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[media] libv4l-introduction.rst: improve crossr-references
Use C cross-references to mention the V4L2 API calls on all
places it occurs inside this file.
While here, also mark constants as such.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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Documentation/media/uapi/v4l/libv4l-introduction.rst
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Documentation/media/uapi/v4l/libv4l-introduction.rst
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The common file operation methods are provided by libv4l.
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Those functions operate just like glibc
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open/close/dup/ioctl/read/mmap/munmap:
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Those functions operate just like the gcc function ``dup()`` and
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V4L2 functions
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:c:func:`open() <v4l2-open>`, :c:func:`close() <v4l2-close>`,
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:c:func:`ioctl() <v4l2-ioctl>`, :c:func:`read() <v4l2-read>`,
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:c:func:`mmap() <v4l2-mmap>` and :c:func:`munmap() <v4l2-munmap>`:
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.. c:function:: int v4l2_open(const char *file, int oflag, ...)
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operates like the standard :ref:`open() <func-open>` function.
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operates like the :c:func:`open() <v4l2-open>` function.
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.. c:function:: int v4l2_close(int fd)
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operates like the standard :ref:`close() <func-close>` function.
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operates like the :c:func:`close() <v4l2-close>` function.
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.. c:function:: int v4l2_dup(int fd)
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operates like the standard dup() function, duplicating a file handler.
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operates like the libc ``dup()`` function, duplicating a file handler.
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.. c:function:: int v4l2_ioctl (int fd, unsigned long int request, ...)
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operates like the standard :ref:`ioctl() <func-ioctl>` function.
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operates like the :c:func:`ioctl() <v4l2-ioctl>` function.
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.. c:function:: int v4l2_read (int fd, void* buffer, size_t n)
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operates like the standard :ref:`read() <func-read>` function.
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operates like the :c:func:`read() <v4l2-read>` function.
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.. c:function:: void v4l2_mmap(void *start, size_t length, int prot, int flags, int fd, int64_t offset);
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operates like the standard :ref:`mmap() <func-mmap>` function.
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operates like the :c:func:`munmap() <v4l2-munmap>` function.
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.. c:function:: int v4l2_munmap(void *_start, size_t length);
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operates like the standard :ref:`munmap() <func-munmap>` function.
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operates like the :c:func:`munmap() <v4l2-munmap>` function.
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Those functions provide additional control:
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.. c:function:: int v4l2_fd_open(int fd, int v4l2_flags)
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opens an already opened fd for further use through v4l2lib and possibly
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modify libv4l2's default behavior through the v4l2_flags argument.
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Currently, v4l2_flags can be ``V4L2_DISABLE_CONVERSION``, to disable
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modify libv4l2's default behavior through the ``v4l2_flags`` argument.
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Currently, ``v4l2_flags`` can be ``V4L2_DISABLE_CONVERSION``, to disable
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format conversion.
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.. c:function:: int v4l2_set_control(int fd, int cid, int value)
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v4l1compat.so wrapper library
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=============================
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This library intercepts calls to open/close/ioctl/mmap/mmunmap
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This library intercepts calls to
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:c:func:`open() <v4l2-open>`, :c:func:`close() <v4l2-close>`,
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:c:func:`ioctl() <v4l2-ioctl>`, :c:func:`mmap() <v4l2-mmap>` and
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:c:func:`munmap() <v4l2-munmap>`
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operations and redirects them to the libv4l counterparts, by using
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LD_PRELOAD=/usr/lib/v4l1compat.so. It also emulates V4L1 calls via V4L2
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``LD_PRELOAD=/usr/lib/v4l1compat.so``. It also emulates V4L1 calls via V4L2
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API.
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It allows usage of binary legacy applications that still don't use