sdk/lib/driver/component/cpp/internal/driver_server.h

// Copyright 2023 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_DRIVER_COMPONENT_CPP_INTERNAL_DRIVER_SERVER_H_
#define LIB_DRIVER_COMPONENT_CPP_INTERNAL_DRIVER_SERVER_H_

#include <fidl/fuchsia.driver.framework/cpp/driver/wire.h>
#include <fidl/fuchsia.driver.framework/cpp/type_conversions.h>
#include <lib/driver/component/cpp/driver_base.h>
#include <lib/driver/component/cpp/internal/concepts.h>
#include <lib/driver/component/cpp/prepare_stop_completer.h>
#include <lib/driver/component/cpp/start_completer.h>
#include <lib/driver/logging/cpp/logger.h>
#include <lib/driver/symbols/symbols.h>

namespace fdf_internal {

// This will shim a |DriverBase| based driver with the new FIDL based registration.
template <IsDriver DriverBaseImpl>
class DriverServer final : public fdf::WireServer<fuchsia_driver_framework::Driver> {
 public:
  // Initialize the fuchsia_driver_framework::Driver server.
  static void* initialize(fdf_handle_t server_handle) {
    fdf_dispatcher_t* dispatcher = fdf_dispatcher_get_current_dispatcher();
    DriverServer* driver_server = new DriverServer(dispatcher, server_handle);
    return driver_server;
  }

  // Destroy the fuchsia_driver_framework::Driver server.
  static void destroy(void* token) {
    DriverServer* driver_server = static_cast<DriverServer*>(token);
    delete driver_server;
  }

  DriverServer(fdf_dispatcher_t* dispatcher, fdf_handle_t server_handle) : dispatcher_(dispatcher) {
    binding_.emplace(dispatcher_,
                     fdf::ServerEnd<fuchsia_driver_framework::Driver>(fdf::Channel(server_handle)),
                     this, fidl::kIgnoreBindingClosure);
  }

  virtual ~DriverServer() {
    if (driver_) {
      if (!complete_start_call_) {
        FDF_LOGL(WARNING, driver_->logger(),
                 "Driver server invoking Stop() hook before Start() is complete");
      }
      driver_->Stop();
    }
  }

  void Start(StartRequestView request, fdf::Arena& arena,
             StartCompleter::Sync& completer) override {
    driver_ = std::make_unique<DriverBaseImpl>(fidl::ToNatural(request->start_args),
                                               fdf::UnownedSynchronizedDispatcher(dispatcher_));

    fdf::StartCompleter start_completer(
        [reply_arena = std::move(arena), reply_completer = completer.ToAsync()](
            zx::result<> result) mutable { reply_completer.buffer(reply_arena).Reply(result); });

    // Post a task to do this so that the WireServerDispatcher, the caller of this method,
    // can clean up correctly. Otherwise the destruction of the arena from the callback could
    // run too early, causing use-after-frees during the cleanup of the request.
    async::PostTask(fdf_dispatcher_get_async_dispatcher(dispatcher_),
                    [this, inner_completer = std::move(start_completer)]() mutable {
                      zx::result<> result = driver_->RunInitMethods();
                      if (result.is_error()) {
                        inner_completer(result.take_error());
                        return;
                      }
                      driver_->Start(std::move(inner_completer));
                      complete_start_call_ = true;
                    });
  }

  void Stop(fdf::Arena& arena, StopCompleter::Sync& completer) override {
    ZX_ASSERT(driver_);
    driver_->PrepareStop(fdf::PrepareStopCompleter([this](zx::result<> result) { StopBinding(); }));
  }

  void handle_unknown_method(fidl::UnknownMethodMetadata<fuchsia_driver_framework::Driver> metadata,
                             fidl::UnknownMethodCompleter::Sync& completer) override {
    if (driver_) {
      FDF_LOGL(INFO, driver_->logger(), "fdf::Driver server received unknown method.");
    }
  }

  void* GetDriverBaseImpl() {
    if (driver_) {
      return driver_.get();
    }

    return nullptr;
  }

 private:
  void StopBinding() {
    if (fdf_dispatcher_get_current_dispatcher() == dispatcher_) {
      binding_.reset();
      return;
    }

    async::PostTask(fdf_dispatcher_get_async_dispatcher(dispatcher_),
                    [this]() { binding_.reset(); });
  }

  fdf_dispatcher_t* dispatcher_;

  // TODO(b/42081095): Remove this and the warning message once we finish debugging shutdown flakes.
  bool complete_start_call_ = false;

  std::optional<fdf::ServerBinding<fuchsia_driver_framework::Driver>> binding_;
  std::unique_ptr<fdf::DriverBase> driver_;
};

}  // namespace fdf_internal

#endif  // LIB_DRIVER_COMPONENT_CPP_INTERNAL_DRIVER_SERVER_H_