[media] demux.h: move documentation overview from device-drivers.tmpl

It is better to keep the documentation overview at the header file,
as this makes easier for developers to remember to fix when needed.
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

Documentation/DocBook/device-drivers.tmpl

@@ -244,70 +244,11 @@ X!Isound/sound_firmware.c
 !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 &#8220;function is not available&#8221;.</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>
+!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>
-
-    <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
-	&#8220;bottom half&#8221; 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>

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.
  */
 
 /**