forked from Minki/linux
c6401af669
This removes comment tags intended for emacs configuration from 67 files in the Media API DocBook. Such comments are not really helpful and violate the coding style rules. Signed-off-by: Sylwester Nawrocki <snjw23@gmail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
114 lines
3.4 KiB
XML
114 lines
3.4 KiB
XML
<refentry id="func-open">
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<refmeta>
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<refentrytitle>V4L2 open()</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>v4l2-open</refname>
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<refpurpose>Open a V4L2 device</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <fcntl.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>open</function></funcdef>
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<paramdef>const char *<parameter>device_name</parameter></paramdef>
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<paramdef>int <parameter>flags</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>device_name</parameter></term>
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<listitem>
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<para>Device to be opened.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>flags</parameter></term>
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<listitem>
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<para>Open flags. Access mode must be
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<constant>O_RDWR</constant>. This is just a technicality, input devices
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still support only reading and output devices only writing.</para>
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<para>When the <constant>O_NONBLOCK</constant> flag is
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given, the read() function and the &VIDIOC-DQBUF; ioctl will return
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the &EAGAIN; when no data is available or no buffer is in the driver
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outgoing queue, otherwise these functions block until data becomes
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available. All V4L2 drivers exchanging data with applications must
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support the <constant>O_NONBLOCK</constant> flag.</para>
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<para>Other flags have no effect.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To open a V4L2 device applications call
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<function>open()</function> with the desired device name. This
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function has no side effects; all data format parameters, current
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input or output, control values or other properties remain unchanged.
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At the first <function>open()</function> call after loading the driver
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they will be reset to default values, drivers are never in an
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undefined state.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success <function>open</function> returns the new file
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descriptor. On error -1 is returned, and the <varname>errno</varname>
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variable is set appropriately. Possible error codes are:</para>
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<variablelist>
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<varlistentry>
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<term><errorcode>EACCES</errorcode></term>
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<listitem>
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<para>The caller has no permission to access the
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device.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>The driver does not support multiple opens and the
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device is already in use.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENXIO</errorcode></term>
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<listitem>
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<para>No device corresponding to this device special file
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exists.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENOMEM</errorcode></term>
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<listitem>
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<para>Not enough kernel memory was available to complete the
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request.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EMFILE</errorcode></term>
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<listitem>
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<para>The process already has the maximum number of
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files open.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENFILE</errorcode></term>
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<listitem>
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<para>The limit on the total number of files open on the
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system has been reached.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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