536 lines
15 KiB
C
536 lines
15 KiB
C
/* GSM A-bis TRAU frame synchronization as per TS 48.060 / 48.061 */
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/* (C) 2020 by Harald Welte <laforge@gnumonks.org>
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* All Rights Reserved
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*
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* SPDX-License-Identifier: GPL-2.0+
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <stdint.h>
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#include <osmocom/core/msgb.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/core/fsm.h>
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#include "ubit_buf.h"
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#include <osmocom/trau/trau_sync.h>
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#define S(x) (1 << (x))
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#define MAX_TRAU_BYTES 40
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#define T_SYNC 1
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struct sync_pattern {
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/* provided by user */
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const char *name; /*!< human-readable name */
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const uint8_t byte_pattern[MAX_TRAU_BYTES]; /*!< bytes to match against */
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const uint8_t byte_mask[MAX_TRAU_BYTES]; /*!< mask applied before matching */
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uint8_t byte_len; /*!< length of mask in bytes */
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/* generated by code */
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ubit_t ubit_pattern[MAX_TRAU_BYTES*8]; /*!< bits to match against */
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ubit_t ubit_mask[MAX_TRAU_BYTES*8]; /*!< mask applied before matching */
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uint8_t bitcount; /*!< number of high bits in mask */
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};
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static struct sync_pattern sync_patterns[] = {
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[OSMO_TRAU_SYNCP_16_FR_EFR] = {
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/* TS 08.60 Section 4.8.1 */
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.name = "FR/EFR",
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.byte_pattern = {
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0x00, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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},
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.byte_mask = {
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0xff, 0xff, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00, 0x80, 0x00, 0x80, 0x00,
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},
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.byte_len = 40,
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},
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[OSMO_TRAU_SYNCP_8_HR] = {
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/* TS 08.61 Section 6.8.2.1.1 */
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.name = "HR8",
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.byte_pattern = {
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0x00, 0x80, 0x40, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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},
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.byte_mask = {
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0xff, 0x80, 0xC0, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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},
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.byte_len = 20,
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},
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[OSMO_TRAU_SYNCP_8_AMR_LOW] = {
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/* TS 08.61 Section 6.8.2.1.2 */
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/* The frame synchronisation for No_Speech frames and the speech frames of the three lower codec modes */
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.name = "AMR8_LOW",
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.byte_pattern = {
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0x00, 0x80, 0x80, 0x40,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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},
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.byte_mask = {
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0xff, 0x80, 0x80, 0xC0,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x80,
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},
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.byte_len = 20,
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},
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[OSMO_TRAU_SYNCP_8_AMR_6K7] = {
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/* The frame synchronisation for the speech frames for codec mode 6,70 kBit/s */
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.name = "AMR8_67",
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.byte_pattern = {
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0x00, 0x80, 0x80, 0x80,
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0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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},
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.byte_mask = {
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0xff, 0x80, 0x80, 0x80,
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0x80, 0x80, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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0x80, 0x00, 0x80, 0x00,
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},
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.byte_len = 20
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},
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[OSMO_TRAU_SYNCP_8_AMR_7K4] = {
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/* The frame synchronisation for the speech frames for codec mode 7,40 kBit/s */
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.name = "AMR8_74",
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.byte_pattern = {
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0x20, 0x00, 0x80, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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},
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.byte_mask = {
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0xe0, 0x80, 0x80, 0x80,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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},
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.byte_len = 20,
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},
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};
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#if 0
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static struct sync_pattern rbs_ccu_sync_ind_16_pattern = {
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.name ="RBS_CCU_SYNC_IND_16",
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.byte_pattern = {
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0x00, 0x00, 0x01, 0x00,
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0x00, 0x00, 0x01, 0x00,
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0x01, 0x00, 0x01, 0x00,
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},
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.byte_mask = {
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0xff, 0xff, 0x01, 0x00,
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0x01, 0x00, 0x01, 0x00,
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0x01, 0x00, 0x01, 0x00,
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},
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};
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static struct sync_pattern rbs_ccu_data_ind_16_pattern = {
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.name ="RBS_CCU_DATA_IND_16",
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.byte_pattern = {
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0x00, 0x00, 0x01, 0x00,
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},
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.byte_mask = {
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0xff, 0xff, 0x01, 0x00,
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},
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};
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#endif
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static void expand_sync_pattern(struct sync_pattern *pat)
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{
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osmo_pbit2ubit(pat->ubit_pattern, pat->byte_pattern, pat->byte_len*8);
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osmo_pbit2ubit(pat->ubit_mask, pat->byte_mask, pat->byte_len*8);
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}
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static unsigned int count_one_bits(const ubit_t *in, unsigned int in_bits)
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{
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unsigned int i, count = 0;
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for (i = 0; i < in_bits; i++) {
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if (in[i])
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count++;
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}
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return count;
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}
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static void sync_pattern_register(struct sync_pattern *p)
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{
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expand_sync_pattern(p);
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p->bitcount = count_one_bits(p->ubit_mask, p->byte_len*8);
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}
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#if 0
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/*! correlate pattern with unpacked bits from buffer.
