Documentation/DocBook/media/v4l/media-func-open.xml

   1 <refentry id="media-func-open">
   2   <refmeta>
   3     <refentrytitle>media open()</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>media-open</refname>
   9     <refpurpose>Open a media device</refpurpose>
  10   </refnamediv>
  11
  12   <refsynopsisdiv>
  13     <funcsynopsis>
  14       <funcsynopsisinfo>#include &lt;fcntl.h&gt;</funcsynopsisinfo>
  15       <funcprototype>
  16         <funcdef>int <function>open</function></funcdef>
  17         <paramdef>const char *<parameter>device_name</parameter></paramdef>
  18         <paramdef>int <parameter>flags</parameter></paramdef>
  19       </funcprototype>
  20     </funcsynopsis>
  21   </refsynopsisdiv>
  22
  23   <refsect1>
  24     <title>Arguments</title>
  25
  26     <variablelist>
  27       <varlistentry>
  28         <term><parameter>device_name</parameter></term>
  29         <listitem>
  30           <para>Device to be opened.</para>
  31         </listitem>
  32       </varlistentry>
  33       <varlistentry>
  34         <term><parameter>flags</parameter></term>
  35         <listitem>
  36           <para>Open flags. Access mode must be either <constant>O_RDONLY</constant>
  37           or <constant>O_RDWR</constant>. Other flags have no effect.</para>
  38         </listitem>
  39       </varlistentry>
  40     </variablelist>
  41   </refsect1>
  42   <refsect1>
  43     <title>Description</title>
  44     <para>To open a media device applications call <function>open()</function>
  45     with the desired device name. The function has no side effects; the device
  46     configuration remain unchanged.</para>
  47     <para>When the device is opened in read-only mode, attemps to modify its
  48     configuration will result in an error, and <varname>errno</varname> will be
  49     set to <errorcode>EBADF</errorcode>.</para>
  50   </refsect1>
  51   <refsect1>
  52     <title>Return Value</title>
  53
  54     <para><function>open</function> returns the new file descriptor on success.
  55     On error, -1 is returned, and <varname>errno</varname> is set appropriately.
  56     Possible error codes are:</para>
  57
  58     <variablelist>
  59       <varlistentry>
  60         <term><errorcode>EACCES</errorcode></term>
  61         <listitem>
  62           <para>The requested access to the file is not allowed.</para>
  63         </listitem>
  64       </varlistentry>
  65       <varlistentry>
  66         <term><errorcode>EMFILE</errorcode></term>
  67         <listitem>
  68           <para>The  process  already  has  the  maximum number of files open.
  69           </para>
  70         </listitem>
  71       </varlistentry>
  72       <varlistentry>
  73         <term><errorcode>ENFILE</errorcode></term>
  74         <listitem>
  75           <para>The system limit on the total number of open files has been
  76           reached.</para>
  77         </listitem>
  78       </varlistentry>
  79       <varlistentry>
  80         <term><errorcode>ENOMEM</errorcode></term>
  81         <listitem>
  82           <para>Insufficient kernel memory was available.</para>
  83         </listitem>
  84       </varlistentry>
  85       <varlistentry>
  86         <term><errorcode>ENXIO</errorcode></term>
  87         <listitem>
  88           <para>No device corresponding to this device special file exists.
  89           </para>
  90         </listitem>
  91       </varlistentry>
  92     </variablelist>
  93   </refsect1>
  94 </refentry>