1<refentry id="vidioc-querycap"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_QUERYCAP</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_QUERYCAP</refname> 9 <refpurpose>Query device capabilities</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct v4l2_capability *<parameter>argp</parameter></paramdef> 19 </funcprototype> 20 </funcsynopsis> 21 </refsynopsisdiv> 22 23 <refsect1> 24 <title>Arguments</title> 25 26 <variablelist> 27 <varlistentry> 28 <term><parameter>fd</parameter></term> 29 <listitem> 30 <para>&fd;</para> 31 </listitem> 32 </varlistentry> 33 <varlistentry> 34 <term><parameter>request</parameter></term> 35 <listitem> 36 <para>VIDIOC_QUERYCAP</para> 37 </listitem> 38 </varlistentry> 39 <varlistentry> 40 <term><parameter>argp</parameter></term> 41 <listitem> 42 <para></para> 43 </listitem> 44 </varlistentry> 45 </variablelist> 46 </refsect1> 47 48 <refsect1> 49 <title>Description</title> 50 51 <para>All V4L2 devices support the 52<constant>VIDIOC_QUERYCAP</constant> ioctl. It is used to identify 53kernel devices compatible with this specification and to obtain 54information about driver and hardware capabilities. The ioctl takes a 55pointer to a &v4l2-capability; which is filled by the driver. When the 56driver is not compatible with this specification the ioctl returns an 57&EINVAL;.</para> 58 59 <table pgwide="1" frame="none" id="v4l2-capability"> 60 <title>struct <structname>v4l2_capability</structname></title> 61 <tgroup cols="3"> 62 &cs-str; 63 <tbody valign="top"> 64 <row> 65 <entry>__u8</entry> 66 <entry><structfield>driver</structfield>[16]</entry> 67 <entry><para>Name of the driver, a unique NUL-terminated 68ASCII string. For example: "bttv". Driver specific applications can 69use this information to verify the driver identity. It is also useful 70to work around known bugs, or to identify drivers in error reports.</para> 71<para>Storing strings in fixed sized arrays is bad 72practice but unavoidable here. Drivers and applications should take 73precautions to never read or write beyond the end of the array and to 74make sure the strings are properly NUL-terminated.</para></entry> 75 </row> 76 <row> 77 <entry>__u8</entry> 78 <entry><structfield>card</structfield>[32]</entry> 79 <entry>Name of the device, a NUL-terminated ASCII string. 80For example: "Yoyodyne TV/FM". One driver may support different brands 81or models of video hardware. This information is intended for users, 82for example in a menu of available devices. Since multiple TV cards of 83the same brand may be installed which are supported by the same 84driver, this name should be combined with the character device file 85name (⪚ <filename>/dev/video2</filename>) or the 86<structfield>bus_info</structfield> string to avoid 87ambiguities.</entry> 88 </row> 89 <row> 90 <entry>__u8</entry> 91 <entry><structfield>bus_info</structfield>[32]</entry> 92 <entry>Location of the device in the system, a 93NUL-terminated ASCII string. For example: "PCI Slot 4". This 94information is intended for users, to distinguish multiple 95identical devices. If no such information is available the field may 96simply count the devices controlled by the driver, or contain the 97empty string (<structfield>bus_info</structfield>[0] = 0).<!-- XXX pci_dev->slot_name example --></entry> 98 </row> 99 <row> 100 <entry>__u32</entry> 101 <entry><structfield>version</structfield></entry> 102 <entry><para>Version number of the driver.</para> 103<para>Starting on kernel 3.1, the version reported is provided per 104V4L2 subsystem, following the same Kernel numberation scheme. However, it 105should not always return the same version as the kernel, if, for example, 106an stable or distribution-modified kernel uses the V4L2 stack from a 107newer kernel.</para> 108<para>The version number is formatted using the 109<constant>KERNEL_VERSION()</constant> macro:</para></entry> 110 </row> 111 <row> 112 <entry spanname="hspan"><para> 113<programlisting> 114#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c)) 115 116__u32 version = KERNEL_VERSION(0, 8, 1); 117 118printf ("Version: %u.%u.%u\n", 119 (version >> 16) & 0xFF, 120 (version >> 8) & 0xFF, 121 version & 0xFF); 122</programlisting></para></entry> 123 </row> 124 <row> 125 <entry>__u32</entry> 126 <entry><structfield>capabilities</structfield></entry> 127 <entry>Device capabilities, see <xref 128 linkend="device-capabilities" />.</entry> 129 </row> 130 <row> 131 <entry>__u32</entry> 132 <entry><structfield>reserved</structfield>[4]</entry> 133 <entry>Reserved for future extensions. Drivers must set 134this array to zero.</entry> 135 </row> 136 </tbody> 137 </tgroup> 138 </table> 139 140 <table pgwide="1" frame="none" id="device-capabilities"> 141 <title>Device Capabilities Flags</title> 142 <tgroup cols="3"> 143 &cs-def; 144 <tbody valign="top"> 145 <row> 146 <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry> 147 <entry>0x00000001</entry> 148 <entry>The device supports the single-planar API through the <link 149linkend="capture">Video Capture</link> interface.