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| -rw-r--r-- | Documentation/DocBook/device-drivers.tmpl | 77 |
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diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl index 8d5620aeaf36..42a2d8593e39 100644 --- a/Documentation/DocBook/device-drivers.tmpl +++ b/Documentation/DocBook/device-drivers.tmpl @@ -239,21 +239,86 @@ X!Isound/sound_firmware.c </sect1> <sect1><title>Digital TV (DVB) devices</title> !Idrivers/media/dvb-core/dvb_ca_en50221.h -!Idrivers/media/dvb-core/demux.h !Idrivers/media/dvb-core/dvb_frontend.h !Idrivers/media/dvb-core/dvb_math.h !Idrivers/media/dvb-core/dvb_ringbuffer.h !Idrivers/media/dvb-core/dvbdev.h - </sect1> - <sect1><title>Remote Controller devices</title> + <sect1><title>Digital TV Demux API</title> + <para>The kernel demux API 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 API is named + <constant>demux.h</constant> and located in + <constant>drivers/media/dvb-core</constant>.</para> + + <para>The demux API 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 API, it receives a pointer to the API of that + resource.</para> + <para>Each demux receives its TS input from a DVB front-end or from + memory, as set via this demux API. In a system with more than one + front-end, the API 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 API only controls front-ends regarding to their connections + with demuxes; the APIs used to set the other front-end parameters, + such as tuning, are not defined in this document.</para> + <para>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 <constant>dmx_demux</constant>. For example, + a demux interface might support Section filtering, but not PES + filtering. The API 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”.</para> + <para>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.</para> + <para>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 API function + is called from network device code, the function must not sleep. + </para> + </sect1> + + <section id="demux_callback_api"> + <title>Demux Callback API</title> + <para>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.</para> + <para>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.</para> + <para>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.</para> + <para>This mechanism is implemented by + <link linkend='API-dmx-ts-cb'>dmx_ts_cb()</link> and + <link linkend='API-dmx-section-cb'>dmx_section_cb()</link>.</para> + </section> + +!Idrivers/media/dvb-core/demux.h + </sect1> + <sect1><title>Remote Controller devices</title> !Iinclude/media/rc-core.h !Iinclude/media/lirc_dev.h - </sect1> - <sect1><title>Media Controller devices</title> + </sect1> + <sect1><title>Media Controller devices</title> !Iinclude/media/media-device.h !Iinclude/media/media-devnode.h !Iinclude/media/media-entity.h - </sect1> + </sect1> </chapter> |