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authorMauro Carvalho Chehab <mchehab+huawei@kernel.org>2020-03-04 10:50:14 +0100
committerMauro Carvalho Chehab <mchehab+huawei@kernel.org>2020-04-14 10:32:45 +0200
commitff768f596fa19e719c88fbc9bd65e13145d944e7 (patch)
tree8574b980ade74110380566b7f07f84710db37fcd /Documentation/media/kapi/dtv-demux.rst
parent54f38fcae536ea202ce7d6a359521492fba30c1f (diff)
media: docs: kAPI docs: move them to driver-api
All those documents describe the media driver API. So, move them to the right place within the Kernel documentation. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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-.. SPDX-License-Identifier: GPL-2.0
-
-Digital TV Demux kABI
----------------------
-
-Digital TV Demux
-~~~~~~~~~~~~~~~~
-
-The Kernel Digital TV Demux kABI defines a driver-internal interface for
-registering low-level, hardware specific driver to a hardware independent
-demux layer. It is only of interest for Digital TV device driver writers.
-The header file for this kABI is named ``demux.h`` and located in
-``include/media``.
-
-The demux kABI should be implemented for each demux in the system. It is
-used to select the TS source of a demux and to manage the demux resources.
-When the demux client allocates a resource via the demux kABI, it receives
-a pointer to the kABI of that resource.
-
-Each demux receives its TS input from a DVB front-end or from memory, as
-set via this demux kABI. In a system with more than one front-end, the kABI
-can be used to select one of the DVB front-ends as a TS source for a demux,
-unless this is fixed in the HW platform.
-
-The demux kABI only controls front-ends regarding to their connections with
-demuxes; the kABI used to set the other front-end parameters, such as
-tuning, are devined via the Digital TV Frontend kABI.
-
-The functions that implement the abstract interface demux should be defined
-static or module private and registered to the Demux core for external
-access. It is not necessary to implement every function in the struct
-:c:type:`dmx_demux`. For example, a demux interface might support Section filtering,
-but not PES filtering. The kABI client is expected to check the value of any
-function pointer before calling the function: the value of ``NULL`` means
-that the function is not available.
-
-Whenever the functions of the demux API modify shared data, the
-possibilities of lost update and race condition problems should be
-addressed, e.g. by protecting parts of code with mutexes.
-
-Note that functions called from a bottom half context must not sleep.
-Even a simple memory allocation without using ``GFP_ATOMIC`` can result in a
-kernel thread being put to sleep if swapping is needed. For example, the
-Linux Kernel calls the functions of a network device interface from a
-bottom half context. Thus, if a demux kABI function is called from network
-device code, the function must not sleep.
-
-Demux Callback API
-~~~~~~~~~~~~~~~~~~
-
-This kernel-space API comprises the callback functions that deliver filtered
-data to the demux client. Unlike the other DVB kABIs, these functions are
-provided by the client and called from the demux code.
-
-The function pointers of this abstract interface are not packed into a
-structure as in the other demux APIs, because the callback functions are
-registered and used independent of each other. As an example, it is possible
-for the API client to provide several callback functions for receiving TS
-packets and no callbacks for PES packets or sections.
-
-The functions that implement the callback API need not be re-entrant: when
-a demux driver calls one of these functions, the driver is not allowed to
-call the function again before the original call returns. If a callback is
-triggered by a hardware interrupt, it is recommended to use the Linux
-bottom half mechanism or start a tasklet instead of making the callback
-function call directly from a hardware interrupt.
-
-This mechanism is implemented by :c:func:`dmx_ts_cb()` and :c:func:`dmx_section_cb()`
-callbacks.
-
-Digital TV Demux device registration functions and data structures
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. kernel-doc:: include/media/dmxdev.h
-
-High-level Digital TV demux interface
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. kernel-doc:: include/media/dvb_demux.h
-
-Driver-internal low-level hardware specific driver demux interface
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. kernel-doc:: include/media/demux.h