4L2 devices exported
+ to userspace.
+ For all those devices the <structfield>capabilities</structfield> field
+ returns the same set of capabilities. This allows applications to open
+ just one of the devices (typically the video device) and discover whether
+ video, vbi and/or radio are also supported.
+ </entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>device_caps</structfield></entry>
+ <entry>Device capabilities of the opened device, see <xref
+ linkend="device-capabilities" />. Should contain the available capabilities
+ of that specific device node. So, for example, <structfield>device_caps</structfield>
+ of a radio device will only contain radio related capabilities and
+ no video or vbi capabilities. This field is only set if the <structfield>capabilities</structfield>
+ field contains the <constant>V4L2_CAP_DEVICE_CAPS</constant> capability.
+ Only the <structfield>capabilities</structfield> field can have the
+ <constant>V4L2_CAP_DEVICE_CAPS</constant> capability, <structfield>device_caps</structfield>
+ will never set <constant>V4L2_CAP_DEVICE_CAPS</constant>.
+ </entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>reserved</structfield>[3]</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_M2M</constant></entry>
+ <entry>0x00004000</entry>
+ <entry>The device supports the single-planar API through the
+ Video Memory-To-Memory interface.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_CAP_VIDEO_M2M_MPLANE</constant></entry>
+ <entry>0x00008000</entry>
+ <entry>The device supports the
+ <link linkend="planar-apis">multi-planar API</link> through the
+ Video Memory-To-Memory 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>
+ <row>
+ <entry><constant>V4L2_CAP_DEVICE_CAPS</constant></entry>
+ <entry>0x80000000</entry>
+ <entry>The driver fills the <structfield>device_caps</structfield>
+ field. This capability can only appear in the <structfield>capabilities</structfield>
+ field and never in the <structfield>device_caps</structfield> field.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+ </refsect1>
+</refentry>