2. Digital TV (DVB) devices

Digital TV devices are implemented by several different drivers:

• A bridge driver that is responsible to talk with the bus where the other devices are connected (PCI, USB, SPI), bind to the other drivers and implement the digital demux logic (either in software or in hardware);
• Frontend drivers that are usually implemented as two separate drivers:
  • A tuner driver that implements the logic with commands the part of the hardware with is reponsible to tune into a digital TV transponder or physical channel. The output of a tuner is usually a baseband or Intermediate Frequency (IF) signal;
  • A demodulator driver (a.k.a “demod”) that implements the logic with commands the digital TV decoding hardware. The output of a demod is a digital stream, with multiple audio, video and data channels typically multiplexed using MPEG Transport Stream [1].

On most hardware, the frontend drivers talk with the bridge driver using an I2C bus.

[1]	Some standards use TCP/IP for multiplexing data, like DVB-H (an abandoned standard, not used anymore) and ATSC version 3.0 current proposals. Currently, the DVB subsystem doesn’t implement those standards.

3. Digital TV Common functions

unsigned int intlog2(u32 value)

computes log2 of a value; the result is shifted left by 24 bits

Parameters

u32 value

The value (must be != 0)

Description

to use rational values you can use the following method:

intlog2(value) = intlog2(value * 2^x) - x * 2^24

Some usecase examples:

intlog2(8) will give 3 << 24 = 3 * 2^24

intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24

intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24

Return

log2(value) * 2^24

unsigned int intlog10(u32 value)

computes log10 of a value; the result is shifted left by 24 bits

Parameters

u32 value

The value (must be != 0)

Description

to use rational values you can use the following method:

intlog10(value) = intlog10(value * 10^x) - x * 2^24

An usecase example:

intlog10(1000) will give 3 << 24 = 3 * 2^24

due to the implementation intlog10(1000) might be not exactly 3 * 2^24

look at intlog2 for similar examples

Return

log10(value) * 2^24

struct dvb_adapter

represents a Digital TV adapter using Linux DVB API

Definition

struct dvb_adapter {
  int num;
  struct list_head list_head;
  struct list_head device_list;
  const char * name;
  u8 proposed_mac;
  void * priv;
  struct device * device;
  struct module * module;
  int mfe_shared;
  struct dvb_device * mfe_dvbdev;
  struct mutex mfe_lock;
#if defined(CONFIG_MEDIA_CONTROLLER_DVB
  struct media_device * mdev;
  struct media_entity * conn;
  struct media_pad * conn_pads;
#endif
};

Members

num

Number of the adapter

list_head

List with the DVB adapters

device_list

List with the DVB devices

name

Name of the adapter

proposed_mac

proposed MAC address for the adapter

priv

private data

device

pointer to struct device

module

pointer to struct module

mfe_shared

mfe shared: indicates mutually exclusive frontends Thie usage of this flag is currently deprecated

mfe_dvbdev

Frontend device in use, in the case of MFE

mfe_lock

Lock to prevent using the other frontends when MFE is used.

mdev

pointer to struct media_device, used when the media controller is used.

conn

RF connector. Used only if the device has no separate tuner.

conn_pads

pointer to struct media_pad associated with conn;

struct dvb_device

represents a DVB device node

Definition

struct dvb_device {
  struct list_head list_head;
  const struct file_operations * fops;
  struct dvb_adapter * adapter;
  int type;
  int minor;
  u32 id;
  int readers;
  int writers;
  int users;
  wait_queue_head_t wait_queue;
  int (* kernel_ioctl) (struct file *file, unsigned int cmd, void *arg);
#if defined(CONFIG_MEDIA_CONTROLLER_DVB
  const char * name;
  struct media_intf_devnode * intf_devnode;
  unsigned tsout_num_entities;
  struct media_entity * entity;
  struct media_entity * tsout_entity;
  struct media_pad * pads;
  struct media_pad * tsout_pads;
#endif
  void * priv;
};

Members

list_head

List head with all DVB devices

fops

pointer to struct file_operations

adapter

pointer to the adapter that holds this device node

type

type of the device: DVB_DEVICE_SEC, DVB_DEVICE_FRONTEND, DVB_DEVICE_DEMUX, DVB_DEVICE_DVR, DVB_DEVICE_CA, DVB_DEVICE_NET

minor

devnode minor number. Major number is always DVB_MAJOR.

id

device ID number, inside the adapter

readers

Initialized by the caller. Each call to open() in Read Only mode decreases this counter by one.

writers

Initialized by the caller. Each call to open() in Read/Write mode decreases this counter by one.

users

Initialized by the caller. Each call to open() in any mode decreases this counter by one.

wait_queue

wait queue, used to wait for certain events inside one of the DVB API callers

kernel_ioctl

callback function used to handle ioctl calls from userspace.

name

Name to be used for the device at the Media Controller

intf_devnode

Pointer to media_intf_devnode. Used by the dvbdev core to store the MC device node interface

tsout_num_entities

Number of Transport Stream output entities

entity

pointer to struct media_entity associated with the device node

tsout_entity

array with MC entities associated to each TS output node

pads

pointer to struct media_pad associated with entity;

tsout_pads

array with the source pads for each tsout_entity

priv

private data

Description

This structure is used by the DVB core (frontend, CA, net, demux) in order to create the device nodes. Usually, driver should not initialize this struct diretly.

int dvb_register_adapter(struct dvb_adapter * adap, const char * name, struct module * module, struct device * device, short * adapter_nums)

Registers a new DVB adapter

Parameters

struct dvb_adapter * adap

pointer to struct dvb_adapter

const char * name

Adapter’s name

struct module * module

initialized with THIS_MODULE at the caller

struct device * device

pointer to struct device that corresponds to the device driver

short * adapter_nums

Array with a list of the numbers for dvb_register_adapter; to select among them. Typically, initialized with: DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nums)

int dvb_unregister_adapter(struct dvb_adapter * adap)

Unregisters a DVB adapter

Parameters

struct dvb_adapter * adap

pointer to struct dvb_adapter

int dvb_register_device(struct dvb_adapter * adap, struct dvb_device ** pdvbdev, const struct dvb_device * template, void * priv, int type, int demux_sink_pads)

Registers a new DVB device

Parameters

struct dvb_adapter * adap

pointer to struct dvb_adapter

struct dvb_device ** pdvbdev

pointer to the place where the new struct dvb_device will be stored

const struct dvb_device * template

Template used to create pdvbdev;

void * priv

private data

int type

type of the device: DVB_DEVICE_SEC, DVB_DEVICE_FRONTEND, DVB_DEVICE_DEMUX, DVB_DEVICE_DVR, DVB_DEVICE_CA, DVB_DEVICE_NET

int demux_sink_pads

Number of demux outputs, to be used to create the TS outputs via the Media Controller.

void dvb_remove_device(struct dvb_device * dvbdev)

Remove a registered DVB device

Parameters

struct dvb_device * dvbdev

pointer to struct dvb_device

Description

This does not free memory. To do that, call dvb_free_device().

void dvb_free_device(struct dvb_device * dvbdev)

Free memory occupied by a DVB device.

Parameters

struct dvb_device * dvbdev

pointer to struct dvb_device

Description

Call dvb_unregister_device() before calling this function.

void dvb_unregister_device(struct dvb_device * dvbdev)

Unregisters a DVB device

Parameters

struct dvb_device * dvbdev

pointer to struct dvb_device

Description

This is a combination of dvb_remove_device() and dvb_free_device(). Using this function is usually a mistake, and is often an indicator for a use-after-free bug (when a userspace process keeps a file handle to a detached device).

int dvb_create_media_graph(struct dvb_adapter * adap, bool create_rf_connector)

Creates media graph for the Digital TV part of the device.

Parameters

struct dvb_adapter * adap

pointer to struct dvb_adapter

bool create_rf_connector

if true, it creates the RF connector too

Description

This function checks all DVB-related functions at the media controller entities and creates the needed links for the media graph. It is capable of working with multiple tuners or multiple frontends, but it won’t create links if the device has multiple tuners and multiple frontends or if the device has multiple muxes. In such case, the caller driver should manually create the remaining links.

4. Digital TV Ring buffer

Those routines implement ring buffers used to handle digital TV data and copy it from/to userspace.

