| <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 (⪚ <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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