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diff --git a/Documentation/media/kapi/dtv-frontend.rst b/Documentation/media/kapi/dtv-frontend.rst deleted file mode 100644 index fbc5517c8d5a..000000000000 --- a/Documentation/media/kapi/dtv-frontend.rst +++ /dev/null @@ -1,445 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -Digital TV Frontend kABI ------------------------- - -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 -``include/media/``. - -Demodulator driver -^^^^^^^^^^^^^^^^^^ - -The demodulator driver is responsible to talk with the decoding part of the -hardware. Such driver should implement :c:type:`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 ``include/media/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:: - - #) 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 - :c:type:`dvb_frontend_ops` structures, one for each standard. - #) 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. - #) All new drivers should implement the - :ref:`DVBv5 statistics <dvbv5_stats>` 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. - #) 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``. - -.. |delta| unicode:: U+00394 - -The ``include/media/dvb_frontend.c`` has a kernel thread with is -responsible for tuning the device. It supports multiple algorithms to -detect a channel, as defined at enum :c:func:`dvbfe_algo`. - -The algorithm to be used is obtained via ``.get_frontend_algo``. If the driver -doesn't fill its field at struct :c:type:`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`` + |delta|, ``f`` - |delta|, ``f`` + 2 x |delta|, -``f`` - 2 x |delta| 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 :c:type:`dvb_frontend_ops`. - -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 -:c:func:`dvb_register_frontend()`, -in order to register the new frontend at the subsystem. At device -detach/removal, the bridge driver should call -:c:func:`dvb_unregister_frontend()` to -remove the frontend from the core and then :c:func:`dvb_frontend_detach()` -to free the memory allocated by the frontend drivers. - -The drivers should also call :c:func:`dvb_frontend_suspend()` as part of -their handler for the :c:type:`device_driver`.\ ``suspend()``, and -:c:func:`dvb_frontend_resume()` as -part of their handler for :c:type:`device_driver`.\ ``resume()``. - -A few other optional functions are provided to handle some special cases. - -.. _dvbv5_stats: - -Digital TV Frontend statistics -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Introduction -^^^^^^^^^^^^ - -Digital TV frontends provide a range of -:ref:`statistics <frontend-stat-properties>` 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 [#f2]_. - -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; - -.. [#f2] 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. - -Groups of statistics -^^^^^^^^^^^^^^^^^^^^ - -There are several groups of statistics currently supported: - -Signal strength (:ref:`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 [#f3]_. - - - 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. - - .. [#f3] 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 :c:type:`fe_status`), - and otherwise return the lowest possible value. - -Carrier Signal to Noise ratio (:ref:`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 :c:type:`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 :c:type:`fe_status`). - - Having it available after inner FEC is more common. - -Bit counts post-FEC (:ref:`DTV-STAT-POST-ERROR-BIT-COUNT` and :ref:`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 :c:type:`fe_status`). - -Bit counts pre-FEC (:ref:`DTV-STAT-PRE-ERROR-BIT-COUNT` and :ref:`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 :c:type:`fe_status`). - -Block counts (:ref:`DTV-STAT-ERROR-BLOCK-COUNT` and :ref:`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 :c:type:`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, - }; - -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 programmable), 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: - -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; - } - -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 -:c:type:`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. - -Digital TV Frontend functions and types -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -.. kernel-doc:: include/media/dvb_frontend.h |