sdm/include/utils/fence.h

/*
* Copyright (c) 2019-2020, The Linux Foundation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
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*       from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
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#ifndef __FENCE_H__
#define __FENCE_H__

#include <core/buffer_sync_handler.h>
#include <unistd.h>
#include <utility>
#include <memory>
#include <string>
#include <vector>

namespace sdm {

using std::shared_ptr;
using std::string;

class Fence {
 public:
  enum class Status : int32_t {
    kSignaled = 0,
    kPending
  };

  // This class methods allow client to get access to the native file descriptor of fence object
  // during the scope of this class object. Underlying file descriptor is duped and returned to
  // the client. Duped file descriptors are closed as soon as scope ends. Client can get access
  // to multiple fences using the same scoped reference.
  class ScopedRef {
   public:
    ~ScopedRef();
    int Get(const shared_ptr<Fence> &fence);

   private:
    std::vector<int> dup_fds_ = {};
  };

  ~Fence();

  // Must be set once before using any other method of this class.
  static void Set(BufferSyncHandler *buffer_sync_handler);

  // Ownership of the file descriptor is transferred to this method.
  // Client must not close the file descriptor anymore regardless of the object creation status.
  // nullptr will be retured for invalid fd i.e. -1.
  static shared_ptr<Fence> Create(int fd);

  // Ownership of returned fd lies with caller. Caller must explicitly close the fd.
  static int Dup(const shared_ptr<Fence> &fence);

  static shared_ptr<Fence> Merge(const shared_ptr<Fence> &fence1, const shared_ptr<Fence> &fence2);

  // Wait on null fence will return success.
  static DisplayError Wait(const shared_ptr<Fence> &fence);
  static DisplayError Wait(const shared_ptr<Fence> &fence, int timeout);

  // Status check on null fence will return signaled.
  static Status GetStatus(const shared_ptr<Fence> &fence);

  static string GetStr(const shared_ptr<Fence> &fence);

 private:
  explicit Fence(int fd);
  Fence(const Fence &fence) = delete;
  Fence& operator=(const Fence &fence) = delete;
  Fence(Fence &&fence) = delete;
  Fence& operator=(Fence &&fence) = delete;
  static int Get(const shared_ptr<Fence> &fence);

  static BufferSyncHandler *buffer_sync_handler_;
  int fd_ = -1;
};

}  // namespace sdm

#endif  // __FENCE_H__