Note

1. For performance reasons read and write routines don’t check buffer sizes and/or number of bytes free/available. This has to be done before these routines are called. For example:

/* write @buflen: bytes */
free = dvb_ringbuffer_free(rbuf);
if (free >= buflen)
        count = dvb_ringbuffer_write(rbuf, buffer, buflen);
else
        /* do something */

/* read min. 1000, max. @bufsize: bytes */
avail = dvb_ringbuffer_avail(rbuf);
if (avail >= 1000)
        count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
else
        /* do something */

2. If there is exactly one reader and one writer, there is no need to lock read or write operations. Two or more readers must be locked against each other. Flushing the buffer counts as a read operation. Resetting the buffer counts as a read and write operation. Two or more writers must be locked against each other.

struct dvb_ringbuffer

Describes a ring buffer used at DVB framework

Definition

struct dvb_ringbuffer {
  u8 * data;
  ssize_t size;
  ssize_t pread;
  ssize_t pwrite;
  int error;
  wait_queue_head_t queue;
  spinlock_t lock;
};

Members

data

Area were the ringbuffer data is written

size

size of the ringbuffer

pread

next position to read

pwrite

next position to write

error

used by ringbuffer clients to indicate that an error happened.

queue

Wait queue used by ringbuffer clients to indicate when buffer was filled

lock

Spinlock used to protect the ringbuffer

void dvb_ringbuffer_init(struct dvb_ringbuffer * rbuf, void * data, size_t len)

initialize ring buffer, lock and queue

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

void * data

pointer to the buffer where the data will be stored

size_t len

bytes from ring buffer into buf

int dvb_ringbuffer_empty(struct dvb_ringbuffer * rbuf)

test whether buffer is empty

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer * rbuf)

returns the number of free bytes in the buffer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

Return

number of free bytes in the buffer

ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer * rbuf)

returns the number of bytes waiting in the buffer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

Return

number of bytes waiting in the buffer

void dvb_ringbuffer_reset(struct dvb_ringbuffer * rbuf)

resets the ringbuffer to initial state

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

Description

Resets the read and write pointers to zero and flush the buffer.

This counts as a read and write operation

void dvb_ringbuffer_flush(struct dvb_ringbuffer * rbuf)

flush buffer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer * rbuf)

flush buffer protected by spinlock and wake-up waiting task(s)

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

DVB_RINGBUFFER_PEEK(rbuf, offs)

peek at byte offs in the buffer

Parameters

rbuf

pointer to struct dvb_ringbuffer

offs

offset inside the ringbuffer

DVB_RINGBUFFER_SKIP(rbuf, num)

advance read ptr by num bytes

Parameters

rbuf

pointer to struct dvb_ringbuffer

num

number of bytes to advance

ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer * rbuf, u8 __user * buf, size_t len)

Reads a buffer into a user pointer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

u8 __user * buf

pointer to the buffer where the data will be stored

size_t len

bytes from ring buffer into buf

Description

This variant assumes that the buffer is a memory at the userspace. So, it will internally call copy_to_user().

Return

number of bytes transferred or -EFAULT

void dvb_ringbuffer_read(struct dvb_ringbuffer * rbuf, u8 * buf, size_t len)

Reads a buffer into a pointer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

u8 * buf

pointer to the buffer where the data will be stored

size_t len

bytes from ring buffer into buf

Description

This variant assumes that the buffer is a memory at the Kernel space

Return

number of bytes transferred or -EFAULT

DVB_RINGBUFFER_WRITE_BYTE(rbuf, byte)

write single byte to ring buffer

Parameters

rbuf

pointer to struct dvb_ringbuffer

byte

byte to write

ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer * rbuf, const u8 * buf, size_t len)

Writes a buffer into the ringbuffer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

const u8 * buf

pointer to the buffer where the data will be read

size_t len

bytes from ring buffer into buf

Description

This variant assumes that the buffer is a memory at the Kernel space

Return

number of bytes transferred or -EFAULT

ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer * rbuf, const u8 __user * buf, size_t len)

Writes a buffer received via a user pointer

Parameters

struct dvb_ringbuffer * rbuf

pointer to struct dvb_ringbuffer

const u8 __user * buf

pointer to the buffer where the data will be read

size_t len

bytes from ring buffer into buf

Description

This variant assumes that the buffer is a memory at the userspace. So, it will internally call copy_from_user().

Return

number of bytes transferred or -EFAULT

ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer * rbuf, u8 * buf, size_t len)

Write a packet into the ringbuffer.

Parameters

struct dvb_ringbuffer * rbuf

Ringbuffer to write to.

u8 * buf

Buffer to write.

size_t len

Length of buffer (currently limited to 65535 bytes max).

Return

Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.

ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer * rbuf, size_t idx, int offset, u8 __user * buf, size_t len)

Read from a packet in the ringbuffer.

Parameters

struct dvb_ringbuffer * rbuf

Ringbuffer concerned.

size_t idx

Packet index as returned by dvb_ringbuffer_pkt_next().

int offset

Offset into packet to read from.

u8 __user * buf

Destination buffer for data.

size_t len

Size of destination buffer.

Return

Number of bytes read, or -EFAULT.

Note

unlike dvb_ringbuffer_read(), this does NOT update the read pointer in the ringbuffer. You must use dvb_ringbuffer_pkt_dispose() to mark a packet as no longer required.

ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer * rbuf, size_t idx, int offset, u8 * buf, size_t len)

Read from a packet in the ringbuffer.

Parameters

struct dvb_ringbuffer * rbuf

Ringbuffer concerned.

size_t idx

Packet index as returned by dvb_ringbuffer_pkt_next().

int offset

Offset into packet to read from.

u8 * buf

Destination buffer for data.

size_t len

Size of destination buffer.

Note

unlike dvb_ringbuffer_read_user(), this DOES update the read pointer in the ringbuffer.

Return

Number of bytes read, or -EFAULT.

void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer * rbuf, size_t idx)

Dispose of a packet in the ring buffer.

Parameters

struct dvb_ringbuffer * rbuf

Ring buffer concerned.

size_t idx

Packet index as returned by dvb_ringbuffer_pkt_next().

ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer * rbuf, size_t idx, size_t * pktlen)

Get the index of the next packet in a ringbuffer.

Parameters

struct dvb_ringbuffer * rbuf

Ringbuffer concerned.

size_t idx

Previous packet index, or -1 to return the first packet index.

size_t * pktlen

On success, will be updated to contain the length of the packet in bytes. returns Packet index (if >=0), or -1 if no packets available.

5. Digital TV Frontend kABI

5.1. Digital TV Frontend

The Digital TV Frontend kABI defines a driver-internal interface for registering low-level, hardware specific driver to a hardware independent frontend layer. It is only of interest for Digital TV device driver writers. The header file for this API is named dvb_frontend.h and located in drivers/media/dvb-core.

5.1.1. Demodulator driver

The demodulator driver is responsible to talk with the decoding part of the hardware. Such driver should implement dvb_frontend_ops, with tells what type of digital TV standards are supported, and points to a series of functions that allow the DVB core to command the hardware via the code under drivers/media/dvb-core/dvb_frontend.c.

A typical example of such struct in a driver foo is:

static struct dvb_frontend_ops foo_ops = {
        .delsys = { SYS_DVBT, SYS_DVBT2, SYS_DVBC_ANNEX_A },
        .info = {
                .name   = "foo DVB-T/T2/C driver",
                .caps = FE_CAN_FEC_1_2 |
                        FE_CAN_FEC_2_3 |
                        FE_CAN_FEC_3_4 |
                        FE_CAN_FEC_5_6 |
                        FE_CAN_FEC_7_8 |
                        FE_CAN_FEC_AUTO |
                        FE_CAN_QPSK |
                        FE_CAN_QAM_16 |
                        FE_CAN_QAM_32 |
                        FE_CAN_QAM_64 |
                        FE_CAN_QAM_128 |
                        FE_CAN_QAM_256 |
                        FE_CAN_QAM_AUTO |
                        FE_CAN_TRANSMISSION_MODE_AUTO |
                        FE_CAN_GUARD_INTERVAL_AUTO |
                        FE_CAN_HIERARCHY_AUTO |
                        FE_CAN_MUTE_TS |
                        FE_CAN_2G_MODULATION,
                .frequency_min = 42000000, /* Hz */
                .frequency_max = 1002000000, /* Hz */
                .symbol_rate_min = 870000,
                .symbol_rate_max = 11700000
        },
        .init = foo_init,
        .sleep = foo_sleep,
        .release = foo_release,
        .set_frontend = foo_set_frontend,
        .get_frontend = foo_get_frontend,
        .read_status = foo_get_status_and_stats,
        .tune = foo_tune,
        .i2c_gate_ctrl = foo_i2c_gate_ctrl,
        .get_frontend_algo = foo_get_algo,
};

A typical example of such struct in a driver bar meant to be used on Satellite TV reception is:

static const struct dvb_frontend_ops bar_ops = {
        .delsys = { SYS_DVBS, SYS_DVBS2 },
        .info = {
                .name           = "Bar DVB-S/S2 demodulator",
                .frequency_min  = 500000, /* KHz */
                .frequency_max  = 2500000, /* KHz */
                .frequency_stepsize     = 0,
                .symbol_rate_min = 1000000,
                .symbol_rate_max = 45000000,
                .symbol_rate_tolerance = 500,
                .caps = FE_CAN_INVERSION_AUTO |
                        FE_CAN_FEC_AUTO |
                        FE_CAN_QPSK,
        },
        .init = bar_init,
        .sleep = bar_sleep,
        .release = bar_release,
        .set_frontend = bar_set_frontend,
        .get_frontend = bar_get_frontend,
        .read_status = bar_get_status_and_stats,
        .i2c_gate_ctrl = bar_i2c_gate_ctrl,
        .get_frontend_algo = bar_get_algo,
        .tune = bar_tune,

        /* Satellite-specific */
        .diseqc_send_master_cmd = bar_send_diseqc_msg,
        .diseqc_send_burst = bar_send_burst,
        .set_tone = bar_set_tone,
        .set_voltage = bar_set_voltage,
};

Note

1. For satellite digital TV standards (DVB-S, DVB-S2, ISDB-S), the frequencies are specified in kHz, while, for terrestrial and cable standards, they’re specified in Hz. Due to that, if the same frontend supports both types, you’ll need to have two separate dvb_frontend_ops structures, one for each standard.
2. The .i2c_gate_ctrl field is present only when the hardware has allows controlling an I2C gate (either directly of via some GPIO pin), in order to remove the tuner from the I2C bus after a channel is tuned.
3. All new drivers should implement the DVBv5 statistics via .read_status. Yet, there are a number of callbacks meant to get statistics for signal strength, S/N and UCB. Those are there to provide backward compatibility with legacy applications that don’t support the DVBv5 API. Implementing those callbacks are optional. Those callbacks may be removed in the future, after we have all existing drivers supporting DVBv5 stats.
4. Other callbacks are required for satellite TV standards, in order to control LNBf and DiSEqC: .diseqc_send_master_cmd, .diseqc_send_burst, .set_tone, .set_voltage.

