<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 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) << 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_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>