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* \param[in] pattern sync_pattern against which we shall compare
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* \param[in] bits unpacked bits to compare against pattern
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* \param[in] num_bits number of unpacked bits
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* \returns number of bits not matching pattern; -1 if insufficient bits available. */
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static int correlate_pattern_ubits(const struct sync_pattern *pattern,
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const ubit_t *bits, size_t num_bits)
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{
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int i, num_wrong = 0;
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if (num_bits < pattern->byte_len*8)
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return -1; /* insufficient data */
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for (i = 0; i < pattern->byte_len *8; i++) {
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/* if mask doesn't contain '1', we can skip this octet */
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if (!pattern->ubit_mask)
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continue;
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if (bits[i] != pattern->ubit_pattern[i])
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num_wrong++;
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}
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return num_wrong;
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}
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#endif
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struct trau_rx_sync_state {
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/*! call-back to be called for every TRAU frame (called with
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* bits=NULL in case of frame sync loss */
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frame_out_cb_t out_cb;
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/*! opaque user data; passed to out_cb */
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void *user_data;
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/*! history of received bits */
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ubit_t history[MAX_TRAU_BYTES*8+1]; /* +1 not required, but helps to expose bugs */
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/*! index of next-to-be-written ubit in history */
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unsigned int history_idx;
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/*! the pattern we are trying to sync to */
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const struct sync_pattern *pattern;
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/*! number of consecutive frames without sync */
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unsigned int num_consecutive_errors;
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};
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/* correlate the history (up to the last received bit) against the pattern */
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static int correlate_history_against_pattern(struct trau_rx_sync_state *tss)
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{
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const struct sync_pattern *pattern = tss->pattern;
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int i, start, num_wrong = 0;
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/* compute index of first bit in history array */
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start = (ARRAY_SIZE(tss->history) + tss->history_idx - pattern->byte_len*8)
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% ARRAY_SIZE(tss->history);
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OSMO_ASSERT(ARRAY_SIZE(tss->history) >= pattern->byte_len*8);
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for (i = 0; i < pattern->byte_len*8; i++) {
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unsigned int pos = (start + i) % ARRAY_SIZE(tss->history);
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/* if mask doesn't contain '1', we can skip this octet */
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if (!pattern->ubit_mask[i])
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continue;
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if (tss->history[pos] != pattern->ubit_pattern[i])
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num_wrong++;
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}
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return num_wrong;
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}
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/* add (append) one ubit to the history; wrap as needed */
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static void rx_history_add_bit(struct trau_rx_sync_state *tss, ubit_t bit)
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{
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tss->history[tss->history_idx] = bit;
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/* simply wrap around at the end */
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tss->history_idx = (tss->history_idx + 1) % ARRAY_SIZE(tss->history);
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}
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/* append bits to history. We assume that this does NOT wrap */
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static void rx_history_add_bits(struct trau_rx_sync_state *tss, const ubit_t *bits, size_t n_bits)
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{
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unsigned int frame_bits_remaining = tss->pattern->byte_len*8 - tss->history_idx;
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OSMO_ASSERT(frame_bits_remaining >= n_bits);
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memcpy(&tss->history[tss->history_idx], bits, n_bits);
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tss->history_idx = tss->history_idx + n_bits;
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}
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/* align the history, i.e. next received bit is start of frame */
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static void rx_history_align(struct trau_rx_sync_state *tss)
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{
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ubit_t tmp[sizeof(tss->history)];
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size_t history_size = sizeof(tss->history);
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size_t pattern_bits = tss->pattern->byte_len*8;
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size_t first_bit = (history_size + tss->history_idx - pattern_bits) % history_size;
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int i;
