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<title>Kernel 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
DVB device driver writers. The header file for this API is named <emphasis role="tt">demux.h</emphasis> and located in
<emphasis role="tt">drivers/media/dvb-core</emphasis>.
</para>
<para>Maintainer note: This section must be reviewed. It is probably out of date.
</para>
<section id="kernel_demux_data_types">
<title>Kernel Demux Data Types</title>
<section id="dmx_success_t">
<title>dmx_success_t</title>
<programlisting>
typedef enum {
DMX_OK = 0, /&#x22C6; Received Ok &#x22C6;/
DMX_LENGTH_ERROR, /&#x22C6; Incorrect length &#x22C6;/
DMX_OVERRUN_ERROR, /&#x22C6; Receiver ring buffer overrun &#x22C6;/
DMX_CRC_ERROR, /&#x22C6; Incorrect CRC &#x22C6;/
DMX_FRAME_ERROR, /&#x22C6; Frame alignment error &#x22C6;/
DMX_FIFO_ERROR, /&#x22C6; Receiver FIFO overrun &#x22C6;/
DMX_MISSED_ERROR /&#x22C6; Receiver missed packet &#x22C6;/
} dmx_success_t;
</programlisting>
</section>
<section id="ts_filter_types">
<title>TS filter types</title>
<programlisting>
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; TS packet reception &#x22C6;/
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; TS filter type for set_type() &#x22C6;/
#define TS_PACKET 1 /&#x22C6; send TS packets (188 bytes) to callback (default) &#x22C6;/
#define TS_PAYLOAD_ONLY 2 /&#x22C6; in case TS_PACKET is set, only send the TS
payload (&#x003C;=184 bytes per packet) to callback &#x22C6;/
#define TS_DECODER 4 /&#x22C6; send stream to built-in decoder (if present) &#x22C6;/
</programlisting>
</section>
<section id="dmx_ts_pes_t">
<title>dmx_ts_pes_t</title>
<para>The structure
</para>
<programlisting>
typedef enum
{
DMX_TS_PES_AUDIO, /&#x22C6; also send packets to audio decoder (if it exists) &#x22C6;/
DMX_TS_PES_VIDEO, /&#x22C6; ... &#x22C6;/
DMX_TS_PES_TELETEXT,
DMX_TS_PES_SUBTITLE,
DMX_TS_PES_PCR,
DMX_TS_PES_OTHER,
} dmx_ts_pes_t;
</programlisting>
<para>describes the PES type for filters which write to a built-in decoder. The correspond (and
should be kept identical) to the types in the demux device.
</para>
<programlisting>
struct dmx_ts_feed_s {
int is_filtering; /&#x22C6; Set to non-zero when filtering in progress &#x22C6;/
struct dmx_demux_s&#x22C6; parent; /&#x22C6; Back-pointer &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
int (&#x22C6;set) (struct dmx_ts_feed_s&#x22C6; feed,
__u16 pid,
size_t callback_length,
size_t circular_buffer_size,
int descramble,
struct timespec timeout);
int (&#x22C6;start_filtering) (struct dmx_ts_feed_s&#x22C6; feed);
int (&#x22C6;stop_filtering) (struct dmx_ts_feed_s&#x22C6; feed);
int (&#x22C6;set_type) (struct dmx_ts_feed_s&#x22C6; feed,
int type,
dmx_ts_pes_t pes_type);
};
typedef struct dmx_ts_feed_s dmx_ts_feed_t;
</programlisting>
<programlisting>
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; PES packet reception (not supported yet) &#x22C6;/
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
typedef struct dmx_pes_filter_s {
struct dmx_pes_s&#x22C6; parent; /&#x22C6; Back-pointer &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
} dmx_pes_filter_t;
</programlisting>
<programlisting>
typedef struct dmx_pes_feed_s {
int is_filtering; /&#x22C6; Set to non-zero when filtering in progress &#x22C6;/
struct dmx_demux_s&#x22C6; parent; /&#x22C6; Back-pointer &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
int (&#x22C6;set) (struct dmx_pes_feed_s&#x22C6; feed,
__u16 pid,
size_t circular_buffer_size,
int descramble,
struct timespec timeout);
int (&#x22C6;start_filtering) (struct dmx_pes_feed_s&#x22C6; feed);
int (&#x22C6;stop_filtering) (struct dmx_pes_feed_s&#x22C6; feed);