The drivers/media/dvb-core/dvb_frontend.c has a kernel thread with is responsible for tuning the device. It supports multiple algoritms to detect a channel, as defined at enum dvbfe_algo().

The algorithm to be used is obtained via .get_frontend_algo. If the driver doesn’t fill its field at struct dvb_frontend_ops, it will default to DVBFE_ALGO_SW, meaning that the dvb-core will do a zigzag when tuning, e. g. it will try first to use the specified center frequency f, then, it will do f + Δ, f - Δ, f + 2 x Δ, f - 2 x Δ and so on.

If the hardware has internally a some sort of zigzag algorithm, you should define a .get_frontend_algo function that would return DVBFE_ALGO_HW.

Note

The core frontend support also supports a third type (DVBFE_ALGO_CUSTOM), in order to allow the driver to define its own hardware-assisted algorithm. Very few hardware need to use it nowadays. Using DVBFE_ALGO_CUSTOM require to provide other function callbacks at struct dvb_frontend_ops.

5.1.2. Attaching frontend driver to the bridge driver

Before using the Digital TV frontend core, the bridge driver should attach the frontend demod, tuner and SEC devices and call dvb_register_frontend(), in order to register the new frontend at the subsystem. At device detach/removal, the bridge driver should call dvb_unregister_frontend() to remove the frontend from the core and then dvb_frontend_detach() to free the memory allocated by the frontend drivers.

The drivers should also call dvb_frontend_suspend() as part of their handler for the device_driver.suspend(), and dvb_frontend_resume() as part of their handler for device_driver.resume().

A few other optional functions are provided to handle some special cases.

5.2. Digital TV Frontend statistics

5.2.1. Introduction

Digital TV frontends provide a range of statistics meant to help tuning the device and measuring the quality of service.

For each statistics measurement, the driver should set the type of scale used, or FE_SCALE_NOT_AVAILABLE if the statistics is not available on a given time. Drivers should also provide the number of statistics for each type. that’s usually 1 for most video standards [2].

Drivers should initialize each statistic counters with length and scale at its init code. For example, if the frontend provides signal strength, it should have, on its init code:

struct dtv_frontend_properties *c = &state->fe.dtv_property_cache;

c->strength.len = 1;
c->strength.stat[0].scale = FE_SCALE_NOT_AVAILABLE;

And, when the statistics got updated, set the scale:

c->strength.stat[0].scale = FE_SCALE_DECIBEL;
c->strength.stat[0].uvalue = strength;

[2]

For ISDB-T, it may provide both a global statistics and a per-layer set of statistics. On such cases, len should be equal to 4. The first value corresponds to the global stat; the other ones to each layer, e. g.: c->cnr.stat[0] for global S/N carrier ratio, c->cnr.stat[1] for Layer A S/N carrier ratio, c->cnr.stat[2] for layer B S/N carrier ratio, c->cnr.stat[3] for layer C S/N carrier ratio.

Note

Please prefer to use FE_SCALE_DECIBEL instead of FE_SCALE_RELATIVE for signal strength and CNR measurements.

5.2.2. Groups of statistics

There are several groups of statistics currently supported:

Signal strength (DTV_STAT_SIGNAL_STRENGTH)

• Measures the signal strength level at the analog part of the tuner or demod.
• Typically obtained from the gain applied to the tuner and/or frontend in order to detect the carrier. When no carrier is detected, the gain is at the maximum value (so, strength is on its minimal).
• As the gain is visible through the set of registers that adjust the gain, typically, this statistics is always available [3].
• Drivers should try to make it available all the times, as this statistics can be used when adjusting an antenna position and to check for troubles at the cabling.

[3]	On a few devices, the gain keeps floating if no carrier. On such devices, strength report should check first if carrier is detected at the tuner (FE_HAS_CARRIER, see fe_status), and otherwise return the lowest possible value.

Carrier Signal to Noise ratio (DTV_STAT_CNR)

• Signal to Noise ratio for the main carrier.

• Signal to Noise measurement depends on the device. On some hardware, is available when the main carrier is detected. On those hardware, CNR measurement usually comes from the tuner (e. g. after FE_HAS_CARRIER, see fe_status).

  On other devices, it requires inner FEC decoding, as the frontend measures it indirectly from other parameters (e. g. after FE_HAS_VITERBI, see fe_status).

  Having it available after inner FEC is more common.

Bit counts post-FEC (DTV_STAT_POST_ERROR_BIT_COUNT and DTV_STAT_POST_TOTAL_BIT_COUNT)

• Those counters measure the number of bits and bit errors errors after the forward error correction (FEC) on the inner coding block (after Viterbi, LDPC or other inner code).
• Due to its nature, those statistics depend on full coding lock (e. g. after FE_HAS_SYNC or after FE_HAS_LOCK, see fe_status).

Bit counts pre-FEC (DTV_STAT_PRE_ERROR_BIT_COUNT and DTV_STAT_PRE_TOTAL_BIT_COUNT)

• Those counters measure the number of bits and bit errors errors before the forward error correction (FEC) on the inner coding block (before Viterbi, LDPC or other inner code).
• Not all frontends provide this kind of statistics.
• Due to its nature, those statistics depend on inner coding lock (e. g. after FE_HAS_VITERBI, see fe_status).

Block counts (DTV_STAT_ERROR_BLOCK_COUNT and DTV-STAT_TOTAL_BLOCK_COUNT)

• Those counters measure the number of blocks and block errors errors after the forward error correction (FEC) on the inner coding block (before Viterbi, LDPC or other inner code).
• Due to its nature, those statistics depend on full coding lock (e. g. after FE_HAS_SYNC or after FE_HAS_LOCK, see fe_status).

Note

All counters should be monotonically increased as they’re collected from the hardware.

A typical example of the logic that handle status and statistics is:

static int foo_get_status_and_stats(struct dvb_frontend *fe)
{
        struct foo_state *state = fe->demodulator_priv;
        struct dtv_frontend_properties *c = &fe->dtv_property_cache;

        int rc;
        enum fe_status *status;

        /* Both status and strength are always available */
        rc = foo_read_status(fe, &status);
        if (rc < 0)
                return rc;

        rc = foo_read_strength(fe);
        if (rc < 0)
                return rc;

        /* Check if CNR is available */
        if (!(fe->status & FE_HAS_CARRIER))
                return 0;

        rc = foo_read_cnr(fe);
        if (rc < 0)
                return rc;

        /* Check if pre-BER stats are available */
        if (!(fe->status & FE_HAS_VITERBI))
                return 0;

        rc = foo_get_pre_ber(fe);
        if (rc < 0)
                return rc;

        /* Check if post-BER stats are available */
        if (!(fe->status & FE_HAS_SYNC))
                return 0;

        rc = foo_get_post_ber(fe);
        if (rc < 0)
                return rc;
}

static const struct dvb_frontend_ops ops = {
        /* ... */
        .read_status = foo_get_status_and_stats,
};

5.2.3. Statistics collect

On almost all frontend hardware, the bit and byte counts are stored by the hardware after a certain amount of time or after the total bit/block counter reaches a certain value (usually programable), for example, on every 1000 ms or after receiving 1,000,000 bits.

So, if you read the registers too soon, you’ll end by reading the same value as in the previous reading, causing the monotonic value to be incremented too often.

Drivers should take the responsibility to avoid too often reads. That can be done using two approaches:

5.2.3.1. if the driver have a bit that indicates when a collected data is ready

Driver should check such bit before making the statistics available.

