Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
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 53 kernel devices compatible with this specification and to obtain 54 information about driver and hardware capabilities. The ioctl takes a 55 pointer to a &v4l2-capability; which is filled by the driver. When the 56 driver 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 68 ASCII string. For example: "bttv". Driver specific applications can 69 use this information to verify the driver identity. It is also useful 70 to work around known bugs, or to identify drivers in error reports. 71 The driver version is stored in the <structfield>version</structfield> 72 field.</para><para>Storing strings in fixed sized arrays is bad 73 practice but unavoidable here. Drivers and applications should take 74 precautions to never read or write beyond the end of the array and to 75 make sure the strings are properly NUL-terminated.</para></entry> 76 </row> 77 <row> 78 <entry>__u8</entry> 79 <entry><structfield>card</structfield>[32]</entry> 80 <entry>Name of the device, a NUL-terminated ASCII string. 81 For example: "Yoyodyne TV/FM". One driver may support different brands 82 or models of video hardware. This information is intended for users, 83 for example in a menu of available devices. Since multiple TV cards of 84 the same brand may be installed which are supported by the same 85 driver, this name should be combined with the character device file 86 name (⪚ <filename>/dev/video2</filename>) or the 87 <structfield>bus_info</structfield> string to avoid 88 ambiguities.</entry> 89 </row> 90 <row> 91 <entry>__u8</entry> 92 <entry><structfield>bus_info</structfield>[32]</entry> 93 <entry>Location of the device in the system, a 94 NUL-terminated ASCII string. For example: "PCI Slot 4". This 95 information is intended for users, to distinguish multiple 96 identical devices. If no such information is available the field may 97 simply count the devices controlled by the driver, or contain the 98 empty string (<structfield>bus_info</structfield>[0] = 0).<!-- XXX pci_dev->slot_name example --></entry> 99 </row> 100 <row> 101 <entry>__u32</entry> 102 <entry><structfield>version</structfield></entry> 103 <entry><para>Version number of the driver. Together with 104 the <structfield>driver</structfield> field this identifies a 105 particular driver. The version number is formatted using the 106 <constant>KERNEL_VERSION()</constant> macro:</para></entry> 107 </row> 108 <row> 109 <entry spanname="hspan"><para> 110 <programlisting> 111 #define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c)) 112 113 __u32 version = KERNEL_VERSION(0, 8, 1); 114 115 printf ("Version: %u.%u.%u\n", 116 (version >> 16) & 0xFF, 117 (version >> 8) & 0xFF, 118 version & 0xFF); 119 </programlisting></para></entry> 120 </row> 121 <row> 122 <entry>__u32</entry> 123 <entry><structfield>capabilities</structfield></entry> 124 <entry>Device capabilities, see <xref 125 linkend="device-capabilities" />.</entry> 126 </row> 127 <row> 128 <entry>__u32</entry> 129 <entry><structfield>reserved</structfield>[4]</entry> 130 <entry>Reserved for future extensions. Drivers must set 131 this array to zero.</entry> 132 </row> 133 </tbody> 134 </tgroup> 135 </table> 136 137 <table pgwide="1" frame="none" id="device-capabilities"> 138 <title>Device Capabilities Flags</title> 139 <tgroup cols="3"> 140 &cs-def; 141 <tbody valign="top"> 142 <row> 143 <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry> 144 <entry>0x00000001</entry> 145 <entry>The device supports the single-planar API through the <link 146 linkend="capture">Video Capture</link> interface.</entry> 147 </row> 148 <row> 149 <entry><constant>V4L2_CAP_VIDEO_CAPTURE_MPLANE</constant></entry> 150 <entry>0x00001000</entry> 151 <entry>The device supports the 152 <link linkend="planar-apis">multi-planar API</link> through the 153 <link linkend="capture">Video Capture</link> interface.</entry> 154 </row> 155 <row> 156 <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry> 157 <entry>0x00000002</entry> 158 <entry>The device supports the single-planar API through the <link 159 linkend="output">Video Output</link> interface.</entry> 160 </row> 161 <row> 162 <entry><constant>V4L2_CAP_VIDEO_OUTPUT_MPLANE</constant></entry> 163 <entry>0x00002000</entry> 164 <entry>The device supports the 165 <link linkend="planar-apis">multi-planar API</link> through the 166 <link linkend="output">Video Output</link> interface.