1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> 2 <HTML 3 ><HEAD 4 ><TITLE 5 >V4L2 ioctl()</TITLE 6 ><META 7 NAME="GENERATOR" 8 CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK 9 REL="HOME" 10 TITLE="Video for Linux Two API Specification" 11 HREF="book1.htm"><LINK 12 REL="UP" 13 TITLE="Function Reference" 14 HREF="r7624.htm"><LINK 15 REL="PREVIOUS" 16 TITLE="V4L2 close()" 17 HREF="r7626.htm"><LINK 18 REL="NEXT" 19 TITLE="ioctl VIDIOC_CROPCAP" 20 HREF="r7771.htm"></HEAD 21 ><BODY 22 CLASS="REFENTRY" 23 BGCOLOR="#FFFFFF" 24 TEXT="#000000" 25 LINK="#0000FF" 26 VLINK="#840084" 27 ALINK="#0000FF" 28 ><DIV 29 CLASS="NAVHEADER" 30 ><TABLE 31 SUMMARY="Header navigation table" 32 WIDTH="100%" 33 BORDER="0" 34 CELLPADDING="0" 35 CELLSPACING="0" 36 ><TR 37 ><TH 38 COLSPAN="3" 39 ALIGN="center" 40 >Video for Linux Two API Specification: Revision 0.24</TH 41 ></TR 42 ><TR 43 ><TD 44 WIDTH="10%" 45 ALIGN="left" 46 VALIGN="bottom" 47 ><A 48 HREF="r7626.htm" 49 ACCESSKEY="P" 50 >Prev</A 51 ></TD 52 ><TD 53 WIDTH="80%" 54 ALIGN="center" 55 VALIGN="bottom" 56 ></TD 57 ><TD 58 WIDTH="10%" 59 ALIGN="right" 60 VALIGN="bottom" 61 ><A 62 HREF="r7771.htm" 63 ACCESSKEY="N" 64 >Next</A 65 ></TD 66 ></TR 67 ></TABLE 68 ><HR 69 ALIGN="LEFT" 70 WIDTH="100%"></DIV 71 ><H1 72 ><A 73 NAME="FUNC-IOCTL" 74 ></A 75 >V4L2 ioctl()</H1 76 ><DIV 77 CLASS="REFNAMEDIV" 78 ><A 79 NAME="AEN7671" 80 ></A 81 ><H2 82 >Name</H2 83 >v4l2-ioctl -- Program a V4L2 device</DIV 84 ><DIV 85 CLASS="REFSYNOPSISDIV" 86 ><A 87 NAME="AEN7674" 88 ></A 89 ><H2 90 >Synopsis</H2 91 ><DIV 92 CLASS="FUNCSYNOPSIS" 93 ><P 94 ></P 95 ><A 96 NAME="AEN7675" 97 ></A 98 ><PRE 99 CLASS="FUNCSYNOPSISINFO" 100 >#include <sys/ioctl.h></PRE 101 ><P 102 ><CODE 103 ><CODE 104 CLASS="FUNCDEF" 105 >int ioctl</CODE 106 >(int fd, int request, void *argp);</CODE 107 ></P 108 ><P 109 ></P 110 ></DIV 111 ></DIV 112 ><DIV 113 CLASS="REFSECT1" 114 ><A 115 NAME="AEN7686" 116 ></A 117 ><H2 118 >Arguments</H2 119 ><P 120 ></P 121 ><DIV 122 CLASS="VARIABLELIST" 123 ><DL 124 ><DT 125 ><CODE 126 CLASS="PARAMETER" 127 >fd</CODE 128 ></DT 129 ><DD 130 ><P 131 >File descriptor returned by <A 132 HREF="r14090.htm" 133 ><CODE 134 CLASS="FUNCTION" 135 >open()</CODE 136 ></A 137 >.</P 138 ></DD 139 ><DT 140 ><CODE 141 CLASS="PARAMETER" 142 >request</CODE 143 ></DT 144 ><DD 145 ><P 146 >V4L2 ioctl request code as defined in the <A 147 HREF="a16506.htm" 148 >videodev.h</A 149 > header file, for example 150 VIDIOC_QUERYCAP.</P 151 ></DD 152 ><DT 153 ><CODE 154 CLASS="PARAMETER" 155 >argp</CODE 156 ></DT 157 ><DD 158 ><P 159 >Pointer to a function parameter, usually a structure.</P 160 ></DD 161 ></DL 162 ></DIV 163 ></DIV 164 ><DIV 165 CLASS="REFSECT1" 166 ><A 167 NAME="AEN7707" 168 ></A 169 ><H2 170 >Description</H2 171 ><P 172 >The <CODE 173 CLASS="FUNCTION" 174 >ioctl()</CODE 175 > function is used to program 176 V4L2 devices. The argument <CODE 177 CLASS="PARAMETER" 178 >fd</CODE 179 > must be an open 180 file descriptor. An ioctl <CODE 181 CLASS="PARAMETER" 182 >request</CODE 183 > has encoded 184 in it whether the argument is an input, output or read/write 185 parameter, and the size of the argument <CODE 186 CLASS="PARAMETER" 187 >argp</CODE 188 > in 189 bytes. Macros and defines specifying V4L2 ioctl requests are located 190 in the <A 191 HREF="a16506.htm" 192 >videodev.h</A 193 > header file. 194 Applications should use their own copy, not include the version in the 195 kernel sources on the system they compile on. All V4L2 ioctl requests, 196 their respective function and parameters are specified in <A 197 HREF="r7624.htm" 198 >Reference I, <I 199 >Function Reference</I 200 ></A 201 >.