An example of such behavior can be found at this code snippet (adapted from mb86a20s driver’s logic):

static int foo_get_pre_ber(struct dvb_frontend *fe)
{
        struct foo_state *state = fe->demodulator_priv;
        struct dtv_frontend_properties *c = &fe->dtv_property_cache;
        int rc, bit_error;

        /* Check if the BER measures are already available */
        rc = foo_read_u8(state, 0x54);
        if (rc < 0)
                return rc;

        if (!rc)
                return 0;

        /* Read Bit Error Count */
        bit_error = foo_read_u32(state, 0x55);
        if (bit_error < 0)
                return bit_error;

        /* Read Total Bit Count */
        rc = foo_read_u32(state, 0x51);
        if (rc < 0)
                return rc;

        c->pre_bit_error.stat[0].scale = FE_SCALE_COUNTER;
        c->pre_bit_error.stat[0].uvalue += bit_error;
        c->pre_bit_count.stat[0].scale = FE_SCALE_COUNTER;
        c->pre_bit_count.stat[0].uvalue += rc;

        return 0;
}

5.2.3.2. If the driver doesn’t provide a statistics available check bit

A few devices, however, may not provide a way to check if the stats are available (or the way to check it is unknown). They may not even provide a way to directly read the total number of bits or blocks.

On those devices, the driver need to ensure that it won’t be reading from the register too often and/or estimate the total number of bits/blocks.

On such drivers, a typical routine to get statistics would be like (adapted from dib8000 driver’s logic):

struct foo_state {
        /* ... */

        unsigned long per_jiffies_stats;
}

static int foo_get_pre_ber(struct dvb_frontend *fe)
{
        struct foo_state *state = fe->demodulator_priv;
        struct dtv_frontend_properties *c = &fe->dtv_property_cache;
        int rc, bit_error;
        u64 bits;

        /* Check if time for stats was elapsed */
        if (!time_after(jiffies, state->per_jiffies_stats))
                return 0;

        /* Next stat should be collected in 1000 ms */
        state->per_jiffies_stats = jiffies + msecs_to_jiffies(1000);

        /* Read Bit Error Count */
        bit_error = foo_read_u32(state, 0x55);
        if (bit_error < 0)
                return bit_error;

        /*
         * On this particular frontend, there's no register that
         * would provide the number of bits per 1000ms sample. So,
         * some function would calculate it based on DTV properties
         */
        bits = get_number_of_bits_per_1000ms(fe);

        c->pre_bit_error.stat[0].scale = FE_SCALE_COUNTER;
        c->pre_bit_error.stat[0].uvalue += bit_error;
        c->pre_bit_count.stat[0].scale = FE_SCALE_COUNTER;
        c->pre_bit_count.stat[0].uvalue += bits;

        return 0;
}

Please notice that, on both cases, we’re getting the statistics using the dvb_frontend_ops .read_status callback. The rationale is that the frontend core will automatically call this function periodically (usually, 3 times per second, when the frontend is locked).

That warrants that we won’t miss to collect a counter and increment the monotonic stats at the right time.

5.3. Digital TV Frontend functions and types

struct dvb_frontend_tune_settings

parameters to adjust frontend tuning

Definition

struct dvb_frontend_tune_settings {
  int min_delay_ms;
  int step_size;
  int max_drift;
};

Members

min_delay_ms

minimum delay for tuning, in ms

step_size

step size between two consecutive frequencies

max_drift

maximum drift

NOTE

step_size is in Hz, for terrestrial/cable or kHz for satellite

struct dvb_tuner_info

Frontend name and min/max ranges/bandwidths

Definition

struct dvb_tuner_info {
  char name;
  u32 frequency_min;
  u32 frequency_max;
  u32 frequency_step;
  u32 bandwidth_min;
  u32 bandwidth_max;
  u32 bandwidth_step;
};

Members

name

name of the Frontend

frequency_min

minimal frequency supported

frequency_max

maximum frequency supported

frequency_step

frequency step

bandwidth_min

minimal frontend bandwidth supported

bandwidth_max

maximum frontend bandwidth supported

bandwidth_step

frontend bandwidth step

NOTE

frequency parameters are in Hz, for terrestrial/cable or kHz for satellite.

struct analog_parameters

Parameters to tune into an analog/radio channel

Definition

struct analog_parameters {
  unsigned int frequency;
  unsigned int mode;
  unsigned int audmode;
  u64 std;
};

Members

frequency

Frequency used by analog TV tuner (either in 62.5 kHz step, for TV, or 62.5 Hz for radio)

mode

Tuner mode, as defined on enum v4l2_tuner_type

audmode

Audio mode as defined for the rxsubchans field at videodev2.h, e. g. V4L2_TUNER_MODE_*

std

TV standard bitmap as defined at videodev2.h, e. g. V4L2_STD_*

Description

Hybrid tuners should be supported by both V4L2 and DVB APIs. This struct contains the data that are used by the V4L2 side. To avoid dependencies from V4L2 headers, all enums here are declared as integers.

enum dvbfe_algo

defines the algorithm used to tune into a channel

Constants

DVBFE_ALGO_HW

Hardware Algorithm - Devices that support this algorithm do everything in hardware and no software support is needed to handle them. Requesting these devices to LOCK is the only thing required, device is supposed to do everything in the hardware.

DVBFE_ALGO_SW

Software Algorithm - These are dumb devices, that require software to do everything

DVBFE_ALGO_CUSTOM

Customizable Agorithm - Devices having this algorithm can be customized to have specific algorithms in the frontend driver, rather than simply doing a software zig-zag. In this case the zigzag maybe hardware assisted or it maybe completely done in hardware. In all cases, usage of this algorithm, in conjunction with the search and track callbacks, utilizes the driver specific algorithm.

DVBFE_ALGO_RECOVERY

Recovery Algorithm - These devices have AUTO recovery capabilities from LOCK failure

enum dvbfe_search

search callback possible return status

Constants

DVBFE_ALGO_SEARCH_SUCCESS

The frontend search algorithm completed and returned successfully

DVBFE_ALGO_SEARCH_ASLEEP

The frontend search algorithm is sleeping

DVBFE_ALGO_SEARCH_FAILED

The frontend search for a signal failed

DVBFE_ALGO_SEARCH_INVALID

The frontend search algorith was probably supplied with invalid parameters and the search is an invalid one

DVBFE_ALGO_SEARCH_AGAIN

The frontend search algorithm was requested to search again

DVBFE_ALGO_SEARCH_ERROR

The frontend search algorithm failed due to some error

struct dvb_tuner_ops

Tuner information and callbacks

Definition

struct dvb_tuner_ops {
  struct dvb_tuner_info info;
  void (* release) (struct dvb_frontend *fe);
  int (* init) (struct dvb_frontend *fe);
  int (* sleep) (struct dvb_frontend *fe);
  int (* suspend) (struct dvb_frontend *fe);
  int (* resume) (struct dvb_frontend *fe);
  int (* set_params) (struct dvb_frontend *fe);
  int (* set_analog_params) (struct dvb_frontend *fe, struct analog_parameters *p);
  int (* set_config) (struct dvb_frontend *fe, void *priv_cfg);
  int (* get_frequency) (struct dvb_frontend *fe, u32 *frequency);
  int (* get_bandwidth) (struct dvb_frontend *fe, u32 *bandwidth);
  int (* get_if_frequency) (struct dvb_frontend *fe, u32 *frequency);
#define TUNER_STATUS_LOCKED 1
#define TUNER_STATUS_STEREO 2
  int (* get_status) (struct dvb_frontend *fe, u32 *status);
  int (* get_rf_strength) (struct dvb_frontend *fe, u16 *strength);
  int (* get_afc) (struct dvb_frontend *fe, s32 *afc);
  int (* calc_regs) (struct dvb_frontend *fe, u8 *buf, int buf_len);
  int (* set_frequency) (struct dvb_frontend *fe, u32 frequency);
  int (* set_bandwidth) (struct dvb_frontend *fe, u32 bandwidth);
};

Members

info

embedded struct dvb_tuner_info with tuner properties

release

callback function called when frontend is dettached. drivers should free any allocated memory.

init

callback function used to initialize the tuner device.

sleep

callback function used to put the tuner to sleep.

suspend

callback function used to inform that the Kernel will suspend.

resume

callback function used to inform that the Kernel is resuming from suspend.

set_params

callback function used to inform the tuner to tune into a digital TV channel. The properties to be used are stored at dvb_frontend.dtv_property_cache;. The tuner demod can change the parameters to reflect the changes needed for the channel to be tuned, and update statistics. This is the recommended way to set the tuner parameters and should be used on newer drivers.

set_analog_params

callback function used to tune into an analog TV channel on hybrid tuners. It passes analog_parameters; to the driver.

set_config

callback function used to send some tuner-specific parameters.

get_frequency

get the actual tuned frequency

get_bandwidth

get the bandwitdh used by the low pass filters

get_if_frequency

get the Intermediate Frequency, in Hz. For baseband, should return 0.

get_status

returns the frontend lock status

get_rf_strength

returns the RF signal strengh. Used mostly to support analog TV and radio. Digital TV should report, instead, via DVBv5 API (dvb_frontend.dtv_property_cache;).

get_afc

Used only by analog TV core. Reports the frequency drift due to AFC.

calc_regs

callback function used to pass register data settings for simple tuners. Shouldn’t be used on newer drivers.

set_frequency

Set a new frequency. Shouldn’t be used on newer drivers.

set_bandwidth

Set a new frequency. Shouldn’t be used on newer drivers.