int (&#x22C6;allocate_filter) (struct dmx_pes_feed_s&#x22C6; feed,
dmx_pes_filter_t&#x22C6;&#x22C6; filter);
int (&#x22C6;release_filter) (struct dmx_pes_feed_s&#x22C6; feed,
dmx_pes_filter_t&#x22C6; filter);
} dmx_pes_feed_t;
</programlisting>
<programlisting>
typedef struct {
__u8 filter_value [DMX_MAX_FILTER_SIZE];
__u8 filter_mask [DMX_MAX_FILTER_SIZE];
struct dmx_section_feed_s&#x22C6; parent; /&#x22C6; Back-pointer &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
} dmx_section_filter_t;
</programlisting>
<programlisting>
struct dmx_section_feed_s {
int is_filtering; /&#x22C6; Set to non-zero when filtering in progress &#x22C6;/
struct dmx_demux_s&#x22C6; parent; /&#x22C6; Back-pointer &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
int (&#x22C6;set) (struct dmx_section_feed_s&#x22C6; feed,
__u16 pid,
size_t circular_buffer_size,
int descramble,
int check_crc);
int (&#x22C6;allocate_filter) (struct dmx_section_feed_s&#x22C6; feed,
dmx_section_filter_t&#x22C6;&#x22C6; filter);
int (&#x22C6;release_filter) (struct dmx_section_feed_s&#x22C6; feed,
dmx_section_filter_t&#x22C6; filter);
int (&#x22C6;start_filtering) (struct dmx_section_feed_s&#x22C6; feed);
int (&#x22C6;stop_filtering) (struct dmx_section_feed_s&#x22C6; feed);
};
typedef struct dmx_section_feed_s dmx_section_feed_t;
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; Callback functions &#x22C6;/
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
typedef int (&#x22C6;dmx_ts_cb) ( __u8 &#x22C6; buffer1,
size_t buffer1_length,
__u8 &#x22C6; buffer2,
size_t buffer2_length,
dmx_ts_feed_t&#x22C6; source,
dmx_success_t success);
typedef int (&#x22C6;dmx_section_cb) ( __u8 &#x22C6; buffer1,
size_t buffer1_len,
__u8 &#x22C6; buffer2,
size_t buffer2_len,
dmx_section_filter_t &#x22C6; source,
dmx_success_t success);
typedef int (&#x22C6;dmx_pes_cb) ( __u8 &#x22C6; buffer1,
size_t buffer1_len,
__u8 &#x22C6; buffer2,
size_t buffer2_len,
dmx_pes_filter_t&#x22C6; source,
dmx_success_t success);
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; DVB Front-End &#x22C6;/
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
typedef enum {
DMX_OTHER_FE = 0,
DMX_SATELLITE_FE,
DMX_CABLE_FE,
DMX_TERRESTRIAL_FE,
DMX_LVDS_FE,
DMX_ASI_FE, /&#x22C6; DVB-ASI interface &#x22C6;/
DMX_MEMORY_FE
} dmx_frontend_source_t;
typedef struct {
/&#x22C6; The following char&#x22C6; fields point to NULL terminated strings &#x22C6;/
char&#x22C6; id; /&#x22C6; Unique front-end identifier &#x22C6;/
char&#x22C6; vendor; /&#x22C6; Name of the front-end vendor &#x22C6;/
char&#x22C6; model; /&#x22C6; Name of the front-end model &#x22C6;/
struct list_head connectivity_list; /&#x22C6; List of front-ends that can
be connected to a particular
demux &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
dmx_frontend_source_t source;
} dmx_frontend_t;
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6; MPEG-2 TS Demux &#x22C6;/
/&#x22C6;--------------------------------------------------------------------------&#x22C6;/
/&#x22C6;
&#x22C6; Flags OR'ed in the capabilites field of struct dmx_demux_s.
&#x22C6;/
#define DMX_TS_FILTERING 1
#define DMX_PES_FILTERING 2
#define DMX_SECTION_FILTERING 4
#define DMX_MEMORY_BASED_FILTERING 8 /&#x22C6; write() available &#x22C6;/
#define DMX_CRC_CHECKING 16
#define DMX_TS_DESCRAMBLING 32
#define DMX_SECTION_PAYLOAD_DESCRAMBLING 64
#define DMX_MAC_ADDRESS_DESCRAMBLING 128
</programlisting>
</section>
<section id="demux_demux_t">
<title>demux_demux_t</title>
<programlisting>
/&#x22C6;
&#x22C6; DMX_FE_ENTRY(): Casts elements in the list of registered
&#x22C6; front-ends from the generic type struct list_head
&#x22C6; to the type &#x22C6; dmx_frontend_t
&#x22C6;.