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/* we need to shift the last received frame to the start of the history buffer;
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* do this in two steps: First copy to a local buffer on the stack, using modulo-arithmetic
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* as index into the history. Second, copy it back to history */
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for (i = 0; i < pattern_bits; i++)
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tmp[i] = tss->history[(first_bit + i) % history_size];
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memcpy(tss->history, tmp, history_size);
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tss->history_idx = 0;
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}
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enum trau_sync_state {
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WAIT_FRAME_ALIGN,
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FRAME_ALIGNED,
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/* if at least 3 consecutive frames with each at least one framing error have been received */
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FRAME_ALIGNMENT_LOST,
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};
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enum trau_sync_event {
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TRAUSYNC_E_RESET,
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/*! a buffer of bits was received (msgb with ubits) */
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TRAUSYNC_E_RX_BITS,
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};
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static const struct value_string trau_sync_event_names[] = {
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{ TRAUSYNC_E_RESET, "RESET" },
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{ TRAUSYNC_E_RX_BITS, "RX_BITS" },
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{ 0, NULL }
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};
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static void trau_sync_wait_align(struct osmo_fsm_inst *fi, uint32_t event, void *data)
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{
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struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv;
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struct ubit_buf *ubb;
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switch (event) {
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case TRAUSYNC_E_RX_BITS:
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ubb = data;
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/* append every bit individually + check if we have sync */
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while (ubb_length(ubb) > 0) {
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ubit_t bit = ubb_pull_ubit(ubb);
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int rc;
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rx_history_add_bit(tss, bit);
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rc = correlate_history_against_pattern(tss);
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if (!rc) {
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osmo_fsm_inst_state_chg(fi, FRAME_ALIGNED, 0, 0);
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/* treat remainder of input bits in correct state */
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osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, ubb);
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return;
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}
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}
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break;
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default:
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OSMO_ASSERT(0);
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}
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}
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static void trau_sync_aligned_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
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{
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struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv;
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/* dispatch aligned frame to user */
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rx_history_align(tss);
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tss->out_cb(tss->user_data, tss->history, tss->pattern->byte_len*8);
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}
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static void trau_sync_aligned(struct osmo_fsm_inst *fi, uint32_t event, void *data)
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{
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struct trau_rx_sync_state *tss = (struct trau_rx_sync_state *) fi->priv;
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struct ubit_buf *ubb;
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int rc;
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switch (event) {
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case TRAUSYNC_E_RX_BITS:
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ubb = data;
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while (ubb_length(ubb)) {
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unsigned int frame_bits_remaining = tss->pattern->byte_len*8 - tss->history_idx;
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if (ubb_length(ubb) < frame_bits_remaining) {
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/* frame not filled by this message; just add data */
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rx_history_add_bits(tss, ubb_data(ubb), ubb_length(ubb));
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ubb_pull(ubb, ubb_length(ubb));
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} else {
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/* append as many bits as are missing in the current frame */
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rx_history_add_bits(tss, ubb_data(ubb), frame_bits_remaining);
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ubb_pull(ubb, frame_bits_remaining);
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/* check if we still have frame sync */
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rc = correlate_history_against_pattern(tss);
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if (rc > 0) {
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tss->num_consecutive_errors++;
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if (tss->num_consecutive_errors >= 3) {
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tss->history_idx = 0;
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/* send NULL frame to user */
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tss->out_cb(tss->user_data, NULL, 0);
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osmo_fsm_inst_state_chg(fi, FRAME_ALIGNMENT_LOST, 1, T_SYNC);
