diff options
| -rw-r--r-- | Documentation/DocBook/device-drivers.tmpl | 71 | ||||
| -rw-r--r-- | drivers/media/dvb-core/demux.h | 67 |
2 files changed, 71 insertions, 67 deletions
diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl index 42a2d8593e39..c2bc8f779a9b 100644 --- a/Documentation/DocBook/device-drivers.tmpl +++ b/Documentation/DocBook/device-drivers.tmpl @@ -243,71 +243,12 @@ X!Isound/sound_firmware.c !Idrivers/media/dvb-core/dvb_math.h !Idrivers/media/dvb-core/dvb_ringbuffer.h !Idrivers/media/dvb-core/dvbdev.h - <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> - + <sect1><title>Digital TV Demux API</title> +!Pdrivers/media/dvb-core/demux.h Digital TV Demux API + </sect1> + <sect1><title>Demux Callback API</title> +!Pdrivers/media/dvb-core/demux.h Demux Callback API + </sect1> !Idrivers/media/dvb-core/demux.h </sect1> <sect1><title>Remote Controller devices</title> diff --git a/drivers/media/dvb-core/demux.h b/drivers/media/dvb-core/demux.h index ccc1f43cb9a9..f8014aabf37b 100644 --- a/drivers/media/dvb-core/demux.h +++ b/drivers/media/dvb-core/demux.h @@ -32,6 +32,49 @@ #include <linux/time.h> #include <linux/dvb/dmx.h> +/** + * DOC: Digital TV Demux API + * + * 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 demux.h and located in + * drivers/media/dvb-core. + * + * 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. + * + * 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. + * + * 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 + * &dmx_demux. 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. + * + * 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 API function is called from network + * device code, the function must not sleep. + */ + /* * Common definitions */ @@ -187,8 +230,28 @@ struct dmx_section_feed { int (*stop_filtering)(struct dmx_section_feed *feed); }; -/* - * Callback functions +/** + * DOC: 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 dmx_ts_cb() and dmx_section_cb() + * callbacks. */ /** |