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Diffstat (limited to 'Documentation/DocBook/media/v4l/func-select.xml')
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diff --git a/Documentation/DocBook/media/v4l/func-select.xml b/Documentation/DocBook/media/v4l/func-select.xml deleted file mode 100644 index e12a60d9b..000000000 --- a/Documentation/DocBook/media/v4l/func-select.xml +++ /dev/null @@ -1,130 +0,0 @@ -<refentry id="func-select"> - <refmeta> - <refentrytitle>V4L2 select()</refentrytitle> - &manvol; - </refmeta> - - <refnamediv> - <refname>v4l2-select</refname> - <refpurpose>Synchronous I/O multiplexing</refpurpose> - </refnamediv> - - <refsynopsisdiv> - <funcsynopsis> - <funcsynopsisinfo> -#include <sys/time.h> -#include <sys/types.h> -#include <unistd.h></funcsynopsisinfo> - <funcprototype> - <funcdef>int <function>select</function></funcdef> - <paramdef>int <parameter>nfds</parameter></paramdef> - <paramdef>fd_set *<parameter>readfds</parameter></paramdef> - <paramdef>fd_set *<parameter>writefds</parameter></paramdef> - <paramdef>fd_set *<parameter>exceptfds</parameter></paramdef> - <paramdef>struct timeval *<parameter>timeout</parameter></paramdef> - </funcprototype> - </funcsynopsis> - </refsynopsisdiv> - - <refsect1> - <title>Description</title> - - <para>With the <function>select()</function> function applications -can suspend execution until the driver has captured data or is ready -to accept data for output.</para> - - <para>When streaming I/O has been negotiated this function waits -until a buffer has been filled or displayed and can be dequeued with -the &VIDIOC-DQBUF; ioctl. When buffers are already in the outgoing -queue of the driver the function returns immediately.</para> - - <para>On success <function>select()</function> returns the total -number of bits set in the <structname>fd_set</structname>s. When the -function timed out it returns a value of zero. On failure it returns -<returnvalue>-1</returnvalue> and the <varname>errno</varname> -variable is set appropriately. When the application did not call -&VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the -<function>select()</function> function succeeds, setting the bit of -the file descriptor in <parameter>readfds</parameter> or -<parameter>writefds</parameter>, but subsequent &VIDIOC-DQBUF; calls -will fail.<footnote><para>The Linux kernel implements -<function>select()</function> like the &func-poll; function, but -<function>select()</function> cannot return a -<constant>POLLERR</constant>.</para> - </footnote></para> - - <para>When use of the <function>read()</function> function has -been negotiated and the driver does not capture yet, the -<function>select()</function> function starts capturing. When that -fails, <function>select()</function> returns successful and a -subsequent <function>read()</function> call, which also attempts to -start capturing, will return an appropriate error code. When the -driver captures continuously (as opposed to, for example, still -images) and data is already available the -<function>select()</function> function returns immediately.</para> - - <para>When use of the <function>write()</function> function has -been negotiated the <function>select()</function> function just waits -until the driver is ready for a non-blocking -<function>write()</function> call.</para> - - <para>All drivers implementing the <function>read()</function> or -<function>write()</function> function or streaming I/O must also -support the <function>select()</function> function.</para> - - <para>For more details see the <function>select()</function> -manual page.</para> - - </refsect1> - - <refsect1> - <title>Return Value</title> - - <para>On success, <function>select()</function> returns the number -of descriptors contained in the three returned descriptor sets, which -will be zero if the timeout expired. On error -<returnvalue>-1</returnvalue> is returned, and the -<varname>errno</varname> variable is set appropriately; the sets and -<parameter>timeout</parameter> are undefined. Possible error codes -are:</para> - - <variablelist> - <varlistentry> - <term><errorcode>EBADF</errorcode></term> - <listitem> - <para>One or more of the file descriptor sets specified a -file descriptor that is not open.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EBUSY</errorcode></term> - <listitem> - <para>The driver does not support multiple read or write -streams and the device is already in use.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EFAULT</errorcode></term> - <listitem> - <para>The <parameter>readfds</parameter>, -<parameter>writefds</parameter>, <parameter>exceptfds</parameter> or -<parameter>timeout</parameter> pointer references an inaccessible memory -area.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EINTR</errorcode></term> - <listitem> - <para>The call was interrupted by a signal.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EINVAL</errorcode></term> - <listitem> - <para>The <parameter>nfds</parameter> argument is less than -zero or greater than <constant>FD_SETSIZE</constant>.</para> - </listitem> - </varlistentry> - </variablelist> - </refsect1> -</refentry> |