&#x22C6;/
#define DMX_FE_ENTRY(list) list_entry(list, dmx_frontend_t, connectivity_list)
struct dmx_demux_s {
/&#x22C6; The following char&#x22C6; fields point to NULL terminated strings &#x22C6;/
char&#x22C6; id; /&#x22C6; Unique demux identifier &#x22C6;/
char&#x22C6; vendor; /&#x22C6; Name of the demux vendor &#x22C6;/
char&#x22C6; model; /&#x22C6; Name of the demux model &#x22C6;/
__u32 capabilities; /&#x22C6; Bitfield of capability flags &#x22C6;/
dmx_frontend_t&#x22C6; frontend; /&#x22C6; Front-end connected to the demux &#x22C6;/
struct list_head reg_list; /&#x22C6; List of registered demuxes &#x22C6;/
void&#x22C6; priv; /&#x22C6; Pointer to private data of the API client &#x22C6;/
int users; /&#x22C6; Number of users &#x22C6;/
int (&#x22C6;open) (struct dmx_demux_s&#x22C6; demux);
int (&#x22C6;close) (struct dmx_demux_s&#x22C6; demux);
int (&#x22C6;write) (struct dmx_demux_s&#x22C6; demux, const char&#x22C6; buf, size_t count);
int (&#x22C6;allocate_ts_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_ts_feed_t&#x22C6;&#x22C6; feed,
dmx_ts_cb callback);
int (&#x22C6;release_ts_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_ts_feed_t&#x22C6; feed);
int (&#x22C6;allocate_pes_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_pes_feed_t&#x22C6;&#x22C6; feed,
dmx_pes_cb callback);
int (&#x22C6;release_pes_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_pes_feed_t&#x22C6; feed);
int (&#x22C6;allocate_section_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_section_feed_t&#x22C6;&#x22C6; feed,
dmx_section_cb callback);
int (&#x22C6;release_section_feed) (struct dmx_demux_s&#x22C6; demux,
dmx_section_feed_t&#x22C6; feed);
int (&#x22C6;descramble_mac_address) (struct dmx_demux_s&#x22C6; demux,
__u8&#x22C6; buffer1,
size_t buffer1_length,
__u8&#x22C6; buffer2,
size_t buffer2_length,
__u16 pid);
int (&#x22C6;descramble_section_payload) (struct dmx_demux_s&#x22C6; demux,
__u8&#x22C6; buffer1,
size_t buffer1_length,
__u8&#x22C6; buffer2, size_t buffer2_length,
__u16 pid);
int (&#x22C6;add_frontend) (struct dmx_demux_s&#x22C6; demux,
dmx_frontend_t&#x22C6; frontend);
int (&#x22C6;remove_frontend) (struct dmx_demux_s&#x22C6; demux,
dmx_frontend_t&#x22C6; frontend);
struct list_head&#x22C6; (&#x22C6;get_frontends) (struct dmx_demux_s&#x22C6; demux);
int (&#x22C6;connect_frontend) (struct dmx_demux_s&#x22C6; demux,
dmx_frontend_t&#x22C6; frontend);
int (&#x22C6;disconnect_frontend) (struct dmx_demux_s&#x22C6; demux);
/&#x22C6; added because js cannot keep track of these himself &#x22C6;/
int (&#x22C6;get_pes_pids) (struct dmx_demux_s&#x22C6; demux, __u16 &#x22C6;pids);
};
typedef struct dmx_demux_s dmx_demux_t;
</programlisting>
</section>
<section id="demux_directory">
<title>Demux directory</title>
<programlisting>
/&#x22C6;
&#x22C6; DMX_DIR_ENTRY(): Casts elements in the list of registered
&#x22C6; demuxes from the generic type struct list_head&#x22C6; to the type dmx_demux_t
&#x22C6;.
&#x22C6;/
#define DMX_DIR_ENTRY(list) list_entry(list, dmx_demux_t, reg_list)
int dmx_register_demux (dmx_demux_t&#x22C6; demux);
int dmx_unregister_demux (dmx_demux_t&#x22C6; demux);
struct list_head&#x22C6; dmx_get_demuxes (void);
</programlisting>
</section></section>
<section id="demux_directory_api">
<title>Demux Directory API</title>
<para>The demux directory is a Linux kernel-wide facility for registering and accessing the
MPEG-2 TS demuxes in the system. Run-time registering and unregistering of demux drivers
is possible using this API.
</para>
<para>All demux drivers in the directory implement the abstract interface dmx_demux_t.
</para>
<section
role="subsection"><title>dmx_register_demux()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function makes a demux driver interface available to the Linux kernel. It is
usually called by the init_module() function of the kernel module that contains
the demux driver. The caller of this function is responsible for allocating
dynamic or static memory for the demux structure and for initializing its fields
before calling this function. The memory allocated for the demux structure
must not be freed before calling dmx_unregister_demux(),</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int dmx_register_demux ( dmx_demux_t &#x22C6;demux )</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux structure.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EEXIST</para>
</entry><entry
align="char">
<para>A demux with the same value of the id field already stored
in the directory.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSPC</para>
</entry><entry
align="char">
<para>No space left in the directory.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>dmx_unregister_demux()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function is called to indicate that the given demux interface is no
longer available. The caller of this function is responsible for freeing the
memory of the demux structure, if it was dynamically allocated before calling
dmx_register_demux(). The cleanup_module() function of the kernel module
that contains the demux driver should call this function. Note that this function
fails if the demux is currently in use, i.e., release_demux() has not been called
for the interface.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int dmx_unregister_demux ( dmx_demux_t &#x22C6;demux )</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux structure which is to be
unregistered.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>ENODEV</para>
</entry><entry
align="char">
<para>The specified demux is not registered in the demux
directory.</para>
</entry>
</row><row><entry
align="char">
<para>EBUSY</para>
</entry><entry
align="char">
<para>The specified demux is currently in use.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>dmx_get_demuxes()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Provides the caller with the list of registered demux interfaces, using the
standard list structure defined in the include file linux/list.h. The include file
demux.h defines the macro DMX_DIR_ENTRY() for converting an element of
the generic type struct list_head* to the type dmx_demux_t*. The caller must
not free the memory of any of the elements obtained via this function call.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>struct list_head &#x22C6;dmx_get_demuxes ()</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>none</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>struct list_head *</para>
</entry><entry
align="char">
<para>A list of demux interfaces, or NULL in the case of an
empty list.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section></section>
<section id="demux_api">
<title>Demux API</title>
<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 the
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 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 Directory for external access. It is not necessary
to implement every function in the demux_t struct, however (for example, a demux interface
might support Section filtering, but not TS or PES filtering). The API client is expected to
check the value of any function pointer before calling the function: the value of NULL means
&#8220;function 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. This is especially important on multi-processor hosts.
