1 /*
2 * Copyright 2023 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "hal/link_clocker.h"
18
19 #include <bluetooth/log.h>
20
21 #include <algorithm>
22
23 #include "common/time_util.h"
24
25 namespace bluetooth::hal {
26
27 static class : public ReadClockHandler {
OnEvent(uint32_t,uint32_t)28 void OnEvent(uint32_t, uint32_t) override {}
29 } g_empty_handler;
30
31 static std::atomic<ReadClockHandler*> g_read_clock_handler = &g_empty_handler;
32
Register(ReadClockHandler * handler)33 void LinkClocker::Register(ReadClockHandler* handler) {
34 g_read_clock_handler = handler;
35 }
36
Unregister()37 void LinkClocker::Unregister() {
38 g_read_clock_handler = &g_empty_handler;
39 }
40
OnHciEvent(const HciPacket & packet)41 void LinkClocker::OnHciEvent(const HciPacket& packet) {
42 const int HCI_CMD_READ_CLOCK = 0x1407;
43 const int HCI_EVT_COMMAND_COMPLETE = 0x0e;
44
45 // HCI Event [Core 4.E.5.4.4]
46 // | [0] Event Code
47 // | [1] Parameter Total Length
48 // | [2+] Parameters
49
50 if (packet.size() < 2) return;
51
52 const uint8_t* payload = packet.data() + 2;
53 size_t payload_length = std::min(size_t(packet[1]), packet.size() - 2);
54 int event_code = packet[0];
55
56 if (event_code != HCI_EVT_COMMAND_COMPLETE) return;
57
58 // HCI Command Complete Event [Core 4.E.7.7.14]
59 // | [0] Num_HCI_Command_Packets, Ignored
60 // | [1..2] Command_Opcode, catch `HCI_LE_Set_CIG_Parameters`
61 // | [3+] Return Parameters
62
63 if (payload_length < 3) return;
64
65 uint16_t op_code = payload[1] | (payload[2] << 8);
66 const uint8_t* parameters = payload + 3;
67 size_t parameters_length = payload_length - 3;
68
69 if (op_code != HCI_CMD_READ_CLOCK) return;
70
71 // HCI Read Clock return parameters [Core 4.E.7.5.6]
72 // | [0] Status, 0 when OK
73 // | [1..2] Connection_handle
74 // | [3..6] Clock (28-bits meaningful)
75 // | [7..8] Accuracy
76
77 if (parameters_length < 9) return;
78
79 uint8_t status = parameters[0];
80
81 if (status != 0) return;
82
83 uint32_t bt_clock = ((uint32_t)parameters[3] << 0) | ((uint32_t)parameters[4] << 8) |
84 ((uint32_t)parameters[5] << 16) | ((uint32_t)parameters[6] << 24);
85
86 // The connection handle is ignored as we are reading the local clock
87 // (Which_Clock parameter is 0).
88 // The reason the read clock measurement is extracted here is that
89 // getting the local timestamp from the bound gd HCI event callback
90 // adds jitter.
91
92 unsigned timestamp_us = bluetooth::common::time_get_audio_server_tick_us();
93
94 (*g_read_clock_handler).OnEvent(timestamp_us, bt_clock << 4);
95 }
96
__anon704ccef00202() 97 const ModuleFactory LinkClocker::Factory = ModuleFactory([]() { return new LinkClocker(); });
98
99 } // namespace bluetooth::hal
100