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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-03 20:59:38 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-03 20:59:38 -0700 |
commit | a98f670e41a99f53acb1fb33cee9c6abbb2e6f23 (patch) | |
tree | f8ae10a4cb91758ad7f9422053753a8c5d0f04dc /Documentation/userspace-api/media/dvb/dmx-mmap.rst | |
parent | ee01c4d72adffb7d424535adf630f2955748fa8b (diff) | |
parent | 938b29db3aa9c293c7c1366b16e55e308f1a1ddd (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
...
Diffstat (limited to 'Documentation/userspace-api/media/dvb/dmx-mmap.rst')
-rw-r--r-- | Documentation/userspace-api/media/dvb/dmx-mmap.rst | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/dvb/dmx-mmap.rst b/Documentation/userspace-api/media/dvb/dmx-mmap.rst new file mode 100644 index 000000000000..828ba9df73e2 --- /dev/null +++ b/Documentation/userspace-api/media/dvb/dmx-mmap.rst @@ -0,0 +1,125 @@ +.. 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. |