Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/Documentation/DocBook/v4l/media-ioc-setup-link.xml
10821 views
1
<refentry id="media-ioc-setup-link">

2
  <refmeta>

3
    <refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>

4
    &manvol;

5
  </refmeta>

6


7
  <refnamediv>

8
    <refname>MEDIA_IOC_SETUP_LINK</refname>

9
    <refpurpose>Modify the properties of a link</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 media_link_desc *<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>File descriptor returned by

31
	  <link linkend='media-func-open'><function>open()</function></link>.</para>

32
	</listitem>

33
      </varlistentry>

34
      <varlistentry>

35
	<term><parameter>request</parameter></term>

36
	<listitem>

37
	  <para>MEDIA_IOC_SETUP_LINK</para>

38
	</listitem>

39
      </varlistentry>

40
      <varlistentry>

41
	<term><parameter>argp</parameter></term>

42
	<listitem>

43
	  <para></para>

44
	</listitem>

45
      </varlistentry>

46
    </variablelist>

47
  </refsect1>

48


49
  <refsect1>

50
    <title>Description</title>

51


52
    <para>To change link properties applications fill a &media-link-desc; with

53
    link identification information (source and sink pad) and the new requested

54
    link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to

55
    that structure.</para>

56
    <para>The only configurable property is the <constant>ENABLED</constant>

57
    link flag to enable/disable a link. Links marked with the

58
    <constant>IMMUTABLE</constant> link flag can not be enabled or disabled.

59
    </para>

60
    <para>Link configuration has no side effect on other links. If an enabled

61
    link at the sink pad prevents the link from being enabled, the driver

62
    returns with an &EBUSY;.</para>

63
    <para>Only links marked with the <constant>DYNAMIC</constant> link flag can

64
    be enabled/disabled while streaming media data. Attempting to enable or

65
    disable a streaming non-dynamic link will return an &EBUSY;.</para>

66
    <para>If the specified link can't be found the driver returns with an

67
    &EINVAL;.</para>

68
  </refsect1>

69


70
  <refsect1>

71
    &return-value;

72


73
    <variablelist>

74
      <varlistentry>

75
	<term><errorcode>EBUSY</errorcode></term>

76
	<listitem>

77
	  <para>The link properties can't be changed because the link is

78
	  currently busy. This can be caused, for instance, by an active media

79
	  stream (audio or video) on the link. The ioctl shouldn't be retried if

80
	  no other action is performed before to fix the problem.</para>

81
	</listitem>

82
      </varlistentry>

83
      <varlistentry>

84
	<term><errorcode>EINVAL</errorcode></term>

85
	<listitem>

86
	  <para>The &media-link-desc; references a non-existing link, or the

87
	  link is immutable and an attempt to modify its configuration was made.

88
	  </para>

89
	</listitem>

90
      </varlistentry>

91
    </variablelist>

92
  </refsect1>

93
</refentry>

94


95