1 /*
2  * Copyright 2019 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 #pragma once
18 
19 #include <utils/Timers.h>
20 #include "VSyncDispatch.h"
21 
22 namespace android::scheduler {
23 /*
24  * VSyncTracker is an interface for providing estimates on future Vsync signal times based on
25  * historical vsync timing data.
26  */
27 class VSyncTracker {
28 public:
29     virtual ~VSyncTracker();
30 
31     /*
32      * Adds a known timestamp from a vsync timing source (HWVsync signal, present fence)
33      * to the model.
34      *
35      * \param [in] timestamp    The timestamp when the vsync signal was.
36      * \return                  True if the timestamp was consistent with the internal model,
37      *                          False otherwise
38      */
39     virtual bool addVsyncTimestamp(nsecs_t timestamp) = 0;
40 
41     /*
42      * Access the next anticipated vsync time such that the anticipated time >= timePoint.
43      * This will always give the best accurate at the time of calling; multiple
44      * calls with the same timePoint might give differing values if the internal model
45      * is updated.
46      *
47      * \param [in] timePoint    The point in time after which to estimate a vsync event.
48      * \return                  A prediction of the timestamp of a vsync event.
49      */
50     virtual nsecs_t nextAnticipatedVSyncTimeFrom(nsecs_t timePoint) const = 0;
51 
52     /*
53      * The current period of the vsync signal.
54      *
55      * \return  The current period of the vsync signal
56      */
57     virtual nsecs_t currentPeriod() const = 0;
58 
59     /*
60      * Inform the tracker that the period is changing and the tracker needs to recalibrate itself.
61      *
62      * \param [in] period   The period that the system is changing into.
63      */
64     virtual void setPeriod(nsecs_t period) = 0;
65 
66     /* Inform the tracker that the samples it has are not accurate for prediction. */
67     virtual void resetModel() = 0;
68 
69     virtual void dump(std::string& result) const = 0;
70 
71 protected:
72     VSyncTracker(VSyncTracker const&) = delete;
73     VSyncTracker& operator=(VSyncTracker const&) = delete;
74     VSyncTracker() = default;
75 };
76 
77 } // namespace android::scheduler
78