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/*
* Copyright 2019 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.
*/
#pragma once
#include <functional>
#include <optional>
#include <string>
#include <utils/Timers.h>
#include "StrongTyping.h"
namespace android::scheduler {
using ScheduleResult = std::optional<nsecs_t>;
enum class CancelResult { Cancelled, TooLate, Error };
/*
* VSyncDispatch is a class that will dispatch callbacks relative to system vsync events.
*/
class VSyncDispatch {
public:
using CallbackToken = StrongTyping<size_t, class CallbackTokenTag, Compare, Hash>;
virtual ~VSyncDispatch();
/*
* A callback that can be registered to be awoken at a given time relative to a vsync event.
* \param [in] vsyncTime: The timestamp of the vsync the callback is for.
* \param [in] targetWakeupTime: The timestamp of intended wakeup time of the cb.
* \param [in] readyTime: The timestamp of intended time where client needs to finish
* its work by.
*/
using Callback =
std::function<void(nsecs_t vsyncTime, nsecs_t targetWakeupTime, nsecs_t readyTime)>;
/*
* Registers a callback that will be called at designated points on the vsync timeline.
* The callback can be scheduled, rescheduled targeting vsync times, or cancelled.
* The token returned must be cleaned up via unregisterCallback.
*
* \param [in] callbackFn A function to schedule for callback. The resources needed to invoke
* callbackFn must have lifetimes encompassing the lifetime of the
* CallbackToken returned.
* \param [in] callbackName A human-readable, unique name to identify the callback.
* \return A token that can be used to schedule, reschedule, or cancel the
* invocation of callbackFn.
*
*/
virtual CallbackToken registerCallback(Callback, std::string callbackName) = 0;
/*
* Unregisters a callback.
*
* \param [in] token The callback to unregister.
*
*/
virtual void unregisterCallback(CallbackToken token) = 0;
/*
* Timing information about a scheduled callback
*
* @workDuration: The time needed for the client to perform its work
* @readyDuration: The time needed for the client to be ready before a vsync event.
* For external (non-SF) clients, not only do we need to account for their
* workDuration, but we also need to account for the time SF will take to
* process their buffer/transaction. In this case, readyDuration will be set
* to the SF duration in order to provide enough end-to-end time, and to be
* able to provide the ready-by time (deadline) on the callback.
* For internal clients, we don't need to add additional padding, so
* readyDuration will typically be 0.
* @earliestVsync: The targeted display time. This will be snapped to the closest
* predicted vsync time after earliestVsync.
*
* callback will be dispatched at 'workDuration + readyDuration' nanoseconds before a vsync
* event.
*/
struct ScheduleTiming {
nsecs_t workDuration = 0;
nsecs_t readyDuration = 0;
nsecs_t earliestVsync = 0;
bool operator==(const ScheduleTiming& other) const {
return workDuration == other.workDuration && readyDuration == other.readyDuration &&
earliestVsync == other.earliestVsync;
}
bool operator!=(const ScheduleTiming& other) const { return !(*this == other); }
};
/*
* Schedules the registered callback to be dispatched.
*
* The callback will be dispatched at 'workDuration + readyDuration' nanoseconds before a vsync
* event.
*
* The caller designates the earliest vsync event that should be targeted by the earliestVsync
* parameter.
* The callback will be scheduled at (workDuration + readyDuration - predictedVsync), where
* predictedVsync is the first vsync event time where ( predictedVsync >= earliestVsync ).
*
* If (workDuration + readyDuration - earliestVsync) is in the past, or if a callback has
* already been dispatched for the predictedVsync, an error will be returned.
*
* It is valid to reschedule a callback to a different time.
*
* \param [in] token The callback to schedule.
* \param [in] scheduleTiming The timing information for this schedule call
* \return The expected callback time if a callback was scheduled.
* std::nullopt if the callback is not registered.
*/
virtual ScheduleResult schedule(CallbackToken token, ScheduleTiming scheduleTiming) = 0;
/* Cancels a scheduled callback, if possible.
*
* \param [in] token The callback to cancel.
* \return A CancelResult::TooLate if the callback was already dispatched.
* A CancelResult::Cancelled if the callback was successfully cancelled.
* A CancelResult::Error if there was an pre-condition violation.
*/
virtual CancelResult cancel(CallbackToken token) = 0;
virtual void dump(std::string& result) const = 0;
protected:
VSyncDispatch() = default;
VSyncDispatch(const VSyncDispatch&) = delete;
VSyncDispatch& operator=(const VSyncDispatch&) = delete;
};
/*
* Helper class to operate on registered callbacks. It is up to user of the class to ensure
* that VsyncDispatch lifetime exceeds the lifetime of VSyncCallbackRegistation.
*/
class VSyncCallbackRegistration {
public:
VSyncCallbackRegistration(VSyncDispatch&, VSyncDispatch::Callback, std::string callbackName);
~VSyncCallbackRegistration();
VSyncCallbackRegistration(VSyncCallbackRegistration&&);
VSyncCallbackRegistration& operator=(VSyncCallbackRegistration&&);
// See documentation for VSyncDispatch::schedule.
ScheduleResult schedule(VSyncDispatch::ScheduleTiming scheduleTiming);
// See documentation for VSyncDispatch::cancel.
CancelResult cancel();
private:
std::reference_wrapper<VSyncDispatch> mDispatch;
VSyncDispatch::CallbackToken mToken;
bool mValidToken;
};
} // namespace android::scheduler
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