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/*
* Copyright 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "sco_connection.h"
#include <hci/hci_packets.h>
#include <os/log.h>
#include <vector>
using namespace rootcanal;
using namespace bluetooth::hci;
bool ScoConnectionParameters::IsExtended() {
uint16_t legacy = (uint16_t)SynchronousPacketTypeBits::HV1_ALLOWED |
(uint16_t)SynchronousPacketTypeBits::HV2_ALLOWED |
(uint16_t)SynchronousPacketTypeBits::HV3_ALLOWED;
uint16_t edr = (uint16_t)SynchronousPacketTypeBits::NO_2_EV3_ALLOWED |
(uint16_t)SynchronousPacketTypeBits::NO_3_EV3_ALLOWED |
(uint16_t)SynchronousPacketTypeBits::NO_2_EV5_ALLOWED |
(uint16_t)SynchronousPacketTypeBits::NO_3_EV5_ALLOWED;
return ((packet_type ^ edr) & ~legacy) != 0;
}
std::optional<ScoLinkParameters> ScoConnectionParameters::GetLinkParameters() {
// Coding conversion.
uint8_t air_coding_to_air_mode[] = {
0x02, // CVSD
0x00, // u-law
0x01, // A-law
0x03, // transparent data
};
// Prioritize eSCO connections.
// Packets HV1, HV2, HV3 are tested in a second phase.
struct Packet {
unsigned length;
unsigned slots;
Packet(unsigned length, unsigned slots) : length(length), slots(slots) {}
};
std::vector<Packet> accepted_packets;
accepted_packets.push_back(Packet(0, 1)); // POLL/NULL
if (packet_type & (uint16_t)SynchronousPacketTypeBits::EV3_ALLOWED)
accepted_packets.push_back(Packet(30, 1));
if (packet_type & (uint16_t)SynchronousPacketTypeBits::EV4_ALLOWED)
accepted_packets.push_back(Packet(120, 3));
if (packet_type & (uint16_t)SynchronousPacketTypeBits::EV5_ALLOWED)
accepted_packets.push_back(Packet(180, 3));
if ((packet_type & (uint16_t)SynchronousPacketTypeBits::NO_2_EV3_ALLOWED) ==
0)
accepted_packets.push_back(Packet(60, 1));
if ((packet_type & (uint16_t)SynchronousPacketTypeBits::NO_3_EV3_ALLOWED) ==
0)
accepted_packets.push_back(Packet(360, 3));
if ((packet_type & (uint16_t)SynchronousPacketTypeBits::NO_2_EV5_ALLOWED) ==
0)
accepted_packets.push_back(Packet(90, 1));
if ((packet_type & (uint16_t)SynchronousPacketTypeBits::NO_3_EV5_ALLOWED) ==
0)
accepted_packets.push_back(Packet(540, 3));
// Ignore empty bandwidths for now.
if (transmit_bandwidth == 0 || receive_bandwidth == 0) {
LOG_WARN("eSCO transmissions with null bandwidths are not supported");
return {};
}
// Bandwidth usage of the optimal selection.
double best_bandwidth_usage = 1.0;
std::optional<ScoLinkParameters> best_parameters = {};
// Explore all packet combinations, select the valid one
// with smallest actual bandwidth usage.
for (auto tx : accepted_packets) {
if (tx.length == 0) continue;
unsigned tx_max_interval = (1600 * tx.length) / transmit_bandwidth;
for (auto rx : accepted_packets) {
if (rx.length == 0) continue;
LOG_INFO("Testing combination %u/%u : %u/%u", tx.length, tx.slots,
rx.length, rx.slots);
unsigned rx_max_interval = (1600 * rx.length) / receive_bandwidth;
// Choose the best interval satisfying both.
unsigned transmission_interval =
std::min(tx_max_interval, rx_max_interval);
transmission_interval -= transmission_interval % 2;
transmission_interval = std::min(transmission_interval, 254u);
LOG_INFO("Transmission interval: %u slots", transmission_interval);
// Compute retransmission window.
unsigned retransmission_window =
retransmission_effort ==
(uint8_t)RetransmissionEffort::NO_RETRANSMISSION
? 0
: retransmission_effort ==
(uint8_t)RetransmissionEffort::OPTIMIZED_FOR_POWER
? rx.slots + tx.slots
: retransmission_effort ==
(uint8_t)RetransmissionEffort::OPTIMIZED_FOR_LINK_QUALITY
? 2 * (rx.slots + tx.slots)
: 0;
LOG_INFO("Retransmission window: %u slots", retransmission_window);
// Compute transmission window and validate latency.
unsigned transmission_window =
tx.slots + rx.slots + retransmission_window;
// Validate window.
if (transmission_window > transmission_interval)
// Oops
continue;
// Compute and validate latency.
unsigned latency = (transmission_window * 1250) / 2;
LOG_INFO("Latency: %u us (max %u us)", latency, max_latency * 1000u);
if (latency > (1000 * max_latency))
// Oops
continue;
// We got a valid configuration.