</para>
<para>Note that functions called from a bottom half context must not sleep, at least in the 2.2.x
kernels. Even a simple memory allocation 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>
<section id="kdapi_fopen">
<title>open()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function reserves the demux for use by the caller and, if necessary,
initializes the demux. When the demux is no longer needed, the function close()
should be called. It should be possible for multiple clients to access the demux
at the same time. Thus, the function implementation should increment the
demux usage count when open() is called and decrement it when close() is
called.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int open ( demux_t&#x22C6; demux );</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t* demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EUSERS</para>
</entry><entry
align="char">
<para>Maximum usage count reached.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="kdapi_fclose">
<title>close()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function reserves the demux for use by the caller and, if necessary,
initializes the demux. When the demux is no longer needed, the function close()
should be called. It should be possible for multiple clients to access the demux
at the same time. Thus, the function implementation should increment the
demux usage count when open() is called and decrement it when close() is
called.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int close(demux_t&#x22C6; demux);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t* demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENODEV</para>
</entry><entry
align="char">
<para>The demux was not in use.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>
<section id="kdapi_fwrite">
<title>write()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function provides the demux driver with a memory buffer containing TS
packets. Instead of receiving TS packets from the DVB front-end, the demux
driver software will read packets from memory. Any clients of this demux
with active TS, PES or Section filters will receive filtered data via the Demux
callback API (see 0). The function returns when all the data in the buffer has
been consumed by the demux. Demux hardware typically cannot read TS from
memory. If this is the case, memory-based filtering has to be implemented
entirely in software.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int write(demux_t&#x22C6; demux, const char&#x22C6; buf, size_t
count);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t* demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>const char* buf</para>
</entry><entry
align="char">
<para>Pointer to the TS data in kernel-space memory.</para>
</entry>
</row><row><entry
align="char">
<para>size_t length</para>
</entry><entry
align="char">
<para>Length of the TS data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>The command is not implemented.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>allocate_ts_feed()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Allocates a new TS feed, which is used to filter the TS packets carrying a
certain PID. The TS feed normally corresponds to a hardware PID filter on the
demux chip.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int allocate_ts_feed(dmx_demux_t&#x22C6; demux,
dmx_ts_feed_t&#x22C6;&#x22C6; feed, dmx_ts_cb callback);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t* demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_ts_feed_t**
feed</para>
</entry><entry
align="char">
<para>Pointer to the TS feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_ts_cb callback</para>
</entry><entry
align="char">
<para>Pointer to the callback function for passing received TS
packet</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EBUSY</para>
</entry><entry
align="char">
<para>No more TS feeds available.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>The command is not implemented.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>release_ts_feed()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Releases the resources allocated with allocate_ts_feed(). Any filtering in
progress on the TS feed should be stopped before calling this function.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int release_ts_feed(dmx_demux_t&#x22C6; demux,
dmx_ts_feed_t&#x22C6; feed);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t* demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_ts_feed_t* feed</para>
</entry><entry
align="char">
<para>Pointer to the TS feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>allocate_section_feed()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Allocates a new section feed, i.e. a demux resource for filtering and receiving
sections. On platforms with hardware support for section filtering, a section
feed is directly mapped to the demux HW. On other platforms, TS packets are
first PID filtered in hardware and a hardware section filter then emulated in
software. The caller obtains an API pointer of type dmx_section_feed_t as an
out parameter. Using this API the caller can set filtering parameters and start
receiving sections.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int allocate_section_feed(dmx_demux_t&#x22C6; demux,
dmx_section_feed_t &#x22C6;&#x22C6;feed, dmx_section_cb callback);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t *demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_feed_t
**feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_cb
callback</para>
</entry><entry
align="char">
<para>Pointer to the callback function for passing received
sections.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EBUSY</para>
</entry><entry
align="char">
<para>No more section feeds available.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>The command is not implemented.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>release_section_feed()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Releases the resources allocated with allocate_section_feed(), including
allocated filters. Any filtering in progress on the section feed should be stopped
before calling this function.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int release_section_feed(dmx_demux_t&#x22C6; demux,
dmx_section_feed_t &#x22C6;feed);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>demux_t *demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_feed_t
*feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>descramble_mac_address()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function runs a descrambling algorithm on the destination MAC
address field of a DVB Datagram Section, replacing the original address
