mirror of https://gitee.com/openkylin/linux.git
77 lines
2.2 KiB
XML
77 lines
2.2 KiB
XML
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<refentry id="func-munmap">
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<refmeta>
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<refentrytitle>V4L2 munmap()</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>v4l2-munmap</refname>
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<refpurpose>Unmap device memory</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>
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#include <unistd.h>
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#include <sys/mman.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>munmap</function></funcdef>
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<paramdef>void *<parameter>start</parameter></paramdef>
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<paramdef>size_t <parameter>length</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>start</parameter></term>
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<listitem>
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<para>Address of the mapped buffer as returned by the
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&func-mmap; function.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>length</parameter></term>
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<listitem>
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<para>Length of the mapped buffer. This must be the same
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value as given to <function>mmap()</function> and returned by the
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driver in the &v4l2-buffer; <structfield>length</structfield>
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field for the single-planar API and in the &v4l2-plane;
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<structfield>length</structfield> field for the multi-planar API.</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>Unmaps a previously with the &func-mmap; function mapped
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buffer and frees it, if possible. <!-- ? This function (not freeing)
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has no impact on I/O in progress, specifically it does not imply
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&VIDIOC-STREAMOFF; to terminate I/O. Unmapped buffers can still be
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enqueued, dequeued or queried, they are just not accessible by the
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application.--></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>munmap()</function> returns 0, on
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failure -1 and the <varname>errno</varname> variable is set
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appropriately:</para>
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The <parameter>start</parameter> or
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<parameter>length</parameter> is incorrect, or no buffers have been
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mapped yet.</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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