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. 71The driver version is stored in the <structfield>version</structfield> 72field.</para><para>Storing strings in fixed sized arrays is bad 73practice but unavoidable here. Drivers and applications should take 74precautions to never read or write beyond the end of the array and to 75make 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. 81For example: "Yoyodyne TV/FM". One driver may support different brands 82or models of video hardware. This information is intended for users, 83for example in a menu of available devices. Since multiple TV cards of 84the same brand may be installed which are supported by the same 85driver, this name should be combined with the character device file 86name (⪚ <filename>/dev/video2</filename>) or the 87<structfield>bus_info</structfield> string to avoid 88ambiguities.</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 94NUL-terminated ASCII string. For example: "PCI Slot 4". This 95information is intended for users, to distinguish multiple 96identical devices. If no such information is available the field may 97simply count the devices controlled by the driver, or contain the 98empty 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 104the <structfield>driver</structfield> field this identifies a 105particular 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 115printf ("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 131this 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 <link 146linkend="capture">Video Capture</link> interface.</entry> 147 </row> 148 <row> 149 <entry><constant>V4L2_CAP_VIDEO_OUTPUT</constant></entry> 150 <entry>0x00000002</entry> 151 <entry>The device supports the <link 152linkend="output">Video Output</link> interface.</entry> 153 </row> 154 <row> 155 <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry> 156 <entry>0x00000004</entry> 157 <entry>The device supports the <link 158linkend="overlay">Video Overlay</link> interface. A video overlay device 159typically stores captured images directly in the video memory of a 160graphics card, with hardware clipping and scaling.</entry> 161 </row> 162 <row> 163 <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry> 164 <entry>0x00000010</entry> 165 <entry>The device supports the <link linkend="raw-vbi">Raw 166VBI Capture</link> interface, providing Teletext and Closed Caption 167data.</entry> 168 </row> 169 <row> 170 <entry><constant>V4L2_CAP_VBI_OUTPUT</constant></entry> 171 <entry>0x00000020</entry> 172 <entry>The device supports the <link linkend="raw-vbi">Raw VBI Output</link> interface.</entry> 173 </row> 174 <row> 175 <entry><constant>V4L2_CAP_SLICED_VBI_CAPTURE</constant></entry> 176 <entry>0x00000040</entry> 177 <entry>The device supports the <link linkend="sliced">Sliced VBI Capture</link> interface.</entry> 178 </row> 179 <row> 180 <entry><constant>V4L2_CAP_SLICED_VBI_OUTPUT</constant></entry> 181 <entry>0x00000080</entry> 182 <entry>The device supports the <link linkend="sliced">Sliced VBI Output</link> interface.</entry> 183 </row> 184 <row> 185 <entry><constant>V4L2_CAP_RDS_CAPTURE</constant></entry> 186 <entry>0x00000100</entry> 187 <entry>The device supports the <link linkend="rds">RDS</link> interface.</entry> 188 </row> 189 <row> 190 <entry><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant></entry> 191 <entry>0x00000200</entry> 192 <entry>The device supports the <link linkend="osd">Video 193Output Overlay</link> (OSD) interface. Unlike the <wordasword>Video 194Overlay</wordasword> interface, this is a secondary function of video 195output devices and overlays an image onto an outgoing video signal. 196When the driver sets this flag, it must clear the 197<constant>V4L2_CAP_VIDEO_OVERLAY</constant> flag and vice 198versa.<footnote><para>The &v4l2-framebuffer; lacks an 199&v4l2-buf-type; field, therefore the type of overlay is implied by the 200driver capabilities.</para></footnote></entry> 201 </row> 202 <row> 203 <entry><constant>V4L2_CAP_HW_FREQ_SEEK</constant></entry> 204 <entry>0x00000400</entry> 205 <entry>The device supports the &VIDIOC-S-HW-FREQ-SEEK; ioctl for 206hardware frequency seeking.</entry> 207 </row> 208 <row> 209 <entry><constant>V4L2_CAP_TUNER</constant></entry> 210 <entry>0x00010000</entry> 211 <entry>The device has some sort of tuner to 212receive RF-modulated video signals. For more information about 213tuner programming see 214<xref linkend="tuner" />.</entry> 215 </row> 216 <row> 217 <entry><constant>V4L2_CAP_AUDIO</constant></entry> 218 <entry>0x00020000</entry> 219 <entry>The device has audio inputs or outputs. It may or 220may not support audio recording or playback, in PCM or compressed 221formats. PCM audio support must be implemented as ALSA or OSS 222interface. For more information on audio inputs and outputs see <xref 223 linkend="audio" />.</entry> 224 </row> 225 <row> 226 <entry><constant>V4L2_CAP_RADIO</constant></entry> 227 <entry>0x00040000</entry> 228 <entry>This is a radio receiver.</entry> 229 </row> 230 <row> 231 <entry><constant>V4L2_CAP_MODULATOR</constant></entry> 232 <entry>0x00080000</entry> 233 <entry>The device has some sort of modulator to 234emit RF-modulated video/audio signals. For more information about 235modulator programming see 236<xref linkend="tuner" />.</entry> 237 </row> 238 <row> 239 <entry><constant>V4L2_CAP_READWRITE</constant></entry> 240 <entry>0x01000000</entry> 241 <entry>The device supports the <link 242linkend="rw">read()</link> and/or <link linkend="rw">write()</link> 243I/O methods.</entry> 244 </row> 245 <row> 246 <entry><constant>V4L2_CAP_ASYNCIO</constant></entry> 247 <entry>0x02000000</entry> 248 <entry>The device supports the <link 249linkend="async">asynchronous</link> I/O methods.</entry> 250 </row> 251 <row> 252 <entry><constant>V4L2_CAP_STREAMING</constant></entry> 253 <entry>0x04000000</entry> 254 <entry>The device supports the <link 255linkend="mmap">streaming</link> I/O method.</entry> 256 </row> 257 </tbody> 258 </tgroup> 259 </table> 260 </refsect1> 261 262 <refsect1> 263 &return-value; 264 265 <variablelist> 266 <varlistentry> 267 <term><errorcode>EINVAL</errorcode></term> 268 <listitem> 269 <para>The device is not compatible with this 270specification.</para> 271 </listitem> 272 </varlistentry> 273 </variablelist> 274 </refsect1> 275</refentry> 276 277<!-- 278Local Variables: 279mode: sgml 280sgml-parent-document: "v4l2.sgml" 281indent-tabs-mode: nil 282End: 283--> 284 285