with its un-encrypted version. Otherwise, the description on the function
descramble_section_payload() applies also to this function.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int descramble_mac_address(dmx_demux_t&#x22C6; demux, __u8
&#x22C6;buffer1, size_t buffer1_length, __u8 &#x22C6;buffer2,
size_t buffer2_length, __u16 pid);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t
*demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>__u8 *buffer1</para>
</entry><entry
align="char">
<para>Pointer to the first byte of the section.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer1_length</para>
</entry><entry
align="char">
<para>Length of the section data, including headers and CRC,
in buffer1.</para>
</entry>
</row><row><entry
align="char">
<para>__u8* buffer2</para>
</entry><entry
align="char">
<para>Pointer to the tail of the section data, or NULL. The
pointer has a non-NULL value if the section wraps past
the end of a circular buffer.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer2_length</para>
</entry><entry
align="char">
<para>Length of the section data, including headers and CRC,
in buffer2.</para>
</entry>
</row><row><entry
align="char">
<para>__u16 pid</para>
</entry><entry
align="char">
<para>The PID on which the section was received. Useful
for obtaining the descrambling key, e.g. from a DVB
Common Access facility.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>No descrambling facility available.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>descramble_section_payload()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function runs a descrambling algorithm on the payload of a DVB
Datagram Section, replacing the original payload with its un-encrypted
version. The function will be called from the demux API implementation;
the API client need not call this function directly. Section-level scrambling
algorithms are currently standardized only for DVB-RCC (return channel
over 2-directional cable TV network) systems. For all other DVB networks,
encryption schemes are likely to be proprietary to each data broadcaster. Thus,
it is expected that this function pointer will have the value of NULL (i.e.,
function not available) in most demux API implementations. Nevertheless, it
should be possible to use the function pointer as a hook for dynamically adding
a &#8220;plug-in&#8221; descrambling facility to a demux driver.</para>
</entry>
</row><row><entry
align="char">
<para>While this function is not needed with hardware-based section descrambling,
the descramble_section_payload function pointer can be used to override the
default hardware-based descrambling algorithm: if the function pointer has a
non-NULL value, the corresponding function should be used instead of any
descrambling hardware.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int descramble_section_payload(dmx_demux_t&#x22C6; demux,
__u8 &#x22C6;buffer1, size_t buffer1_length, __u8 &#x22C6;buffer2,
size_t buffer2_length, __u16 pid);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t
*demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>__u8 *buffer1</para>
</entry><entry
align="char">
<para>Pointer to the first byte of the section.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer1_length</para>
</entry><entry
align="char">
<para>Length of the section data, including headers and CRC,
in buffer1.</para>
</entry>
</row><row><entry
align="char">
<para>__u8 *buffer2</para>
</entry><entry
align="char">
<para>Pointer to the tail of the section data, or NULL. The
pointer has a non-NULL value if the section wraps past
the end of a circular buffer.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer2_length</para>
</entry><entry
align="char">
<para>Length of the section data, including headers and CRC,
in buffer2.</para>
</entry>
</row><row><entry
align="char">
<para>__u16 pid</para>
</entry><entry
align="char">
<para>The PID on which the section was received. Useful
for obtaining the descrambling key, e.g. from a DVB
Common Access facility.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>No descrambling facility available.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>add_frontend()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Registers a connectivity between a demux and a front-end, i.e., indicates that
the demux can be connected via a call to connect_frontend() to use the given
front-end as a TS source. The client of this function has to allocate dynamic or
static memory for the frontend structure and initialize its fields before calling
this function. This function is normally called during the driver initialization.
The caller must not free the memory of the frontend struct before successfully
calling remove_frontend().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int add_frontend(dmx_demux_t &#x22C6;demux, dmx_frontend_t
&#x22C6;frontend);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_frontend_t*
frontend</para>
</entry><entry
align="char">
<para>Pointer to the front-end instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EEXIST</para>
</entry><entry
align="char">
<para>A front-end with the same value of the id field already
registered.</para>
</entry>
</row><row><entry
align="char">
<para>-EINUSE</para>
</entry><entry
align="char">
<para>The demux is in use.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOMEM</para>
</entry><entry
align="char">
<para>No more front-ends can be added.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>remove_frontend()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Indicates that the given front-end, registered by a call to add_frontend(), can
no longer be connected as a TS source by this demux. The function should be
called when a front-end driver or a demux driver is removed from the system.
If the front-end is in use, the function fails with the return value of -EBUSY.
After successfully calling this function, the caller can free the memory of
the frontend struct if it was dynamically allocated before the add_frontend()
operation.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int remove_frontend(dmx_demux_t&#x22C6; demux,
dmx_frontend_t&#x22C6; frontend);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_frontend_t*
frontend</para>
</entry><entry
align="char">
<para>Pointer to the front-end instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row><row><entry
align="char">
<para>-EBUSY</para>
</entry><entry
align="char">
<para>The front-end is in use, i.e. a call to connect_frontend()
has not been followed by a call to disconnect_frontend().</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>get_frontends()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Provides the APIs of the front-ends that have been registered for this demux.