NOTE

frequencies used on get_frequency and set_frequency are in Hz for terrestrial/cable or kHz for satellite.

struct analog_demod_info

Information struct for analog TV part of the demod

Definition

struct analog_demod_info {
  char * name;
};

Members

name

Name of the analog TV demodulator

struct analog_demod_ops

Demodulation information and callbacks for analog TV and radio

Definition

struct analog_demod_ops {
  struct analog_demod_info info;
  void (* set_params) (struct dvb_frontend *fe, struct analog_parameters *params);
  int (* has_signal) (struct dvb_frontend *fe, u16 *signal);
  int (* get_afc) (struct dvb_frontend *fe, s32 *afc);
  void (* tuner_status) (struct dvb_frontend *fe);
  void (* standby) (struct dvb_frontend *fe);
  void (* release) (struct dvb_frontend *fe);
  int (* i2c_gate_ctrl) (struct dvb_frontend *fe, int enable);
  int (* set_config) (struct dvb_frontend *fe, void *priv_cfg);
};

Members

info

pointer to struct analog_demod_info

set_params

callback function used to inform the demod to set the demodulator parameters needed to decode an analog or radio channel. The properties are passed via struct analog_params;.

has_signal

returns 0xffff if has signal, or 0 if it doesn’t.

get_afc

Used only by analog TV core. Reports the frequency drift due to AFC.

tuner_status

callback function that returns tuner status bits, e. g. TUNER_STATUS_LOCKED and TUNER_STATUS_STEREO.

standby

set the tuner to standby mode.

release

callback function called when frontend is dettached. drivers should free any allocated memory.

i2c_gate_ctrl

controls the I2C gate. Newer drivers should use I2C mux support instead.

set_config

callback function used to send some tuner-specific parameters.

struct dvb_frontend_ops

Demodulation information and callbacks for ditialt TV

Definition

struct dvb_frontend_ops {
  struct dvb_frontend_info info;
  u8 delsys;
  void (* detach) (struct dvb_frontend *fe);
  void (* release) (struct dvb_frontend* fe);
  void (* release_sec) (struct dvb_frontend* fe);
  int (* init) (struct dvb_frontend* fe);
  int (* sleep) (struct dvb_frontend* fe);
  int (* write) (struct dvb_frontend* fe, const u8 buf[], int len);
  int (* tune) (struct dvb_frontend* fe,bool re_tune,unsigned int mode_flags,unsigned int *delay, enum fe_status *status);
  enum dvbfe_algo (* get_frontend_algo) (struct dvb_frontend *fe);
  int (* set_frontend) (struct dvb_frontend *fe);
  int (* get_tune_settings) (struct dvb_frontend* fe, struct dvb_frontend_tune_settings* settings);
  int (* get_frontend) (struct dvb_frontend *fe, struct dtv_frontend_properties *props);
  int (* read_status) (struct dvb_frontend *fe, enum fe_status *status);
  int (* read_ber) (struct dvb_frontend* fe, u32* ber);
  int (* read_signal_strength) (struct dvb_frontend* fe, u16* strength);
  int (* read_snr) (struct dvb_frontend* fe, u16* snr);
  int (* read_ucblocks) (struct dvb_frontend* fe, u32* ucblocks);
  int (* diseqc_reset_overload) (struct dvb_frontend* fe);
  int (* diseqc_send_master_cmd) (struct dvb_frontend* fe, struct dvb_diseqc_master_cmd* cmd);
  int (* diseqc_recv_slave_reply) (struct dvb_frontend* fe, struct dvb_diseqc_slave_reply* reply);
  int (* diseqc_send_burst) (struct dvb_frontend *fe, enum fe_sec_mini_cmd minicmd);
  int (* set_tone) (struct dvb_frontend *fe, enum fe_sec_tone_mode tone);
  int (* set_voltage) (struct dvb_frontend *fe, enum fe_sec_voltage voltage);
  int (* enable_high_lnb_voltage) (struct dvb_frontend* fe, long arg);
  int (* dishnetwork_send_legacy_command) (struct dvb_frontend* fe, unsigned long cmd);
  int (* i2c_gate_ctrl) (struct dvb_frontend* fe, int enable);
  int (* ts_bus_ctrl) (struct dvb_frontend* fe, int acquire);
  int (* set_lna) (struct dvb_frontend *);
  enum dvbfe_search (* search) (struct dvb_frontend *fe);
  struct dvb_tuner_ops tuner_ops;
  struct analog_demod_ops analog_ops;
  int (* set_property) (struct dvb_frontend* fe, struct dtv_property* tvp);
  int (* get_property) (struct dvb_frontend* fe, struct dtv_property* tvp);
};

Members

info

embedded struct dvb_tuner_info with tuner properties

delsys

Delivery systems supported by the frontend

detach

callback function called when frontend is detached. drivers should clean up, but not yet free the struct dvb_frontend allocation.

release

callback function called when frontend is ready to be freed. drivers should free any allocated memory.

release_sec

callback function requesting that the Satelite Equipment Control (SEC) driver to release and free any memory allocated by the driver.

init

callback function used to initialize the tuner device.

sleep

callback function used to put the tuner to sleep.

write

callback function used by some demod legacy drivers to allow other drivers to write data into their registers. Should not be used on new drivers.

tune

callback function used by demod drivers that use DVBFE_ALGO_HW; to tune into a frequency.

get_frontend_algo

returns the desired hardware algorithm.

set_frontend

callback function used to inform the demod to set the parameters for demodulating a digital TV channel. The properties to be used are stored at dvb_frontend.dtv_property_cache;. The demod can change the parameters to reflect the changes needed for the channel to be decoded, and update statistics.

get_tune_settings

callback function

get_frontend

callback function used to inform the parameters actuall in use. The properties to be used are stored at dvb_frontend.dtv_property_cache; and update statistics. Please notice that it should not return an error code if the statistics are not available because the demog is not locked.

read_status

returns the locking status of the frontend.

read_ber

legacy callback function to return the bit error rate. Newer drivers should provide such info via DVBv5 API, e. g. set_frontend;/get_frontend;, implementing this callback only if DVBv3 API compatibility is wanted.

read_signal_strength

legacy callback function to return the signal strength. Newer drivers should provide such info via DVBv5 API, e. g. set_frontend;/get_frontend;, implementing this callback only if DVBv3 API compatibility is wanted.

read_snr

legacy callback function to return the Signal/Noise rate. Newer drivers should provide such info via DVBv5 API, e. g. set_frontend;/get_frontend;, implementing this callback only if DVBv3 API compatibility is wanted.

read_ucblocks

legacy callback function to return the Uncorrected Error Blocks. Newer drivers should provide such info via DVBv5 API, e. g. set_frontend;/get_frontend;, implementing this callback only if DVBv3 API compatibility is wanted.

diseqc_reset_overload

callback function to implement the FE_DISEQC_RESET_OVERLOAD ioctl (only Satellite)

diseqc_send_master_cmd

callback function to implement the FE_DISEQC_SEND_MASTER_CMD ioctl (only Satellite).

diseqc_recv_slave_reply

callback function to implement the FE_DISEQC_RECV_SLAVE_REPLY ioctl (only Satellite)

diseqc_send_burst

callback function to implement the FE_DISEQC_SEND_BURST ioctl (only Satellite).

set_tone

callback function to implement the FE_SET_TONE ioctl (only Satellite).

set_voltage

callback function to implement the FE_SET_VOLTAGE ioctl (only Satellite).

enable_high_lnb_voltage

callback function to implement the FE_ENABLE_HIGH_LNB_VOLTAGE ioctl (only Satellite).

dishnetwork_send_legacy_command

callback function to implement the FE_DISHNETWORK_SEND_LEGACY_CMD ioctl (only Satellite). Drivers should not use this, except when the DVB core emulation fails to provide proper support (e.g. if set_voltage takes more than 8ms to work), and when backward compatibility with this legacy API is required.

i2c_gate_ctrl

controls the I2C gate. Newer drivers should use I2C mux support instead.

ts_bus_ctrl

callback function used to take control of the TS bus.

set_lna

callback function to power on/off/auto the LNA.

search

callback function used on some custom algo search algos.

tuner_ops

pointer to struct dvb_tuner_ops

analog_ops

pointer to struct analog_demod_ops

set_property

callback function to allow the frontend to validade incoming properties. Should not be used on new drivers.

get_property

callback function to allow the frontend to override outcoming properties. Should not be used on new drivers.

struct dtv_frontend_properties

contains a list of properties that are specific to a digital TV standard.

