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ladybird/Kernel/Devices/NullDevice.h

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Meta: Add license header to source files As suggested by Joshua, this commit adds the 2-clause BSD license as a comment block to the top of every source file. For the first pass, I've just added myself for simplicity. I encourage everyone to add themselves as copyright holders of any file they've added or modified in some significant way. If I've added myself in error somewhere, feel free to replace it with the appropriate copyright holder instead. Going forward, all new source files should include a license header.
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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
Everything: Move to SPDX license identifiers in all files. SPDX License Identifiers are a more compact / standardized way of representing file license information. See: https://spdx.dev/resources/use/#identifiers This was done with the `ambr` search and replace tool. ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
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* SPDX-License-Identifier: BSD-2-Clause
Meta: Add license header to source files As suggested by Joshua, this commit adds the 2-clause BSD license as a comment block to the top of every source file. For the first pass, I've just added myself for simplicity. I encourage everyone to add themselves as copyright holders of any file they've added or modified in some significant way. If I've added myself in error somewhere, feel free to replace it with the appropriate copyright holder instead. Going forward, all new source files should include a license header.
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*/
Add basic character device support. Start with null and zero.
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#pragma once
Kernel: Standardize the header include style to 'include <Kernel/...>' This is the overwhelming standard in the project, but there were some cases in the kernel which were not following it, lets fix those cases!
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#include <Kernel/Devices/CharacterDevice.h>
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Kernel: Move all code into the Kernel namespace
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namespace Kernel {
Add basic character device support. Start with null and zero.
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class NullDevice final : public CharacterDevice {
Kernel: Introduce the DeviceManagement singleton 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.
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friend class DeviceManagement;
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public:
Implement a basic way for read() to block. FileHandle gets a hasDataAvailableForRead() getter. If this returns true in sys$read(), the task will block(BlockedRead) + yield. The fd blocked on is stored in Task::m_fdBlockedOnRead. The scheduler then looks at the state of that fd during the unblock phase. This makes "sh" restful. :^) There's still some problem with the kernel not surviving the colonel task getting scheduled. I need to figure that out and fix it.
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virtual ~NullDevice() override;
Add basic character device support. Start with null and zero.
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Kernel: Make self-contained locking smart pointers their own classes Until now, our kernel has reimplemented a number of AK classes to provide automatic internal locking: - RefPtr - NonnullRefPtr - WeakPtr - Weakable This patch renames the Kernel classes so that they can coexist with the original AK classes: - RefPtr => LockRefPtr - NonnullRefPtr => NonnullLockRefPtr - WeakPtr => LockWeakPtr - Weakable => LockWeakable The goal here is to eventually get rid of the Lock* classes in favor of using external locking.
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static NonnullLockRefPtr<NullDevice> must_initialize();
Kernel: Make sure processes always start out with fds 0, 1 and 2 open. If we don't have a TTY for the process, fall back to /dev/null.
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Kernel: Make /proc/PID/fds display something useful for character devices.
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private:
Kernel: Introduce the DeviceManagement singleton 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.
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NullDevice();
Kernel: Make /proc/PID/fds display something useful for character devices.
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// ^CharacterDevice
Kernel: Replace KResult and KResultOr<T> with Error and ErrorOr<T> We now use AK::Error and AK::ErrorOr<T> in both kernel and userspace! This was a slightly tedious refactoring that took a long time, so it's not unlikely that some bugs crept in. Nevertheless, it does pass basic functionality testing, and it's just real nice to finally see the same pattern in all contexts. :^)
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virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
Everywhere: Run clang-format
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virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override;
virtual bool can_write(OpenFileDescription const&, u64) const override { return true; }
virtual bool can_read(OpenFileDescription const&, u64) const override;
Kernel: Use `operator ""sv` in all class_name() implementations Previously there was a mix of returning plain strings and returning explicit string views using `operator ""sv`. This change switches them all to standardized on `operator ""sv` as it avoids a call to strlen.
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virtual StringView class_name() const override { return "NullDevice"sv; }
Kernel: Make NullDevice (/dev/null) seekable
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virtual bool is_seekable() const override { return true; }
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};
Kernel: Move all code into the Kernel namespace
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}
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