</entry> 167 </row> 168 <row> 169 <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry> 170 <entry>0x00000004</entry> 171 <entry>The device supports the <link 172 linkend="overlay">Video Overlay</link> interface. A video overlay device 173 typically stores captured images directly in the video memory of a 174 graphics card, with hardware clipping and scaling.</entry> 175 </row> 176 <row> 177 <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry> 178 <entry>0x00000010</entry> 179 <entry>The device supports the <link linkend="raw-vbi">Raw 180 VBI Capture</link> interface, providing Teletext and Closed Caption 181 data.</entry> 182 </row> 183 <row> 184 <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry> 185 <entry>0x00000020</entry> 186 <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry> 187 </row> 188 <row> 189 <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry> 190 <entry>0x00000040</entry> 191 <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry> 192 </row> 193 <row> 194 <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry> 195 <entry>0x00000080</entry> 196 <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry> 197 </row> 198 <row> 199 <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry> 200 <entry>0x00000100</entry> 201 <entry>The device supports the <link linkend="rds">RDS</link> capture interface.</entry> 202 </row> 203 <row> 204 <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry> 205 <entry>0x00000200</entry> 206 <entry>The device supports the <link linkend="osd">Video 207 Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video 208 Overlay</wordasword> interface, this is a secondary function of video 209 output devices and overlays an image onto an outgoing video signal. 210 When the driver sets this flag, it must clear the 211 <constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice 212 versa.<footnote><para>The &v4l2-framebuffer; lacks an 213 &v4l2-buf-type; field, therefore the type of overlay is implied by the 214 driver capabilities.</para></footnote></entry> 215 </row> 216 <row> 217 <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry> 218 <entry>0x00000400</entry> 219 <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for 220 hardware frequency seeking.</entry> 221 </row> 222 <row> 223 <entry><constant>V4L2_CAP_RDS_OUTPUT</constant></entry> 224 <entry>0x00000800</entry> 225 <entry>The device supports the <link linkend="rds">RDS</link> output interface.</entry> 226 </row> 227 <row> 228 <entry><constant>V4L2_CAP_TUNER</constant></entry> 229 <entry>0x00010000</entry> 230 <entry>The device has some sort of tuner to 231 receive RF-modulated video signals. For more information about 232 tuner programming see 233 <xref linkend="tuner" />.</entry> 234 </row> 235 <row> 236 <entry><constant>V4L2_CAP_AUDIO</constant></entry> 237 <entry>0x00020000</entry> 238 <entry>The device has audio inputs or outputs. It may or 239 may not support audio recording or playback, in PCM or compressed 240 formats. PCM audio support must be implemented as ALSA or OSS 241 interface. For more information on audio inputs and outputs see <xref 242 linkend="audio" />.</entry> 243 </row> 244 <row> 245 <entry><constant>V4L2_CAP_RADIO</constant></entry> 246 <entry>0x00040000</entry> 247 <entry>This is a radio receiver.</entry> 248 </row> 249 <row> 250 <entry><constant>V4L2_CAP_MODULATOR</constant></entry> 251 <entry>0x00080000</entry> 252 <entry>The device has some sort of modulator to 253 emit RF-modulated video/audio signals. For more information about 254 modulator programming see 255 <xref linkend="tuner" />.</entry> 256 </row> 257 <row> 258 <entry><constant>V4L2_CAP_READWRITE</constant></entry> 259 <entry>0x01000000</entry> 260 <entry>The device supports the <link 261 linkend="rw">read()</link> and/or <link linkend="rw">write()</link> 262 I/O methods.</entry> 263 </row> 264 <row> 265 <entry><constant>V4L2_CAP_ASYNCIO</constant></entry> 266 <entry>0x02000000</entry> 267 <entry>The device supports the <link 268 linkend="async">asynchronous</link> I/O methods.</entry> 269 </row> 270 <row> 271 <entry><constant>V4L2_CAP_STREAMING</constant></entry> 272 <entry>0x04000000</entry> 273 <entry>The device supports the <link 274 linkend="mmap">streaming</link> I/O method.</entry> 275 </row> 276 </tbody> 277 </tgroup> 278 </table> 279 </refsect1> 280 281 <refsect1> 282 &return-value; 283 284 <variablelist> 285 <varlistentry> 286 <term><errorcode>EINVAL</errorcode></term> 287 <listitem> 288 <para>The device is not compatible with this 289 specification.</para> 290 </listitem> 291 </varlistentry> 292 </variablelist> 293 </refsect1> 294 </refentry> 295 296 <!-- 297 Local Variables: 298 mode: sgml 299 sgml-parent-document: "v4l2.sgml" 300 indent-tabs-mode: nil 301 End: 302 -->