// Evaluate the actual bandwidth usage.
double bandwidth_usage =
(double)transmission_window / (double)transmission_interval;
if (bandwidth_usage <= best_bandwidth_usage) {
LOG_INFO("Valid combination!");
uint16_t tx_packet_length =
(transmit_bandwidth * transmission_interval + 1600 - 1) / 1600;
uint16_t rx_packet_length =
(receive_bandwidth * transmission_interval + 1600 - 1) / 1600;
uint8_t air_coding = voice_setting & 0x3;
best_bandwidth_usage = bandwidth_usage;
best_parameters = {
(uint8_t)transmission_interval,
(uint8_t)retransmission_window,
rx_packet_length,
tx_packet_length,
air_coding_to_air_mode[air_coding],
true,
};
}
}
}
if (best_parameters.has_value()) {
return best_parameters;
}
// Parameter negotiation for SCO connections:
// Check packet types and validate bandwidth and latency requirements.
if (retransmission_effort ==
(uint8_t)RetransmissionEffort::OPTIMIZED_FOR_POWER ||
retransmission_effort ==
(uint8_t)RetransmissionEffort::OPTIMIZED_FOR_LINK_QUALITY) {
LOG_WARN("SCO Retransmission effort must be None or Don't care");
return {};
}
uint8_t transmission_interval;
uint16_t packet_length;
unsigned latency = 1250;
uint8_t air_coding = voice_setting & 0x3;
if (max_latency != 0xffff && max_latency < latency) {
LOG_WARN("SCO Max latency must be less than 1250 us");
return {};
}
if (packet_type & (uint16_t)SynchronousPacketTypeBits::HV3_ALLOWED) {
transmission_interval = 6;
packet_length = 30;
} else if (packet_type & (uint16_t)SynchronousPacketTypeBits::HV2_ALLOWED) {
transmission_interval = 4;
packet_length = 20;
} else if (packet_type & (uint16_t)SynchronousPacketTypeBits::HV1_ALLOWED) {
transmission_interval = 2;
packet_length = 10;
} else {
LOG_WARN("No SCO packet type enabled");
return {};
}
best_parameters = {
transmission_interval,
0,
packet_length,
packet_length,
air_coding_to_air_mode[air_coding],
false,
};
return best_parameters;
}
bool ScoConnection::NegotiateLinkParameters(
ScoConnectionParameters const& peer) {
if (peer.transmit_bandwidth != 0xffff &&
peer.transmit_bandwidth != parameters_.receive_bandwidth) {
LOG_WARN("Transmit bandwidth requirements cannot be met");
return false;
}
if (state_ == SCO_STATE_SENT_ESCO_CONNECTION_REQUEST &&
peer.receive_bandwidth != 0xffff &&
peer.receive_bandwidth != parameters_.transmit_bandwidth) {
LOG_WARN("Receive bandwidth requirements cannot be met");
return false;
}
if (peer.voice_setting != parameters_.voice_setting) {
LOG_WARN("Voice setting requirements cannot be met");
LOG_WARN("Remote voice setting: 0x%04x",
static_cast<unsigned>(parameters_.voice_setting));
LOG_WARN("Local voice setting: 0x%04x",
static_cast<unsigned>(peer.voice_setting));
return false;
}
uint16_t packet_type = (peer.packet_type & parameters_.packet_type) & 0x3f;
packet_type |= (peer.packet_type | parameters_.packet_type) & 0x3c0;
if (packet_type == 0x3c0) {
LOG_WARN("Packet type requirements cannot be met");
LOG_WARN("Remote packet type: 0x%04x",
static_cast<unsigned>(parameters_.packet_type));
LOG_WARN("Local packet type: 0x%04x",
static_cast<unsigned>(peer.packet_type));
return false;
}
uint16_t max_latency =
peer.max_latency == 0xffff ? parameters_.max_latency
: parameters_.max_latency == 0xffff
? peer.max_latency
: std::min(peer.max_latency, parameters_.max_latency);
uint8_t retransmission_effort;
if (state_ == SCO_STATE_SENT_SCO_CONNECTION_REQUEST)
retransmission_effort = (uint8_t)RetransmissionEffort::NO_RETRANSMISSION;
else if (peer.retransmission_effort == parameters_.retransmission_effort ||
peer.retransmission_effort ==
(uint8_t)RetransmissionEffort::DO_NOT_CARE)
retransmission_effort = parameters_.retransmission_effort;
else if (parameters_.retransmission_effort ==
(uint8_t)RetransmissionEffort::DO_NOT_CARE)
retransmission_effort = peer.retransmission_effort;
else if (peer.retransmission_effort ==
(uint8_t)RetransmissionEffort::NO_RETRANSMISSION ||
parameters_.retransmission_effort ==
(uint8_t)RetransmissionEffort::NO_RETRANSMISSION) {
LOG_WARN("Retransmission effort requirements cannot be met");
LOG_WARN("Remote retransmission effort: 0x%02x",
static_cast<unsigned>(parameters_.retransmission_effort));
LOG_WARN("Local retransmission effort: 0x%04x",
static_cast<unsigned>(peer.retransmission_effort));
return false;
} else {
retransmission_effort = (uint8_t)RetransmissionEffort::OPTIMIZED_FOR_POWER;
}
ScoConnectionParameters negotiated_parameters = {
parameters_.transmit_bandwidth,
parameters_.receive_bandwidth,
max_latency,
parameters_.voice_setting,
retransmission_effort,
packet_type};
auto link_parameters = negotiated_parameters.GetLinkParameters();
if (link_parameters.has_value()) {
link_parameters_ = link_parameters.value();
LOG_INFO("Negotiated link parameters for SCO connection:");
LOG_INFO(" Transmission interval: %u slots",
static_cast<unsigned>(link_parameters_.transmission_interval));
LOG_INFO(" Retransmission window: %u slots",
static_cast<unsigned>(link_parameters_.retransmission_window));
LOG_INFO(" RX packet length: %u bytes",
static_cast<unsigned>(link_parameters_.rx_packet_length));
LOG_INFO(" TX packet length: %u bytes",
static_cast<unsigned>(link_parameters_.tx_packet_length));
LOG_INFO(" Air mode: %u",
static_cast<unsigned>(link_parameters_.air_mode));
} else {
LOG_WARN("Failed to derive link parameters");
}
return link_parameters.has_value();
}
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