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aee4786d8e
This singleton simplifies many aspects that we struggled with before: 1. There's no need to make derived classes of Device expose the constructor as public anymore. The singleton is a friend of them, so he can call the constructor. This solves the issue with try_create_device helper neatly, hopefully for good. 2. Getting a reference of the NullDevice is now being done from this singleton, which means that NullDevice no longer needs to use its own singleton, and we can apply the try_create_device helper on it too :) 3. We can now defer registration completely after the Device constructor which means the Device constructor is merely assigning the major and minor numbers of the Device, and the try_create_device helper ensures it calls the after_inserting method immediately after construction. This creates a great opportunity to make registration more OOM-safe.
47 lines
1.0 KiB
C++
47 lines
1.0 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Singleton.h>
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#include <Kernel/Devices/DeviceManagement.h>
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#include <Kernel/Devices/NullDevice.h>
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#include <Kernel/Sections.h>
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namespace Kernel {
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UNMAP_AFTER_INIT NonnullRefPtr<NullDevice> NullDevice::must_initialize()
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{
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auto null_device_or_error = DeviceManagement::try_create_device<NullDevice>();
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// FIXME: Find a way to propagate errors
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VERIFY(!null_device_or_error.is_error());
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return null_device_or_error.release_value();
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}
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UNMAP_AFTER_INIT NullDevice::NullDevice()
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: CharacterDevice(1, 3)
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{
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}
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UNMAP_AFTER_INIT NullDevice::~NullDevice()
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{
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}
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bool NullDevice::can_read(const OpenFileDescription&, size_t) const
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{
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return true;
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}
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KResultOr<size_t> NullDevice::read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t)
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{
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return 0;
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}
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KResultOr<size_t> NullDevice::write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t buffer_size)
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{
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return buffer_size;
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}
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}
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