</P 202 ></DIV 203 ><DIV 204 CLASS="REFSECT1" 205 ><A 206 NAME="AEN7716" 207 ></A 208 ><H2 209 >Return Value</H2 210 ><P 211 >On success the <CODE 212 CLASS="FUNCTION" 213 >ioctl()</CODE 214 > function returns 215 <SPAN 216 CLASS="RETURNVALUE" 217 >0</SPAN 218 > and does not reset the 219 <CODE 220 CLASS="VARNAME" 221 >errno</CODE 222 > variable. On failure 223 <SPAN 224 CLASS="RETURNVALUE" 225 >-1</SPAN 226 > is returned, when the ioctl takes an 227 output or read/write parameter it remains unmodified, and the 228 <CODE 229 CLASS="VARNAME" 230 >errno</CODE 231 > variable is set appropriately. See below for 232 possible error codes. Generic errors like <SPAN 233 CLASS="ERRORCODE" 234 >EBADF</SPAN 235 > 236 or <SPAN 237 CLASS="ERRORCODE" 238 >EFAULT</SPAN 239 > are not listed in the sections 240 discussing individual ioctl requests.</P 241 ><P 242 >Note ioctls may return undefined error codes. Since errors 243 may have side effects such as a driver reset applications should 244 abort on unexpected errors.</P 245 ><P 246 ></P 247 ><DIV 248 CLASS="VARIABLELIST" 249 ><DL 250 ><DT 251 ><SPAN 252 CLASS="ERRORCODE" 253 >EBADF</SPAN 254 ></DT 255 ><DD 256 ><P 257 ><CODE 258 CLASS="PARAMETER" 259 >fd</CODE 260 > is not a valid open file 261 descriptor.</P 262 ></DD 263 ><DT 264 ><SPAN 265 CLASS="ERRORCODE" 266 >EBUSY</SPAN 267 ></DT 268 ><DD 269 ><P 270 >The property cannot be changed right now. Typically 271 this error code is returned when I/O is in progress or the driver 272 supports multiple opens and another process locked the property.</P 273 ></DD 274 ><DT 275 ><SPAN 276 CLASS="ERRORCODE" 277 >EFAULT</SPAN 278 ></DT 279 ><DD 280 ><P 281 ><CODE 282 CLASS="PARAMETER" 283 >argp</CODE 284 > references an inaccessible 285 memory area.</P 286 ></DD 287 ><DT 288 ><SPAN 289 CLASS="ERRORCODE" 290 >ENOTTY</SPAN 291 ></DT 292 ><DD 293 ><P 294 ><CODE 295 CLASS="PARAMETER" 296 >fd</CODE 297 > is not associated with a 298 character special device.</P 299 ></DD 300 ><DT 301 ><SPAN 302 CLASS="ERRORCODE" 303 >EINVAL</SPAN 304 ></DT 305 ><DD 306 ><P 307 >The <CODE 308 CLASS="PARAMETER" 309 >request</CODE 310 > or the data pointed 311 to by <CODE 312 CLASS="PARAMETER" 313 >argp</CODE 314 > is not valid. This is a very common 315 error code, see the individual ioctl requests listed in <A 316 HREF="r7624.htm" 317 >Reference I, <I 318 >Function Reference</I 319 ></A 320 > for actual causes.</P 321 ></DD 322 ><DT 323 ><SPAN 324 CLASS="ERRORCODE" 325 >ENOMEM</SPAN 326 ></DT 327 ><DD 328 ><P 329 >Not enough physical or virtual memory was available to 330 complete the request.</P 331 ></DD 332 ><DT 333 ><SPAN 334 CLASS="ERRORCODE" 335 >ERANGE</SPAN 336 ></DT 337 ><DD 338 ><P 339 >The application attempted to set a control with the 340 <A 341 HREF="r10104.htm" 342 ><CODE 343 CLASS="CONSTANT" 344 >VIDIOC_S_CTRL</CODE 345 ></A 346 > ioctl to a value which is out of bounds.</P 347 ></DD 348 ></DL 349 ></DIV 350 ></DIV 351 ><DIV 352 CLASS="NAVFOOTER" 353 ><HR 354 ALIGN="LEFT" 355 WIDTH="100%"><TABLE 356 SUMMARY="Footer navigation table" 357 WIDTH="100%" 358 BORDER="0" 359 CELLPADDING="0" 360 CELLSPACING="0" 361 ><TR 362 ><TD 363 WIDTH="33%" 364 ALIGN="left" 365 VALIGN="top" 366 ><A 367 HREF="r7626.htm" 368 ACCESSKEY="P" 369 >Prev</A 370 ></TD 371 ><TD 372 WIDTH="34%" 373 ALIGN="center" 374 VALIGN="top" 375 ><A 376 HREF="book1.htm" 377 ACCESSKEY="H" 378 >Home</A 379 ></TD 380 ><TD 381 WIDTH="33%" 382 ALIGN="right" 383 VALIGN="top" 384 ><A 385 HREF="r7771.htm" 386 ACCESSKEY="N" 387 >Next</A 388 ></TD 389 ></TR 390 ><TR 391 ><TD 392 WIDTH="33%" 393 ALIGN="left" 394 VALIGN="top" 395 >V4L2 close()</TD 396 ><TD 397 WIDTH="34%" 398 ALIGN="center" 399 VALIGN="top" 400 ><A 401 HREF="r7624.htm" 402 ACCESSKEY="U" 403 >Up</A 404 ></TD 405 ><TD 406 WIDTH="33%" 407 ALIGN="right" 408 VALIGN="top" 409 >ioctl VIDIOC_CROPCAP</TD 410 ></TR 411 ></TABLE 412 ></DIV 413 ></BODY 414 ></HTML 415 > 416
