Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="func-ioctl"> 2 <refmeta> 3 <refentrytitle>V4L2 ioctl()</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>v4l2-ioctl</refname> 9 <refpurpose>Program a V4L2 device</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcsynopsisinfo>#include <sys/ioctl.h></funcsynopsisinfo> 15 <funcprototype> 16 <funcdef>int <function>ioctl</function></funcdef> 17 <paramdef>int <parameter>fd</parameter></paramdef> 18 <paramdef>int <parameter>request</parameter></paramdef> 19 <paramdef>void *<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 </refsynopsisdiv> 23 24 <refsect1> 25 <title>Arguments</title> 26 27 <variablelist> 28 <varlistentry> 29 <term><parameter>fd</parameter></term> 30 <listitem> 31 <para>&fd;</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>V4L2 ioctl request code as defined in the <filename>videodev2.h</filename> header file, for example 38 VIDIOC_QUERYCAP.</para> 39 </listitem> 40 </varlistentry> 41 <varlistentry> 42 <term><parameter>argp</parameter></term> 43 <listitem> 44 <para>Pointer to a function parameter, usually a structure.</para> 45 </listitem> 46 </varlistentry> 47 </variablelist> 48 </refsect1> 49 50 <refsect1> 51 <title>Description</title> 52 53 <para>The <function>ioctl()</function> function is used to program 54 V4L2 devices. The argument <parameter>fd</parameter> must be an open 55 file descriptor. An ioctl <parameter>request</parameter> has encoded 56 in it whether the argument is an input, output or read/write 57 parameter, and the size of the argument <parameter>argp</parameter> in 58 bytes. Macros and defines specifying V4L2 ioctl requests are located 59 in the <filename>videodev2.h</filename> header file. 60 Applications should use their own copy, not include the version in the 61 kernel sources on the system they compile on. All V4L2 ioctl requests, 62 their respective function and parameters are specified in <xref 63 linkend="user-func" />.</para> 64 </refsect1> 65 66 <refsect1> 67 <title>Return Value</title> 68 69 <para>On success the <function>ioctl()</function> function returns 70 <returnvalue>0</returnvalue> and does not reset the 71 <varname>errno</varname> variable. On failure 72 <returnvalue>-1</returnvalue> is returned, when the ioctl takes an 73 output or read/write parameter it remains unmodified, and the 74 <varname>errno</varname> variable is set appropriately. See below for 75 possible error codes. Generic errors like <errorcode>EBADF</errorcode> 76 or <errorcode>EFAULT</errorcode> are not listed in the sections 77 discussing individual ioctl requests.</para> 78 <para>Note ioctls may return undefined error codes. Since errors 79 may have side effects such as a driver reset applications should 80 abort on unexpected errors.</para> 81 82 <variablelist> 83 <varlistentry> 84 <term><errorcode>EBADF</errorcode></term> 85 <listitem> 86 <para><parameter>fd</parameter> is not a valid open file 87 descriptor.</para> 88 </listitem> 89 </varlistentry> 90 <varlistentry> 91 <term><errorcode>EBUSY</errorcode></term> 92 <listitem> 93 <para>The property cannot be changed right now. Typically 94 this error code is returned when I/O is in progress or the driver 95 supports multiple opens and another process locked the property.</para> 96 </listitem> 97 </varlistentry> 98 <varlistentry> 99 <term><errorcode>EFAULT</errorcode></term> 100 <listitem> 101 <para><parameter>argp</parameter> references an inaccessible 102 memory area.</para> 103 </listitem> 104 </varlistentry> 105 <varlistentry> 106 <term><errorcode>ENOTTY</errorcode></term> 107 <listitem> 108 <para><parameter>fd</parameter> is not associated with a 109 character special device.</para> 110 </listitem> 111 </varlistentry> 112 <varlistentry> 113 <term><errorcode>EINVAL</errorcode></term> 114 <listitem> 115 <para>The <parameter>request</parameter> or the data pointed 116 to by <parameter>argp</parameter> is not valid. This is a very common 117 error code, see the individual ioctl requests listed in <xref 118 linkend="user-func" /> for actual causes.</para> 119 </listitem> 120 </varlistentry> 121 <varlistentry> 122 <term><errorcode>ENOMEM</errorcode></term> 123 <listitem> 124 <para>Not enough physical or virtual memory was available to 125 complete the request.</para> 126 </listitem> 127 </varlistentry> 128 <varlistentry> 129 <term><errorcode>ERANGE</errorcode></term> 130 <listitem> 131 <para>The application attempted to set a control with the 132 &VIDIOC-S-CTRL; ioctl to a value which is out of bounds.</para> 133 </listitem> 134 </varlistentry> 135 </variablelist> 136 </refsect1> 137 </refentry> 138 139 <!-- 140 Local Variables: 141 mode: sgml 142 sgml-parent-document: "v4l2.sgml" 143 indent-tabs-mode: nil 144 End: 145 -->