Definition

struct dtv_frontend_properties {
  u32 frequency;
  enum fe_modulation modulation;
  enum fe_sec_voltage voltage;
  enum fe_sec_tone_mode sectone;
  enum fe_spectral_inversion inversion;
  enum fe_code_rate fec_inner;
  enum fe_transmit_mode transmission_mode;
  u32 bandwidth_hz;
  enum fe_guard_interval guard_interval;
  enum fe_hierarchy hierarchy;
  u32 symbol_rate;
  enum fe_code_rate code_rate_HP;
  enum fe_code_rate code_rate_LP;
  enum fe_pilot pilot;
  enum fe_rolloff rolloff;
  enum fe_delivery_system delivery_system;
  enum fe_interleaving interleaving;
  u8 isdbt_partial_reception;
  u8 isdbt_sb_mode;
  u8 isdbt_sb_subchannel;
  u32 isdbt_sb_segment_idx;
  u32 isdbt_sb_segment_count;
  u8 isdbt_layer_enabled;
  struct layer;
  u32 stream_id;
  u8 atscmh_fic_ver;
  u8 atscmh_parade_id;
  u8 atscmh_nog;
  u8 atscmh_tnog;
  u8 atscmh_sgn;
  u8 atscmh_prc;
  u8 atscmh_rs_frame_mode;
  u8 atscmh_rs_frame_ensemble;
  u8 atscmh_rs_code_mode_pri;
  u8 atscmh_rs_code_mode_sec;
  u8 atscmh_sccc_block_mode;
  u8 atscmh_sccc_code_mode_a;
  u8 atscmh_sccc_code_mode_b;
  u8 atscmh_sccc_code_mode_c;
  u8 atscmh_sccc_code_mode_d;
  u32 lna;
  struct dtv_fe_stats strength;
  struct dtv_fe_stats cnr;
  struct dtv_fe_stats pre_bit_error;
  struct dtv_fe_stats pre_bit_count;
  struct dtv_fe_stats post_bit_error;
  struct dtv_fe_stats post_bit_count;
  struct dtv_fe_stats block_error;
  struct dtv_fe_stats block_count;
};

Members

frequency

frequency in Hz for terrestrial/cable or in kHz for Satellite

modulation

Frontend modulation type

voltage

SEC voltage (only Satellite)

sectone

SEC tone mode (only Satellite)

inversion

Spectral inversion

fec_inner

Forward error correction inner Code Rate

transmission_mode

Transmission Mode

bandwidth_hz

Bandwidth, in Hz. A zero value means that userspace wants to autodetect.

guard_interval

Guard Interval

hierarchy

Hierarchy

symbol_rate

Symbol Rate

code_rate_HP

high priority stream code rate

code_rate_LP

low priority stream code rate

pilot

Enable/disable/autodetect pilot tones

rolloff

Rolloff factor (alpha)

delivery_system

FE delivery system (e. g. digital TV standard)

interleaving

interleaving

isdbt_partial_reception

ISDB-T partial reception (only ISDB standard)

isdbt_sb_mode

ISDB-T Sound Broadcast (SB) mode (only ISDB standard)

isdbt_sb_subchannel

ISDB-T SB subchannel (only ISDB standard)

isdbt_sb_segment_idx

ISDB-T SB segment index (only ISDB standard)

isdbt_sb_segment_count

ISDB-T SB segment count (only ISDB standard)

isdbt_layer_enabled

ISDB Layer enabled (only ISDB standard)

layer

per layer interleaving.

stream_id

If different than zero, enable substream filtering, if hardware supports (DVB-S2 and DVB-T2).

atscmh_fic_ver

Version number of the FIC (Fast Information Channel) signaling data (only ATSC-M/H)

atscmh_parade_id

Parade identification number (only ATSC-M/H)

atscmh_nog

Number of MH groups per MH subframe for a designated parade (only ATSC-M/H)

atscmh_tnog

Total number of MH groups including all MH groups belonging to all MH parades in one MH subframe (only ATSC-M/H)

atscmh_sgn

Start group number (only ATSC-M/H)

atscmh_prc

Parade repetition cycle (only ATSC-M/H)

atscmh_rs_frame_mode

Reed Solomon (RS) frame mode (only ATSC-M/H)

atscmh_rs_frame_ensemble

RS frame ensemble (only ATSC-M/H)

atscmh_rs_code_mode_pri

RS code mode pri (only ATSC-M/H)

atscmh_rs_code_mode_sec

RS code mode sec (only ATSC-M/H)

atscmh_sccc_block_mode

Series Concatenated Convolutional Code (SCCC) Block Mode (only ATSC-M/H)

atscmh_sccc_code_mode_a

SCCC code mode A (only ATSC-M/H)

atscmh_sccc_code_mode_b

SCCC code mode B (only ATSC-M/H)

atscmh_sccc_code_mode_c

SCCC code mode C (only ATSC-M/H)

atscmh_sccc_code_mode_d

SCCC code mode D (only ATSC-M/H)

lna

Power ON/OFF/AUTO the Linear Now-noise Amplifier (LNA)

strength

DVBv5 API statistics: Signal Strength

cnr

DVBv5 API statistics: Signal to Noise ratio of the (main) carrier

pre_bit_error

DVBv5 API statistics: pre-Viterbi bit error count

pre_bit_count

DVBv5 API statistics: pre-Viterbi bit count

post_bit_error

DVBv5 API statistics: post-Viterbi bit error count

post_bit_count

DVBv5 API statistics: post-Viterbi bit count

block_error

DVBv5 API statistics: block error count

block_count

DVBv5 API statistics: block count

NOTE

derivated statistics like Uncorrected Error blocks (UCE) are calculated on userspace.

Only a subset of the properties are needed for a given delivery system. For more info, consult the media_api.html with the documentation of the Userspace API.

struct dvb_frontend

Frontend structure to be used on drivers.

Definition

struct dvb_frontend {
  struct kref refcount;
  struct dvb_frontend_ops ops;
  struct dvb_adapter * dvb;
  void * demodulator_priv;
  void * tuner_priv;
  void * frontend_priv;
  void * sec_priv;
  void * analog_demod_priv;
  struct dtv_frontend_properties dtv_property_cache;
#define DVB_FRONTEND_COMPONENT_TUNER 0
#define DVB_FRONTEND_COMPONENT_DEMOD 1
  int (* callback) (void *adapter_priv, int component, int cmd, int arg);
  int id;
  unsigned int exit;
};

Members

refcount

refcount to keep track of struct dvb_frontend references

ops

embedded struct dvb_frontend_ops

dvb

pointer to struct dvb_adapter

demodulator_priv

demod private data

tuner_priv

tuner private data

frontend_priv

frontend private data

sec_priv

SEC private data

analog_demod_priv

Analog demod private data

dtv_property_cache

embedded struct dtv_frontend_properties

callback

callback function used on some drivers to call either the tuner or the demodulator.

id

Frontend ID

exit

Used to inform the DVB core that the frontend thread should exit (usually, means that the hardware got disconnected.

int dvb_register_frontend(struct dvb_adapter * dvb, struct dvb_frontend * fe)

Registers a DVB frontend at the adapter

Parameters

struct dvb_adapter * dvb

pointer to the dvb adapter

struct dvb_frontend * fe

pointer to the frontend struct

Description

Allocate and initialize the private data needed by the frontend core to manage the frontend and calls dvb_register_device() to register a new frontend. It also cleans the property cache that stores the frontend parameters and selects the first available delivery system.

int dvb_unregister_frontend(struct dvb_frontend * fe)

Unregisters a DVB frontend

Parameters

struct dvb_frontend * fe

pointer to the frontend struct

Description

Stops the frontend kthread, calls dvb_unregister_device() and frees the private frontend data allocated by dvb_register_frontend().

NOTE

This function doesn’t frees the memory allocated by the demod, by the SEC driver and by the tuner. In order to free it, an explicit call to dvb_frontend_detach() is needed, after calling this function.

void dvb_frontend_detach(struct dvb_frontend * fe)

Detaches and frees frontend specific data

Parameters

struct dvb_frontend * fe

pointer to the frontend struct

Description

This function should be called after dvb_unregister_frontend(). It calls the SEC, tuner and demod release functions: dvb_frontend_ops.release_sec, dvb_frontend_ops.tuner_ops.release, dvb_frontend_ops.analog_ops.release and dvb_frontend_ops.release.

If the driver is compiled with CONFIG_MEDIA_ATTACH, it also decreases the module reference count, needed to allow userspace to remove the previously used DVB frontend modules.

int dvb_frontend_suspend(struct dvb_frontend * fe)

Suspends a Digital TV frontend

Parameters

struct dvb_frontend * fe

pointer to the frontend struct

Description

This function prepares a Digital TV frontend to suspend.

In order to prepare the tuner to suspend, if dvb_frontend_ops.tuner_ops.suspend() is available, it calls it. Otherwise, it will call dvb_frontend_ops.tuner_ops.sleep(), if available.

It will also call dvb_frontend_ops.sleep() to put the demod to suspend.

The drivers should also call dvb_frontend_suspend() as part of their handler for the device_driver.suspend().

int dvb_frontend_resume(struct dvb_frontend * fe)

Resumes a Digital TV frontend

Parameters

struct dvb_frontend * fe

pointer to the frontend struct

Description

This function resumes the usual operation of the tuner after resume.