Any of the front-ends obtained with this call can be used as a parameter for
connect_frontend().</para>
</entry>
</row><row><entry
align="char">
<para>The include file demux.h contains the macro DMX_FE_ENTRY() for
converting an element of the generic type struct list_head* to the type
dmx_frontend_t*. The caller must not free the memory of any of the elements
obtained via this function call.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>struct list_head&#x22C6; get_frontends(dmx_demux_t&#x22C6; demux);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*</para>
</entry><entry
align="char">
<para>A list of front-end interfaces, or NULL in the case of an
empty list.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>connect_frontend()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Connects the TS output of the front-end to the input of the demux. A demux
can only be connected to a front-end registered to the demux with the function
add_frontend().</para>
</entry>
</row><row><entry
align="char">
<para>It may or may not be possible to connect multiple demuxes to the same
front-end, depending on the capabilities of the HW platform. When not used,
the front-end should be released by calling disconnect_frontend().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int connect_frontend(dmx_demux_t&#x22C6; demux,
dmx_frontend_t&#x22C6; frontend);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_frontend_t*
frontend</para>
</entry><entry
align="char">
<para>Pointer to the front-end instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row><row><entry
align="char">
<para>-EBUSY</para>
</entry><entry
align="char">
<para>The front-end is in use.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>disconnect_frontend()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Disconnects the demux and a front-end previously connected by a
connect_frontend() call.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int disconnect_frontend(dmx_demux_t&#x22C6; demux);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_demux_t*
demux</para>
</entry><entry
align="char">
<para>Pointer to the demux API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section></section>
<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 APIs, these API 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>
<section
role="subsection"><title>dmx_ts_cb()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function, provided by the client of the demux API, is called from the
demux code. The function is only called when filtering on this TS feed has
been enabled using the start_filtering() function.</para>
</entry>
</row><row><entry
align="char">
<para>Any TS packets that match the filter settings are copied to a circular buffer. The
filtered TS packets are delivered to the client using this callback function. The
size of the circular buffer is controlled by the circular_buffer_size parameter
of the set() function in the TS Feed API. It is expected that the buffer1 and
buffer2 callback parameters point to addresses within the circular buffer, but
other implementations are also possible. Note that the called party should not
try to free the memory the buffer1 and buffer2 parameters point to.</para>
</entry>
</row><row><entry
align="char">
<para>When this function is called, the buffer1 parameter typically points to the
start of the first undelivered TS packet within a circular buffer. The buffer2
buffer parameter is normally NULL, except when the received TS packets have
crossed the last address of the circular buffer and &#8221;wrapped&#8221; to the beginning
of the buffer. In the latter case the buffer1 parameter would contain an address
within the circular buffer, while the buffer2 parameter would contain the first
address of the circular buffer.</para>
</entry>
</row><row><entry
align="char">
<para>The number of bytes delivered with this function (i.e. buffer1_length +
buffer2_length) is usually equal to the value of callback_length parameter
given in the set() function, with one exception: if a timeout occurs before
receiving callback_length bytes of TS data, any undelivered packets are
immediately delivered to the client by calling this function. The timeout
duration is controlled by the set() function in the TS Feed API.</para>
</entry>
</row><row><entry
align="char">
<para>If a TS packet is received with errors that could not be fixed by the TS-level
forward error correction (FEC), the Transport_error_indicator flag of the TS
packet header should be set. The TS packet should not be discarded, as
the error can possibly be corrected by a higher layer protocol. If the called
party is slow in processing the callback, it is possible that the circular buffer
eventually fills up. If this happens, the demux driver should discard any TS
packets received while the buffer is full. The error should be indicated to the
client on the next callback by setting the success parameter to the value of
DMX_OVERRUN_ERROR.</para>
</entry>
</row><row><entry
align="char">
<para>The type of data returned to the callback can be selected by the new
function int (*set_type) (struct dmx_ts_feed_s* feed, int type, dmx_ts_pes_t
pes_type) which is part of the dmx_ts_feed_s struct (also cf. to the
include file ost/demux.h) The type parameter decides if the raw TS packet
(TS_PACKET) or just the payload (TS_PACKET&#8212;TS_PAYLOAD_ONLY)
should be returned. If additionally the TS_DECODER bit is set the stream
will also be sent to the hardware MPEG decoder. In this case, the second
flag decides as what kind of data the stream should be interpreted. The
possible choices are one of DMX_TS_PES_AUDIO, DMX_TS_PES_VIDEO,
DMX_TS_PES_TELETEXT, DMX_TS_PES_SUBTITLE,
DMX_TS_PES_PCR, or DMX_TS_PES_OTHER.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int dmx_ts_cb(__u8&#x22C6; buffer1, size_t buffer1_length,
__u8&#x22C6; buffer2, size_t buffer2_length, dmx_ts_feed_t&#x22C6;
source, dmx_success_t success);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>__u8* buffer1</para>
</entry><entry
align="char">
<para>Pointer to the start of the filtered TS packets.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer1_length</para>
</entry><entry
align="char">
<para>Length of the TS data in buffer1.</para>
</entry>
</row><row><entry
align="char">
<para>__u8* buffer2</para>
</entry><entry
align="char">
<para>Pointer to the tail of the filtered TS packets, or NULL.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer2_length</para>
</entry><entry
align="char">
<para>Length of the TS data in buffer2.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_ts_feed_t*
source</para>
</entry><entry
align="char">
<para>Indicates which TS feed is the source of the callback.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_success_t
success</para>
</entry><entry
align="char">
<para>Indicates if there was an error in TS reception.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>Continue filtering.</para>
</entry>
</row><row><entry
align="char">
<para>-1</para>
</entry><entry
align="char">
<para>Stop filtering - has the same effect as a call to
stop_filtering() on the TS Feed API.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>dmx_section_cb()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function, provided by the client of the demux API, is called from the
demux code. The function is only called when filtering of sections has been
enabled using the function start_filtering() of the section feed API. When the
demux driver has received a complete section that matches at least one section
filter, the client is notified via this callback function. Normally this function is
called for each received section; however, it is also possible to deliver multiple
sections with one callback, for example when the system load is high. If an
error occurs while receiving a section, this function should be called with
the corresponding error type set in the success field, whether or not there is
data to deliver. The Section Feed implementation should maintain a circular
buffer for received sections. However, this is not necessary if the Section Feed
API is implemented as a client of the TS Feed API, because the TS Feed
implementation then buffers the received data. The size of the circular buffer
can be configured using the set() function in the Section Feed API. If there
is no room in the circular buffer when a new section is received, the section
must be discarded. If this happens, the value of the success parameter should
be DMX_OVERRUN_ERROR on the next callback.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int dmx_section_cb(__u8&#x22C6; buffer1, size_t
buffer1_length, __u8&#x22C6; buffer2, size_t
buffer2_length, dmx_section_filter_t&#x22C6; source,
dmx_success_t success);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>__u8* buffer1</para>
</entry><entry
align="char">
<para>Pointer to the start of the filtered section, e.g. within the
circular buffer of the demux driver.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer1_length</para>
</entry><entry
align="char">
<para>Length of the filtered section data in buffer1, including
headers and CRC.</para>
</entry>
</row><row><entry
align="char">
<para>__u8* buffer2</para>
</entry><entry
align="char">
<para>Pointer to the tail of the filtered section data, or NULL.
