1 /*
2 * Copyright (C) 2017 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 "common/vsoc/lib/screen_region_view.h"
18
19 #include <memory>
20
21 #include "common/libs/glog/logging.h"
22 #include "common/vsoc/lib/lock_guard.h"
23
24 using vsoc::layout::screen::CompositionStats;
25 using vsoc::screen::ScreenRegionView;
26
first_buffer() const27 const uint8_t* ScreenRegionView::first_buffer() const {
28 // TODO(jemoreira): Add alignments?
29 return &(this->data().buffer[0]);
30 }
31
number_of_buffers() const32 int ScreenRegionView::number_of_buffers() const {
33 auto offset_of_first_buffer =
34 const_cast<ScreenRegionView*>(this)->pointer_to_region_offset(
35 this->first_buffer());
36 size_t total_buffer_size = control_->region_size() - offset_of_first_buffer;
37 return total_buffer_size / buffer_size();
38 }
39
GetBuffer(int buffer_idx)40 void* ScreenRegionView::GetBuffer(int buffer_idx) {
41 uint8_t* buffer = const_cast<uint8_t*>(this->first_buffer());
42 return buffer + buffer_idx * this->buffer_size();
43 }
44
45 // We can use a locking protocol because we decided that the streamer should
46 // have more priority than the hwcomposer, so it's OK to block the hwcomposer
47 // waiting for the streamer to complete, while the streamer will only block on
48 // the hwcomposer when it has ran out of work to do and needs to get more from
49 // the hwcomposer.
BroadcastNewFrame(int buffer_idx,const CompositionStats * stats)50 void ScreenRegionView::BroadcastNewFrame(int buffer_idx,
51 const CompositionStats* stats) {
52 {
53 if (buffer_idx < 0 || buffer_idx >= number_of_buffers()) {
54 LOG(ERROR) << "Attempting to broadcast an invalid buffer index: "
55 << buffer_idx;
56 return;
57 }
58 auto lock_guard(make_lock_guard(&data()->bcast_lock));
59 data()->seq_num++;
60 data()->buffer_index = static_cast<int32_t>(buffer_idx);
61 if (stats) {
62 data()->stats = *stats;
63 }
64 }
65 // Signaling after releasing the lock may cause spurious wake ups.
66 // Signaling while holding the lock may cause the just-awaken listener to
67 // block immediately trying to acquire the lock.
68 // The former is less costly and slightly less likely to happen.
69 SendSignal(layout::Sides::Both, &data()->seq_num);
70 }
71
WaitForNewFrameSince(uint32_t * last_seq_num,CompositionStats * stats)72 int ScreenRegionView::WaitForNewFrameSince(uint32_t* last_seq_num,
73 CompositionStats* stats) {
74 static std::unique_ptr<RegionWorker> worker = StartWorker();
75 // It's ok to read seq_num here without holding the lock because the lock will
76 // be acquired immediately after so we'll block if necessary to wait for the
77 // critical section in BroadcastNewFrame to complete.
78 // Also, the call to WaitForSignal receives a pointer to seq_num (so the
79 // compiler should not optimize it out) and includes a memory barrier
80 // (FUTEX_WAIT).
81 while (data()->seq_num == *last_seq_num) {
82 // Don't hold the lock when waiting for a signal, will deadlock.
83 WaitForSignal(&data()->seq_num, *last_seq_num);
84 }
85
86 {
87 auto lock_guard(make_lock_guard(&data()->bcast_lock));
88 *last_seq_num = data()->seq_num;
89 if (stats) {
90 *stats = data()->stats;
91 }
92 return static_cast<int>(data()->buffer_index);
93 }
94 }
95