285 lines
9.6 KiB
XML
285 lines
9.6 KiB
XML
<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 <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 <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> 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_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>
|
|
|
|
<!--
|
|
Local Variables:
|
|
mode: sgml
|
|
sgml-parent-document: "v4l2.sgml"
|
|
indent-tabs-mode: nil
|
|
End:
|
|
-->
|
|
|