Useful to handle the wrapping of a circular buffer.</para>
</entry>
</row><row><entry
align="char">
<para>size_t buffer2_length</para>
</entry><entry
align="char">
<para>Length of the filtered section data in buffer2, including
headers and CRC.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_filter_t*
filter</para>
</entry><entry
align="char">
<para>Indicates the filter that triggered the callback.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_success_t
success</para>
</entry><entry
align="char">
<para>Indicates if there was an error in section reception.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>Continue filtering.</para>
</entry>
</row><row><entry
align="char">
<para>-1</para>
</entry><entry
align="char">
<para>Stop filtering - has the same effect as a call to
stop_filtering() on the Section Feed API.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section></section>
<section id="ts_feed_api">
<title>TS Feed API</title>
<para>A TS feed is typically mapped to a hardware PID filter on the demux chip.
Using this API, the client can set the filtering properties to start/stop filtering TS
packets on a particular TS feed. The API is defined as an abstract interface of the type
dmx_ts_feed_t.
</para>
<para>The functions that implement the interface should be defined static or module private. The
client can get the handle of a TS feed API by calling the function allocate_ts_feed() in the
demux API.
</para>
<section
role="subsection"><title>set()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function sets the parameters of a TS feed. Any filtering in progress on the
TS feed must be stopped before calling this function.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int set ( dmx_ts_feed_t&#x22C6; feed, __u16 pid, size_t
callback_length, size_t circular_buffer_size, int
descramble, struct timespec timeout);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_ts_feed_t* feed</para>
</entry><entry
align="char">
<para>Pointer to the TS feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>__u16 pid</para>
</entry><entry
align="char">
<para>PID value to filter. Only the TS packets carrying the
specified PID will be passed to the API client.</para>
</entry>
</row><row><entry
align="char">
<para>size_t
callback_length</para>
</entry><entry
align="char">
<para>Number of bytes to deliver with each call to the
dmx_ts_cb() callback function. The value of this
parameter should be a multiple of 188.</para>
</entry>
</row><row><entry
align="char">
<para>size_t
circular_buffer_size</para>
</entry><entry
align="char">
<para>Size of the circular buffer for the filtered TS packets.</para>
</entry>
</row><row><entry
align="char">
<para>int descramble</para>
</entry><entry
align="char">
<para>If non-zero, descramble the filtered TS packets.</para>
</entry>
</row><row><entry
align="char">
<para>struct timespec
timeout</para>
</entry><entry
align="char">
<para>Maximum time to wait before delivering received TS
packets to the client.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOMEM</para>
</entry><entry
align="char">
<para>Not enough memory for the requested buffer size.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>No descrambling facility available for TS.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>start_filtering()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Starts filtering TS packets on this TS feed, according to its settings. The PID
value to filter can be set by the API client. All matching TS packets are
delivered asynchronously to the client, using the callback function registered
with allocate_ts_feed().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int start_filtering(dmx_ts_feed_t&#x22C6; feed);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_ts_feed_t* feed</para>
</entry><entry
align="char">
<para>Pointer to the TS feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>stop_filtering()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Stops filtering TS packets on this TS feed.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int stop_filtering(dmx_ts_feed_t&#x22C6; feed);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_ts_feed_t* feed</para>
</entry><entry
align="char">
<para>Pointer to the TS feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section></section>
<section id="section_feed_api">
<title>Section Feed API</title>
<para>A section feed is a resource consisting of a PID filter and a set of section filters. Using this
API, the client can set the properties of a section feed and to start/stop filtering. The API is
defined as an abstract interface of the type dmx_section_feed_t. The functions that implement
the interface should be defined static or module private. The client can get the handle of
a section feed API by calling the function allocate_section_feed() in the demux
API.
</para>
<para>On demux platforms that provide section filtering in hardware, the Section Feed API
implementation provides a software wrapper for the demux hardware. Other platforms may
support only PID filtering in hardware, requiring that TS packets are converted to sections in
software. In the latter case the Section Feed API implementation can be a client of the TS
Feed API.
