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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 (⪚ <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 with kernel 3.1, the version reported is provided by the
- V4L2 subsystem following the kernel numbering scheme. However, it
- may not always return the same version as the kernel if, for example,
- a 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) << 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>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_SDR_CAPTURE</constant></entry>
- <entry>0x00100000</entry>
- <entry>The device supports the
- <link linkend="sdr">SDR Capture</link> interface.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CAP_EXT_PIX_FORMAT</constant></entry>
- <entry>0x00200000</entry>
- <entry>The device supports the &v4l2-pix-format; extended
- fields.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CAP_SDR_OUTPUT</constant></entry>
- <entry>0x00400000</entry>
- <entry>The device supports the
- <link linkend="sdr">SDR Output</link> interface.</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>
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