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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-03 20:59:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-03 20:59:38 -0700
commita98f670e41a99f53acb1fb33cee9c6abbb2e6f23 (patch)
treef8ae10a4cb91758ad7f9422053753a8c5d0f04dc /Documentation/userspace-api/media/dvb/dmx-mmap.rst
parentee01c4d72adffb7d424535adf630f2955748fa8b (diff)
parent938b29db3aa9c293c7c1366b16e55e308f1a1ddd (diff)
Merge tag 'media/v5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull media updates from Mauro Carvalho Chehab: - Media documentation is now split into admin-guide, driver-api and userspace-api books (a longstanding request from Jon); - The media Kconfig was reorganized, in order to make easier to select drivers and their dependencies; - The testing drivers now has a separate directory; - added a new driver for Rockchip Video Decoder IP; - The atomisp staging driver was resurrected. It is meant to work with 4 generations of cameras on Atom-based laptops, tablets and cell phones. So, it seems worth investing time to cleanup this driver and making it in good shape. - Added some V4L2 core ancillary routines to help with h264 codecs; - Added an ov2740 image sensor driver; - The si2157 gained support for Analog TV, which, in turn, added support for some cx231xx and cx23885 boards to also support analog standards; - Added some V4L2 controls (V4L2_CID_CAMERA_ORIENTATION and V4L2_CID_CAMERA_SENSOR_ROTATION) to help identifying where the camera is located at the device; - VIDIOC_ENUM_FMT was extended to support MC-centric devices; - Lots of drivers improvements and cleanups. * tag 'media/v5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (503 commits) media: Documentation: media: Refer to mbus format documentation from CSI-2 docs media: s5k5baf: Replace zero-length array with flexible-array media: i2c: imx219: Drop <linux/clk-provider.h> and <linux/clkdev.h> media: i2c: Add ov2740 image sensor driver media: ov8856: Implement sensor module revision identification media: ov8856: Add devicetree support media: dt-bindings: ov8856: Document YAML bindings media: dvb-usb: Add Cinergy S2 PCIe Dual Port support media: dvbdev: Fix tuner->demod media controller link media: dt-bindings: phy: phy-rockchip-dphy-rx0: move rockchip dphy rx0 bindings out of staging media: staging: dt-bindings: phy-rockchip-dphy-rx0: remove non-used reg property media: atomisp: unify the version for isp2401 a0 and b0 versions media: atomisp: update TODO with the current data media: atomisp: adjust some code at sh_css that could be broken media: atomisp: don't produce errs for ignored IRQs media: atomisp: print IRQ when debugging media: atomisp: isp_mmu: don't use kmem_cache media: atomisp: add a notice about possible leak resources media: atomisp: disable the dynamic and reserved pools media: atomisp: turn on camera before setting it ...
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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/userspace-api/media/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.