</para>
</section>
<section id="kdapi_set">
<title>set()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function sets the parameters of a section feed. Any filtering in progress on
the section feed must be stopped before calling this function. If descrambling
is enabled, the payload_scrambling_control and address_scrambling_control
fields of received DVB datagram sections should be observed. If either one is
non-zero, the section should be descrambled either in hardware or using the
functions descramble_mac_address() and descramble_section_payload() of the
demux API. Note that according to the MPEG-2 Systems specification, only
the payloads of private sections can be scrambled while the rest of the section
data must be sent in the clear.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int set(dmx_section_feed_t&#x22C6; feed, __u16 pid, size_t
circular_buffer_size, int descramble, int
check_crc);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_section_feed_t*
feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>__u16 pid</para>
</entry><entry
align="char">
<para>PID value to filter; only the TS packets carrying the
specified PID will be accepted.</para>
</entry>
</row><row><entry
align="char">
<para>size_t
circular_buffer_size</para>
</entry><entry
align="char">
<para>Size of the circular buffer for filtered sections.</para>
</entry>
</row><row><entry
align="char">
<para>int descramble</para>
</entry><entry
align="char">
<para>If non-zero, descramble any sections that are scrambled.</para>
</entry>
</row><row><entry
align="char">
<para>int check_crc</para>
</entry><entry
align="char">
<para>If non-zero, check the CRC values of filtered sections.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOMEM</para>
</entry><entry
align="char">
<para>Not enough memory for the requested buffer size.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSYS</para>
</entry><entry
align="char">
<para>No descrambling facility available for sections.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameters.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>allocate_filter()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function is used to allocate a section filter on the demux. It should only be
called when no filtering is in progress on this section feed. If a filter cannot be
allocated, the function fails with -ENOSPC. See in section ?? for the format of
the section filter.</para>
</entry>
</row><row><entry
align="char">
<para>The bitfields filter_mask and filter_value should only be modified when no
filtering is in progress on this section feed. filter_mask controls which bits of
filter_value are compared with the section headers/payload. On a binary value
of 1 in filter_mask, the corresponding bits are compared. The filter only accepts
sections that are equal to filter_value in all the tested bit positions. Any changes
to the values of filter_mask and filter_value are guaranteed to take effect only
when the start_filtering() function is called next time. The parent pointer in
the struct is initialized by the API implementation to the value of the feed
parameter. The priv pointer is not used by the API implementation, and can
thus be freely utilized by the caller of this function. Any data pointed to by the
priv pointer is available to the recipient of the dmx_section_cb() function call.</para>
</entry>
</row><row><entry
align="char">
<para>While the maximum section filter length (DMX_MAX_FILTER_SIZE) is
currently set at 16 bytes, hardware filters of that size are not available on all
platforms. Therefore, section filtering will often take place first in hardware,
followed by filtering in software for the header bytes that were not covered
by a hardware filter. The filter_mask field can be checked to determine how
many bytes of the section filter are actually used, and if the hardware filter will
suffice. Additionally, software-only section filters can optionally be allocated
to clients when all hardware section filters are in use. Note that on most demux
hardware it is not possible to filter on the section_length field of the section
header &#8211; thus this field is ignored, even though it is included in filter_value and
filter_mask fields.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int allocate_filter(dmx_section_feed_t&#x22C6; feed,
dmx_section_filter_t&#x22C6;&#x22C6; filter);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_section_feed_t*
feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_filter_t**
filter</para>
</entry><entry
align="char">
<para>Pointer to the allocated filter.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENOSPC</para>
</entry><entry
align="char">
<para>No filters of given type and length available.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameters.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>release_filter()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>This function releases all the resources of a previously allocated section filter.
The function should not be called while filtering is in progress on this section
feed. After calling this function, the caller should not try to dereference the
filter pointer.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int release_filter ( dmx_section_feed_t&#x22C6; feed,
dmx_section_filter_t&#x22C6; filter);</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_section_feed_t*
feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row><row><entry
align="char">
<para>dmx_section_filter_t*
filter</para>
</entry><entry
align="char">
<para>I/O Pointer to the instance data of a section filter.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-ENODEV</para>
</entry><entry
align="char">
<para>No such filter allocated.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>start_filtering()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Starts filtering sections on this section feed, according to its settings. Sections
are first filtered based on their PID and then matched with the section
filters allocated for this feed. If the section matches the PID filter and
at least one section filter, it is delivered to the API client. The section
is delivered asynchronously using the callback function registered with
allocate_section_feed().</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int start_filtering ( dmx_section_feed_t&#x22C6; feed );</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_section_feed_t*
feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section><section
role="subsection"><title>stop_filtering()</title>
<para>DESCRIPTION
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>Stops filtering sections on this section feed. Note that any changes to the
filtering parameters (filter_value, filter_mask, etc.) should only be made when
filtering is stopped.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>SYNOPSIS
</para>
<informaltable><tgroup cols="1"><tbody><row><entry
align="char">
<para>int stop_filtering ( dmx_section_feed_t&#x22C6; feed );</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>PARAMETERS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>dmx_section_feed_t*
feed</para>
</entry><entry
align="char">
<para>Pointer to the section feed API and instance data.</para>
</entry>
</row></tbody></tgroup></informaltable>
<para>RETURNS
</para>
<informaltable><tgroup cols="2"><tbody><row><entry
align="char">
<para>0</para>
</entry><entry
align="char">
<para>The function was completed without errors.</para>
</entry>
</row><row><entry
align="char">
<para>-EINVAL</para>
</entry><entry
align="char">
<para>Bad parameter.</para>
</entry>
</row></tbody></tgroup></informaltable>
</section>