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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| >V4L2 ioctl()</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN7671" |
| ></A |
| ><H2 |
| >Name</H2 |
| >v4l2-ioctl -- Program a V4L2 device</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN7674" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN7675" |
| ></A |
| ><PRE |
| CLASS="FUNCSYNOPSISINFO" |
| >#include <sys/ioctl.h></PRE |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, void *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7686" |
| ></A |
| ><H2 |
| >Arguments</H2 |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| ></DT |
| ><DD |
| ><P |
| >File descriptor returned by <A |
| HREF="r14090.htm" |
| ><CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| ></A |
| >.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| ></DT |
| ><DD |
| ><P |
| >V4L2 ioctl request code as defined in the <A |
| HREF="a16506.htm" |
| >videodev.h</A |
| > header file, for example |
| VIDIOC_QUERYCAP.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| >Pointer to a function parameter, usually a structure.</P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7707" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >The <CODE |
| CLASS="FUNCTION" |
| >ioctl()</CODE |
| > function is used to program |
| V4L2 devices. The argument <CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| > must be an open |
| file descriptor. An ioctl <CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| > has encoded |
| in it whether the argument is an input, output or read/write |
| parameter, and the size of the argument <CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| > in |
| bytes. Macros and defines specifying V4L2 ioctl requests are located |
| in the <A |
| HREF="a16506.htm" |
| >videodev.h</A |
| > header file. |
| Applications should use their own copy, not include the version in the |
| kernel sources on the system they compile on. All V4L2 ioctl requests, |
| their respective function and parameters are specified in <A |
| HREF="r7624.htm" |
| >Reference I, <I |
| >Function Reference</I |
| ></A |
| >.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7716" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >On success the <CODE |
| CLASS="FUNCTION" |
| >ioctl()</CODE |
| > function returns |
| <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > and does not reset the |
| <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > variable. On failure |
| <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > is returned, when the ioctl takes an |
| output or read/write parameter it remains unmodified, and the |
| <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > variable is set appropriately. See below for |
| possible error codes. Generic errors like <SPAN |
| CLASS="ERRORCODE" |
| >EBADF</SPAN |
| > |
| or <SPAN |
| CLASS="ERRORCODE" |
| >EFAULT</SPAN |
| > are not listed in the sections |
| discussing individual ioctl requests.</P |
| ><P |
| >Note ioctls may return undefined error codes. Since errors |
| may have side effects such as a driver reset applications should |
| abort on unexpected errors.</P |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EBADF</SPAN |
| ></DT |
| ><DD |
| ><P |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| > is not a valid open file |
| descriptor.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EBUSY</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The property cannot be changed right now. Typically |
| this error code is returned when I/O is in progress or the driver |
| supports multiple opens and another process locked the property.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EFAULT</SPAN |
| ></DT |
| ><DD |
| ><P |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| > references an inaccessible |
| memory area.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ENOTTY</SPAN |
| ></DT |
| ><DD |
| ><P |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| > is not associated with a |
| character special device.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The <CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| > or the data pointed |
| to by <CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| > is not valid. This is a very common |
| error code, see the individual ioctl requests listed in <A |
| HREF="r7624.htm" |
| >Reference I, <I |
| >Function Reference</I |
| ></A |
| > for actual causes.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ENOMEM</SPAN |
| ></DT |
| ><DD |
| ><P |
| >Not enough physical or virtual memory was available to |
| complete the request.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >ERANGE</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The application attempted to set a control with the |
| <A |
| HREF="r10104.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_S_CTRL</CODE |
| ></A |
| > ioctl to a value which is out of bounds.</P |
| ></DD |
| ></DL |
| ></DIV |
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