Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/Documentation/DocBook/v4l/media-func-ioctl.xml
10823 views
1
<refentry id="media-func-ioctl">

2
  <refmeta>

3
    <refentrytitle>media ioctl()</refentrytitle>

4
    &manvol;

5
  </refmeta>

6


7
  <refnamediv>

8
    <refname>media-ioctl</refname>

9
    <refpurpose>Control a media device</refpurpose>

10
  </refnamediv>

11


12
  <refsynopsisdiv>

13
    <funcsynopsis>

14
      <funcsynopsisinfo>#include &lt;sys/ioctl.h&gt;</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>Media ioctl request code as defined in the media.h header file,

38
	  for example MEDIA_IOC_SETUP_LINK.</para>

39
	</listitem>

40
      </varlistentry>

41
      <varlistentry>

42
	<term><parameter>argp</parameter></term>

43
	<listitem>

44
	  <para>Pointer to a request-specific structure.</para>

45
	</listitem>

46
      </varlistentry>

47
    </variablelist>

48
  </refsect1>

49


50
  <refsect1>

51
    <title>Description</title>

52
    <para>The <function>ioctl()</function> function manipulates media device

53
    parameters. The argument <parameter>fd</parameter> must be an open file

54
    descriptor.</para>

55
    <para>The ioctl <parameter>request</parameter> code specifies the media

56
    function to be called. It has encoded in it whether the argument is an

57
    input, output or read/write parameter, and the size of the argument

58
    <parameter>argp</parameter> in bytes.</para>

59
    <para>Macros and structures definitions specifying media ioctl requests and

60
    their parameters are located in the media.h header file. All media ioctl

61
    requests, their respective function and parameters are specified in

62
    <xref linkend="media-user-func" />.</para>

63
  </refsect1>

64


65
  <refsect1>

66
    <title>Return Value</title>

67


68
    <para><function>ioctl()</function> returns <returnvalue>0</returnvalue> on

69
    success. On failure, <returnvalue>-1</returnvalue> is returned, and the

70
    <varname>errno</varname> variable is set appropriately. Generic error codes

71
    are listed below, and request-specific error codes are listed in the

72
    individual requests descriptions.</para>

73
    <para>When an ioctl that takes an output or read/write parameter fails,

74
    the parameter remains unmodified.</para>

75


76
    <variablelist>

77
      <varlistentry>

78
	<term><errorcode>EBADF</errorcode></term>

79
	<listitem>

80
	  <para><parameter>fd</parameter> is not a valid open file descriptor.

81
	  </para>

82
	</listitem>

83
      </varlistentry>

84
      <varlistentry>

85
	<term><errorcode>EFAULT</errorcode></term>

86
	<listitem>

87
	  <para><parameter>argp</parameter> references an inaccessible memory

88
	  area.</para>

89
	</listitem>

90
      </varlistentry>

91
      <varlistentry>

92
	<term><errorcode>EINVAL</errorcode></term>

93
	<listitem>

94
	  <para>The <parameter>request</parameter> or the data pointed to by

95
	  <parameter>argp</parameter> is not valid. This is a very common error

96
	  code, see the individual ioctl requests listed in

97
	  <xref linkend="media-user-func" /> for actual causes.</para>

98
	</listitem>

99
      </varlistentry>

100
      <varlistentry>

101
	<term><errorcode>ENOMEM</errorcode></term>

102
	<listitem>

103
	  <para>Insufficient kernel memory was available to complete the

104
	  request.</para>

105
	</listitem>

106
      </varlistentry>

107
      <varlistentry>

108
	<term><errorcode>ENOTTY</errorcode></term>

109
	<listitem>

110
	  <para><parameter>fd</parameter> is  not  associated  with  a character

111
	  special device.</para>

112
	</listitem>

113
      </varlistentry>

114
    </variablelist>

115
  </refsect1>

116
</refentry>

117


118