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-.. Permission is granted to copy, distribute and/or modify this
-.. document under the terms of the GNU Free Documentation License,
-.. Version 1.1 or any later version published by the Free Software
-.. Foundation, with no Invariant Sections, no Front-Cover Texts
-.. and no Back-Cover Texts. A copy of the license is included at
-.. Documentation/media/uapi/fdl-appendix.rst.
-..
-.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
-
-.. _dmx-mmap:
-
-*****************
-Digital TV mmap()
-*****************
-
-Name
-====
-
-dmx-mmap - Map device memory into application address space
-
-.. warning:: this API is still experimental
-
-Synopsis
-========
-
-.. code-block:: c
-
- #include <unistd.h>
- #include <sys/mman.h>
-
-
-.. c:function:: void *mmap( void *start, size_t length, int prot, int flags, int fd, off_t offset )
- :name: dmx-mmap
-
-Arguments
-=========
-
-``start``
- Map the buffer to this address in the application's address space.
- When the ``MAP_FIXED`` flag is specified, ``start`` must be a
- multiple of the pagesize and mmap will fail when the specified
- address cannot be used. Use of this option is discouraged;
- applications should just specify a ``NULL`` pointer here.
-
-``length``
- Length of the memory area to map. This must be a multiple of the
- DVB packet length (188, on most drivers).
-
-``prot``
- The ``prot`` argument describes the desired memory protection.
- Regardless of the device type and the direction of data exchange it
- should be set to ``PROT_READ`` | ``PROT_WRITE``, permitting read
- and write access to image buffers. Drivers should support at least
- this combination of flags.
-
-``flags``
- The ``flags`` parameter specifies the type of the mapped object,
- mapping options and whether modifications made to the mapped copy of
- the page are private to the process or are to be shared with other
- references.
-
- ``MAP_FIXED`` requests that the driver selects no other address than
- the one specified. If the specified address cannot be used,
- :ref:`mmap() <dmx-mmap>` will fail. If ``MAP_FIXED`` is specified,
- ``start`` must be a multiple of the pagesize. Use of this option is
- discouraged.
-
- One of the ``MAP_SHARED`` or ``MAP_PRIVATE`` flags must be set.
- ``MAP_SHARED`` allows applications to share the mapped memory with
- other (e. g. child-) processes.
-
- .. note::
-
- The Linux Digital TV applications should not set the
- ``MAP_PRIVATE``, ``MAP_DENYWRITE``, ``MAP_EXECUTABLE`` or ``MAP_ANON``
- flags.
-
-``fd``
- File descriptor returned by :ref:`open() <dmx_fopen>`.
-
-``offset``
- Offset of the buffer in device memory, as returned by
- :ref:`DMX_QUERYBUF` ioctl.
-
-
-Description
-===========
-
-The :ref:`mmap() <dmx-mmap>` function asks to map ``length`` bytes starting at
-``offset`` in the memory of the device specified by ``fd`` into the
-application address space, preferably at address ``start``. This latter
-address is a hint only, and is usually specified as 0.
-
-Suitable length and offset parameters are queried with the
-:ref:`DMX_QUERYBUF` ioctl. Buffers must be allocated with the
-:ref:`DMX_REQBUFS` ioctl before they can be queried.
-
-To unmap buffers the :ref:`munmap() <dmx-munmap>` function is used.
-
-
-Return Value
-============
-
-On success :ref:`mmap() <dmx-mmap>` returns a pointer to the mapped buffer. On
-error ``MAP_FAILED`` (-1) is returned, and the ``errno`` variable is set
-appropriately. Possible error codes are:
-
-EBADF
- ``fd`` is not a valid file descriptor.
-
-EACCES
- ``fd`` is not open for reading and writing.
-
-EINVAL
- The ``start`` or ``length`` or ``offset`` are not suitable. (E. g.
- they are too large, or not aligned on a ``PAGESIZE`` boundary.)
-
- The ``flags`` or ``prot`` value is not supported.
-
- No buffers have been allocated with the
- :ref:`DMX_REQBUFS` ioctl.
-
-ENOMEM
- Not enough physical or virtual memory was available to complete the
- request.