diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-querycap.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-querycap.xml | 317 |
1 files changed, 317 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-querycap.xml b/Documentation/DocBook/media/v4l/vidioc-querycap.xml new file mode 100644 index 00000000..4643505c --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-querycap.xml @@ -0,0 +1,317 @@ +<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 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.</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_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> |