In order to resume the frontend, it calls the demod dvb_frontend_ops.init().

If dvb_frontend_ops.tuner_ops.resume() is available, It, it calls it. Otherwise,t will call dvb_frontend_ops.tuner_ops.init(), if available.

Once tuner and demods are resumed, it will enforce that the SEC voltage and tone are restored to their previous values and wake up the frontend’s kthread in order to retune the frontend.

The drivers should also call dvb_frontend_resume() as part of their handler for the device_driver.resume().

void dvb_frontend_reinitialise(struct dvb_frontend * fe)

forces a reinitialisation at the frontend

Parameters

struct dvb_frontend * fe

pointer to the frontend struct

Description

Calls dvb_frontend_ops.init() and dvb_frontend_ops.tuner_ops.init(), and resets SEC tone and voltage (for Satellite systems).

NOTE

Currently, this function is used only by one driver (budget-av). It seems to be due to address some special issue with that specific frontend.

void dvb_frontend_sleep_until(ktime_t * waketime, u32 add_usec)

Sleep for the amount of time given by add_usec parameter

Parameters

ktime_t * waketime

pointer to a struct ktime_t

u32 add_usec

time to sleep, in microseconds

Description

This function is used to measure the time required for the FE_DISHNETWORK_SEND_LEGACY_CMD ioctl to work. It needs to be as precise as possible, as it affects the detection of the dish tone command at the satellite subsystem.

Its used internally by the DVB frontend core, in order to emulate FE_DISHNETWORK_SEND_LEGACY_CMD using the dvb_frontend_ops.set_voltage() callback.

NOTE

it should not be used at the drivers, as the emulation for the legacy callback is provided by the Kernel. The only situation where this should be at the drivers is when there are some bugs at the hardware that would prevent the core emulation to work. On such cases, the driver would be writing a dvb_frontend_ops.dishnetwork_send_legacy_command() and calling this function directly.

6. Digital TV Demux kABI

6.1. Digital TV Demux

The Kernel Digital TV Demux kABI defines a driver-internal interface for registering low-level, hardware specific driver to a hardware independent demux layer. It is only of interest for Digital TV device driver writers. The header file for this kABI is named demux.h and located in drivers/media/dvb-core.

The demux kABI should be implemented for each demux in the system. It is used to select the TS source of a demux and to manage the demux resources. When the demux client allocates a resource via the demux kABI, it receives a pointer to the kABI of that resource.

Each demux receives its TS input from a DVB front-end or from memory, as set via this demux kABI. In a system with more than one front-end, the kABI can be used to select one of the DVB front-ends as a TS source for a demux, unless this is fixed in the HW platform.

The demux kABI only controls front-ends regarding to their connections with demuxes; the kABI used to set the other front-end parameters, such as tuning, are devined via the Digital TV Frontend kABI.

The functions that implement the abstract interface demux should be defined static or module private and registered to the Demux core for external access. It is not necessary to implement every function in the struct &dmx_demux. For example, a demux interface might support Section filtering, but not PES filtering. The kABI client is expected to check the value of any function pointer before calling the function: the value of NULL means that the function is not available.

Whenever the functions of the demux API modify shared data, the possibilities of lost update and race condition problems should be addressed, e.g. by protecting parts of code with mutexes.

Note that functions called from a bottom half context must not sleep. Even a simple memory allocation without using GFP_ATOMIC can result in a kernel thread being put to sleep if swapping is needed. For example, the Linux Kernel calls the functions of a network device interface from a bottom half context. Thus, if a demux kABI function is called from network device code, the function must not sleep.

7. Demux Callback API

7.1. Demux Callback

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.

enum ts_filter_type

filter type bitmap for dmx_ts_feed.set()

Constants

TS_PACKET

Send TS packets (188 bytes) to callback (default).

TS_PAYLOAD_ONLY

In case TS_PACKET is set, only send the TS payload (<=184 bytes per packet) to callback

TS_DECODER

Send stream to built-in decoder (if present).

TS_DEMUX

In case TS_PACKET is set, send the TS to the demux device, not to the dvr device

struct dmx_ts_feed

Structure that contains a TS feed filter

Definition

struct dmx_ts_feed {
  int is_filtering;
  struct dmx_demux * parent;
  void * priv;
  int (* set) (struct dmx_ts_feed *feed,u16 pid,int type,enum dmx_ts_pes pes_type, ktime_t timeout);
  int (* start_filtering) (struct dmx_ts_feed *feed);
  int (* stop_filtering) (struct dmx_ts_feed *feed);
};

Members

is_filtering

Set to non-zero when filtering in progress

parent

pointer to struct dmx_demux

priv

pointer to private data of the API client

set

sets the TS filter

start_filtering

starts TS filtering

stop_filtering

stops TS filtering

Description

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.

struct dmx_section_filter

Structure that describes a section filter

Definition

struct dmx_section_filter {
  u8 filter_value;
  u8 filter_mask;
  u8 filter_mode;
  struct dmx_section_feed * parent;
  void * priv;
};

Members

filter_value

Contains up to 16 bytes (128 bits) of the TS section header that will be matched by the section filter

filter_mask

Contains a 16 bytes (128 bits) filter mask with the bits specified by filter_value that will be used on the filter match logic.

filter_mode

Contains a 16 bytes (128 bits) filter mode.

parent

Pointer to struct dmx_section_feed.

priv

Pointer to private data of the API client.

Description

The 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.

struct dmx_section_feed

Structure that contains a section feed filter

Definition

struct dmx_section_feed {
  int is_filtering;
  struct dmx_demux * parent;
  void * priv;
  int check_crc;
  int (* set) (struct dmx_section_feed *feed,u16 pid, int check_crc);
  int (* allocate_filter) (struct dmx_section_feed *feed, struct dmx_section_filter **filter);
  int (* release_filter) (struct dmx_section_feed *feed, struct dmx_section_filter *filter);
  int (* start_filtering) (struct dmx_section_feed *feed);
  int (* stop_filtering) (struct dmx_section_feed *feed);
};

Members

is_filtering

Set to non-zero when filtering in progress

parent

pointer to struct dmx_demux

priv

pointer to private data of the API client

check_crc

If non-zero, check the CRC values of filtered sections.

set

sets the section filter

allocate_filter

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.

release_filter

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.

start_filtering

starts section filtering

stop_filtering

stops section filtering

Description

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.

dmx_ts_cb

Typedef: DVB demux TS filter callback function prototype

Syntax

int dmx_ts_cb (const u8 * buffer1, size_t buffer1_length, const u8 * buffer2, size_t buffer2_length, struct dmx_ts_feed * source);

Parameters

const u8 * buffer1

Pointer to the start of the filtered TS packets.

size_t buffer1_length

Length of the TS data in buffer1.

const u8 * buffer2

Pointer to the tail of the filtered TS packets, or NULL.

size_t buffer2_length

Length of the TS data in buffer2.

struct dmx_ts_feed * source

Indicates which TS feed is the source of the callback.

Description

This function callback prototype, provided by the client of the demux API, is called from the demux code. The function is only called when filtering on a TS feed has been enabled using the start_filtering() function at the dmx_demux. 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. 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.

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 “wrapped” 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. 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.

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 and return -EOVERFLOW.

The type of data returned to the callback can be selected by the dmx_ts_feed.**set** function. The type parameter decides if the raw TS packet (TS_PACKET) or just the payload (TS_PACKET|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.

Return

• 0, on success;
• -EOVERFLOW, on buffer overflow.

dmx_section_cb

Typedef: DVB demux TS filter callback function prototype

Syntax

int dmx_section_cb (const u8 * buffer1, size_t buffer1_len, const u8 * buffer2, size_t buffer2_len, struct dmx_section_filter * source);

Parameters

const u8 * buffer1

Pointer to the start of the filtered section, e.g. within the circular buffer of the demux driver.

size_t buffer1_len

Length of the filtered section data in buffer1, including headers and CRC.

const u8 * buffer2

Pointer to the tail of the filtered section data, or NULL. Useful to handle the wrapping of a circular buffer.

size_t buffer2_len

Length of the filtered section data in buffer2, including headers and CRC.

struct dmx_section_filter * source

Indicates which section feed is the source of the callback.

Description

This function callback prototype, 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 dmx_ts_feed.**start_filtering**. 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 dmx_ts_feed.**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.

enum dmx_frontend_source

Used to identify the type of frontend

Constants

DMX_MEMORY_FE

The source of the demux is memory. It means that the MPEG-TS to be filtered comes from userspace, via write() syscall.

DMX_FRONTEND_0

The source of the demux is a frontend connected to the demux.

struct dmx_frontend

Structure that lists the frontends associated with a demux

Definition

struct dmx_frontend {
  struct list_head connectivity_list;
  enum dmx_frontend_source source;
};

Members

connectivity_list

List of front-ends that can be connected to a particular demux;

source

Type of the frontend.