</entry> 150 </row> 151 <row> 152 <entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry> 153 <entry>0x00001000</entry> 154 <entry>The device supports the 155 <link linkend="planar-apis">multi-planar API</link> through the 156 <link linkend="capture">Video Capture</link> interface.</entry> 157 </row> 158 <row> 159 <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry> 160 <entry>0x00000002</entry> 161 <entry>The device supports the single-planar API through the <link 162linkend="output">Video Output</link> interface.</entry> 163 </row> 164 <row> 165 <entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry> 166 <entry>0x00002000</entry> 167 <entry>The device supports the 168 <link linkend="planar-apis">multi-planar API</link> through the 169 <link linkend="output">Video Output</link> interface.</entry> 170 </row> 171 <row> 172 <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry> 173 <entry>0x00000004</entry> 174 <entry>The device supports the <link 175linkend="overlay">Video Overlay</link> interface. A video overlay device 176typically stores captured images directly in the video memory of a 177graphics card, with hardware clipping and scaling.</entry> 178 </row> 179 <row> 180 <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry> 181 <entry>0x00000010</entry> 182 <entry>The device supports the <link linkend="raw-vbi">Raw 183VBI Capture</link> interface, providing Teletext and Closed Caption 184data.</entry> 185 </row> 186 <row> 187 <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry> 188 <entry>0x00000020</entry> 189 <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry> 190 </row> 191 <row> 192 <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry> 193 <entry>0x00000040</entry> 194 <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry> 195 </row> 196 <row> 197 <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry> 198 <entry>0x00000080</entry> 199 <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry> 200 </row> 201 <row> 202 <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry> 203 <entry>0x00000100</entry> 204 <entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry> 205 </row> 206 <row> 207 <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry> 208 <entry>0x00000200</entry> 209 <entry>The device supports the <link linkend="osd">Video 210Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video 211Overlay</wordasword> interface, this is a secondary function of video 212output devices and overlays an image onto an outgoing video signal. 213When the driver sets this flag, it must clear the 214<constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice 215versa.<footnote><para>The &v4l2-framebuffer; lacks an 216&v4l2-buf-type; field, therefore the type of overlay is implied by the 217driver capabilities.</para></footnote></entry> 218 </row> 219 <row> 220 <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry> 221 <entry>0x00000400</entry> 222 <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for 223hardware frequency seeking.</entry> 224 </row> 225 <row> 226 <entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry> 227 <entry>0x00000800</entry> 228 <entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry> 229 </row> 230 <row> 231 <entry><constant>V4L2_CAP_TUNER</constant></entry> 232 <entry>0x00010000</entry> 233 <entry>The device has some sort of tuner to 234receive RF-modulated video signals. For more information about 235tuner programming see 236<xref linkend="tuner" />.</entry> 237 </row> 238 <row> 239 <entry><constant>V4L2_CAP_AUDIO</constant></entry> 240 <entry>0x00020000</entry> 241 <entry>The device has audio inputs or outputs. It may or 242may not support audio recording or playback, in PCM or compressed 243formats. PCM audio support must be implemented as ALSA or OSS 244interface. For more information on audio inputs and outputs see <xref 245 linkend="audio" />.</entry> 246 </row> 247 <row> 248 <entry><constant>V4L2_CAP_RADIO</constant></entry> 249 <entry>0x00040000</entry> 250 <entry>This is a radio receiver.</entry> 251 </row> 252 <row> 253 <entry><constant>V4L2_CAP_MODULATOR</constant></entry> 254 <entry>0x00080000</entry> 255 <entry>The device has some sort of modulator to 256emit RF-modulated video/audio signals. For more information about 257modulator programming see 258<xref linkend="tuner" />.</entry> 259 </row> 260 <row> 261 <entry><constant>V4L2_CAP_READWRITE</constant></entry> 262 <entry>0x01000000</entry> 263 <entry>The device supports the <link 264linkend="rw">read()</link> and/or <link linkend="rw">write()</link> 265I/O methods.</entry> 266 </row> 267 <row> 268 <entry><constant>V4L2_CAP_ASYNCIO</constant></entry> 269 <entry>0x02000000</entry> 270 <entry>The device supports the <link 271linkend="async">asynchronous</link> I/O methods.</entry> 272 </row> 273 <row> 274 <entry><constant>V4L2_CAP_STREAMING</constant></entry> 275 <entry>0x04000000</entry> 276 <entry>The device supports the <link 277linkend="mmap">streaming</link> I/O method.</entry> 278 </row> 279 </tbody> 280 </tgroup> 281 </table> 282 </refsect1> 283 284 <refsect1> 285 &return-value; 286 </refsect1> 287</refentry> 288