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osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, ubb);
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return;
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}
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} else
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tss->num_consecutive_errors = 0;
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/* dispatch aligned frame to user */
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tss->out_cb(tss->user_data, tss->history, tss->history_idx);
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tss->history_idx = 0;
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}
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}
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break;
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default:
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OSMO_ASSERT(0);
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}
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}
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static void trau_sync_alignment_lost(struct osmo_fsm_inst *fi, uint32_t event, void *data)
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{
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/* we try to restore sync for some amount of time before generating an error */
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switch (event) {
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case TRAUSYNC_E_RX_BITS:
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trau_sync_wait_align(fi, event, data);
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break;
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default:
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OSMO_ASSERT(0);
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}
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}
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static void trau_sync_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *data)
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{
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switch (event) {
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case TRAUSYNC_E_RESET:
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osmo_fsm_inst_state_chg(fi, WAIT_FRAME_ALIGN, 0, 0);
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break;
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default:
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OSMO_ASSERT(0);
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}
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}
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static int trau_sync_timeout(struct osmo_fsm_inst *fi)
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{
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switch (fi->T) {
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case T_SYNC:
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/* if Tsync expires before frame synchronization is
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* again obtained the TRAU initiates sending of the
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* urgent alarm pattern described in clause 4.10.2. */
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osmo_fsm_inst_state_chg(fi, WAIT_FRAME_ALIGN, 0, 0);
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break;
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default:
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OSMO_ASSERT(0);
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}
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return 0;
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}
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static const struct osmo_fsm_state trau_sync_states[] = {
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[WAIT_FRAME_ALIGN] = {
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.name = "WAIT_FRAME_ALIGN",
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.in_event_mask = S(TRAUSYNC_E_RX_BITS),
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.out_state_mask = S(FRAME_ALIGNED),
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.action = trau_sync_wait_align,
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},
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[FRAME_ALIGNED] = {
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.name = "FRAME_ALIGNED",
|
|
.in_event_mask = S(TRAUSYNC_E_RX_BITS),
|
|
.out_state_mask = S(FRAME_ALIGNMENT_LOST) | S(WAIT_FRAME_ALIGN),
|
|
.action = trau_sync_aligned,
|
|
.onenter = trau_sync_aligned_onenter,
|
|
},
|
|
[FRAME_ALIGNMENT_LOST] = {
|
|
.name = "FRAME_ALIGNMENT_LOST",
|
|
.in_event_mask = S(TRAUSYNC_E_RX_BITS),
|
|
.out_state_mask = S(WAIT_FRAME_ALIGN) | S(FRAME_ALIGNED),
|
|
.action = trau_sync_alignment_lost,
|
|
},
|
|
};
|
|
|
|
static struct osmo_fsm trau_sync_fsm = {
|
|
.name = "trau_sync",
|
|
.states = trau_sync_states,
|
|
.num_states = ARRAY_SIZE(trau_sync_states),
|
|
.allstate_event_mask = S(TRAUSYNC_E_RESET),
|
|
.allstate_action = trau_sync_allstate,
|
|
.timer_cb = trau_sync_timeout,
|
|
.log_subsys = DLGLOBAL,
|
|
.event_names = trau_sync_event_names,
|
|
};
|
|
|
|
|
|
struct osmo_fsm_inst *
|
|
osmo_trau_sync_alloc(void *ctx, const char *name, frame_out_cb_t frame_out_cb,
|
|
enum osmo_tray_sync_pat_id pat_id, void *user_data)
|
|
{
|
|
struct trau_rx_sync_state *tss;
|
|
struct osmo_fsm_inst *fi;
|
|
|
|
if (pat_id >= ARRAY_SIZE(sync_patterns))
|
|
return NULL;
|
|
|
|
fi = osmo_fsm_inst_alloc(&trau_sync_fsm, ctx, NULL, LOGL_NOTICE, name);
|
|
if (!fi)
|
|
return NULL;
|
|
tss = talloc_zero(fi, struct trau_rx_sync_state);
|
|
if (!tss) {
|
|
osmo_fsm_inst_term(fi, OSMO_FSM_TERM_ERROR, NULL);
|
|
return NULL;
|
|
}
|
|
fi->priv = tss;
|
|
|
|
tss->out_cb = frame_out_cb;
|
|
tss->user_data = user_data;
|
|
tss->pattern = &sync_patterns[pat_id];
|
|
|
|
/* An unusued E1 timeslot normally would send an idle signal that
|
|
* has all bits set to one. In order to prevent false-positive
|
|
* synchronization on startup we set all history bits to 1, to make
|
|
* it look like a signal from an unused timeslot. */
|
|
memset(tss->history, 1, sizeof(tss->history));
|
|
|
|
return fi;
|
|
}
|
|
|
|
void osmo_trau_sync_set_pat(struct osmo_fsm_inst *fi, enum osmo_tray_sync_pat_id pat_id)
|
|
{
|
|
struct trau_rx_sync_state *tss = fi->priv;
|
|
|
|
tss->pattern = &sync_patterns[pat_id];
|
|
osmo_fsm_inst_state_chg(fi, FRAME_ALIGNMENT_LOST, 0, 0);
|
|
}
|
|
|
|
void osmo_trau_sync_rx_ubits(struct osmo_fsm_inst *fi, const ubit_t *bits, size_t n_bits)
|
|
{
|
|
struct ubit_buf ubb;
|
|
ubb_init(&ubb, bits, n_bits);
|
|
osmo_fsm_inst_dispatch(fi, TRAUSYNC_E_RX_BITS, &ubb);
|
|
}
|
|
|
|
static void __attribute__((constructor)) on_dso_load_sync(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < ARRAY_SIZE(sync_patterns); i++)
|
|
sync_pattern_register(&sync_patterns[i]);
|
|
OSMO_ASSERT(osmo_fsm_register(&trau_sync_fsm) == 0);
|
|
}
|