Description

FIXME: this structure should likely be replaced soon by some

media-controller based logic.

enum dmx_demux_caps

MPEG-2 TS Demux capabilities bitmap

Constants

DMX_TS_FILTERING

set if TS filtering is supported;

DMX_SECTION_FILTERING

set if section filtering is supported;

DMX_MEMORY_BASED_FILTERING

set if write() available.

Description

Those flags are OR’ed in the dmx_demux.capabilities field

DMX_FE_ENTRY(list)

Casts elements in the list of registered front-ends from the generic type struct list_head to the type * struct dmx_frontend

Parameters

list

list of struct dmx_frontend

struct dmx_demux

Structure that contains the demux capabilities and callbacks.

Definition

struct dmx_demux {
  enum dmx_demux_caps capabilities;
  struct dmx_frontend * frontend;
  void * priv;
  int (* open) (struct dmx_demux *demux);
  int (* close) (struct dmx_demux *demux);
  int (* write) (struct dmx_demux *demux, const char __user *buf, size_t count);
  int (* allocate_ts_feed) (struct dmx_demux *demux,struct dmx_ts_feed **feed, dmx_ts_cb callback);
  int (* release_ts_feed) (struct dmx_demux *demux, struct dmx_ts_feed *feed);
  int (* allocate_section_feed) (struct dmx_demux *demux,struct dmx_section_feed **feed, dmx_section_cb callback);
  int (* release_section_feed) (struct dmx_demux *demux, struct dmx_section_feed *feed);
  int (* add_frontend) (struct dmx_demux *demux, struct dmx_frontend *frontend);
  int (* remove_frontend) (struct dmx_demux *demux, struct dmx_frontend *frontend);
  struct list_head *(* get_frontends) (struct dmx_demux *demux);
  int (* connect_frontend) (struct dmx_demux *demux, struct dmx_frontend *frontend);
  int (* disconnect_frontend) (struct dmx_demux *demux);
  int (* get_pes_pids) (struct dmx_demux *demux, u16 *pids);
};

Members

capabilities

Bitfield of capability flags.

frontend

Front-end connected to the demux

priv

Pointer to private data of the API client

open

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. The demux function parameter contains a pointer to the demux API and instance data. It returns: 0 on success; -EUSERS, if maximum usage count was reached; -EINVAL, on bad parameter.

close

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. The demux function parameter contains a pointer to the demux API and instance data. It returns: 0 on success; -ENODEV, if demux was not in use (e. g. no users); -EINVAL, on bad parameter.

write

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. The demux function parameter contains a pointer to the demux API and instance data. The buf function parameter contains a pointer to the TS data in kernel-space memory. The count function parameter contains the length of the TS data. It returns: 0 on success; -ERESTARTSYS, if mutex lock was interrupted; -EINTR, if a signal handling is pending; -ENODEV, if demux was removed; -EINVAL, on bad parameter.

allocate_ts_feed

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. The demux function parameter contains a pointer to the demux API and instance data. The feed function parameter contains a pointer to the TS feed API and instance data. The callback function parameter contains a pointer to the callback function for passing received TS packet. It returns: 0 on success; -ERESTARTSYS, if mutex lock was interrupted; -EBUSY, if no more TS feeds is available; -EINVAL, on bad parameter.

release_ts_feed

Releases the resources allocated with allocate_ts_feed. Any filtering in progress on the TS feed should be stopped before calling this function. The demux function parameter contains a pointer to the demux API and instance data. The feed function parameter contains a pointer to the TS feed API and instance data. It returns: 0 on success; -EINVAL on bad parameter.

allocate_section_feed

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. The demux function parameter contains a pointer to the demux API and instance data. The feed function parameter contains a pointer to the TS feed API and instance data. The callback function parameter contains a pointer to the callback function for passing received TS packet. It returns: 0 on success; -EBUSY, if no more TS feeds is available; -EINVAL, on bad parameter.

release_section_feed

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. The demux function parameter contains a pointer to the demux API and instance data. The feed function parameter contains a pointer to the TS feed API and instance data. It returns: 0 on success; -EINVAL, on bad parameter.

add_frontend

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. The demux function parameter contains a pointer to the demux API and instance data. The frontend function parameter contains a pointer to the front-end instance data. It returns: 0 on success; -EINVAL, on bad parameter.

remove_frontend

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. The demux function parameter contains a pointer to the demux API and instance data. The frontend function parameter contains a pointer to the front-end instance data. It returns: 0 on success; -ENODEV, if the front-end was not found, -EINVAL, on bad parameter.

get_frontends

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. 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 struct dmx_frontend . The caller must not free the memory of any of the elements obtained via this function call. The **demux* function parameter contains a pointer to the demux API and instance data. It returns a struct list_head pointer to the list of front-end interfaces, or NULL in the case of an empty list.

connect_frontend

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. 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. The demux function parameter contains a pointer to the demux API and instance data. The frontend function parameter contains a pointer to the front-end instance data. It returns: 0 on success; -EINVAL, on bad parameter.

disconnect_frontend

Disconnects the demux and a front-end previously connected by a connect_frontend call. The demux function parameter contains a pointer to the demux API and instance data. It returns: 0 on success; -EINVAL on bad parameter.

get_pes_pids

Get the PIDs for DMX_PES_AUDIO0, DMX_PES_VIDEO0, DMX_PES_TELETEXT0, DMX_PES_SUBTITLE0 and DMX_PES_PCR0. The demux function parameter contains a pointer to the demux API and instance data. The pids function parameter contains an array with five u16 elements where the PIDs will be stored. It returns: 0 on success; -EINVAL on bad parameter.

8. Digital TV Conditional Access kABI

struct dvb_ca_en50221

Structure describing a CA interface

Definition

struct dvb_ca_en50221 {
  struct module * owner;
  int (* read_attribute_mem) (struct dvb_ca_en50221 *ca, int slot, int address);
  int (* write_attribute_mem) (struct dvb_ca_en50221 *ca, int slot, int address, u8 value);
  int (* read_cam_control) (struct dvb_ca_en50221 *ca, int slot, u8 address);
  int (* write_cam_control) (struct dvb_ca_en50221 *ca, int slot, u8 address, u8 value);
  int (* read_data) (struct dvb_ca_en50221 *ca, int slot, u8 *ebuf, int ecount);
  int (* write_data) (struct dvb_ca_en50221 *ca, int slot, u8 *ebuf, int ecount);
  int (* slot_reset) (struct dvb_ca_en50221 *ca, int slot);
  int (* slot_shutdown) (struct dvb_ca_en50221 *ca, int slot);
  int (* slot_ts_enable) (struct dvb_ca_en50221 *ca, int slot);
  int (* poll_slot_status) (struct dvb_ca_en50221 *ca, int slot, int open);
  void * data;
  void * private;
};

Members

owner

the module owning this structure

read_attribute_mem

function for reading attribute memory on the CAM

write_attribute_mem

function for writing attribute memory on the CAM

read_cam_control

function for reading the control interface on the CAM

write_cam_control

function for reading the control interface on the CAM

read_data

function for reading data (block mode)

write_data

function for writing data (block mode)

slot_reset

function to reset the CAM slot

slot_shutdown

function to shutdown a CAM slot

slot_ts_enable

function to enable the Transport Stream on a CAM slot

poll_slot_status

function to poll slot status. Only necessary if DVB_CA_FLAG_EN50221_IRQ_CAMCHANGE is not set.

data

private data, used by caller.

private

Opaque data used by the dvb_ca core. Do not modify!

NOTE

the read_*, write_* and poll_slot_status functions will be called for different slots concurrently and need to use locks where and if appropriate. There will be no concurrent access to one slot.

void dvb_ca_en50221_camchange_irq(struct dvb_ca_en50221 * pubca, int slot, int change_type)

A CAMCHANGE IRQ has occurred.

Parameters

struct dvb_ca_en50221 * pubca

CA instance.

int slot

Slot concerned.

int change_type

One of the DVB_CA_CAMCHANGE_* values

void dvb_ca_en50221_camready_irq(struct dvb_ca_en50221 * pubca, int slot)

A CAMREADY IRQ has occurred.

Parameters

struct dvb_ca_en50221 * pubca

CA instance.

int slot

Slot concerned.

void dvb_ca_en50221_frda_irq(struct dvb_ca_en50221 * ca, int slot)

An FR or a DA IRQ has occurred.

Parameters

struct dvb_ca_en50221 * ca

CA instance.

int slot

Slot concerned.

int dvb_ca_en50221_init(struct dvb_adapter * dvb_adapter, struct dvb_ca_en50221 * ca, int flags, int slot_count)

Initialise a new DVB CA device.

Parameters

struct dvb_adapter * dvb_adapter

DVB adapter to attach the new CA device to.

struct dvb_ca_en50221 * ca

The dvb_ca instance.

int flags

Flags describing the CA device (DVB_CA_EN50221_FLAG_*).

int slot_count

Number of slots supported.

Description

return 0 on success, nonzero on failure

void dvb_ca_en50221_release(struct dvb_ca_en50221 * ca)

Release a DVB CA device.

Parameters

struct dvb_ca_en50221 * ca

The associated dvb_ca instance.