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Kernel: Introduce the DeviceManagement singleton

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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.
This commit is contained in:
Liav A 2021-09-11 09:19:20 +03:00 • committed by Idan Horowitz
parent 9aa6dd6b78
commit aee4786d8e
43 changed files with 244 additions and 123 deletions
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5
Kernel/Devices/MemoryDevice.h
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@ -15,16 +15,17 @@ namespace Kernel {
class MemoryDevice final : public CharacterDevice {
AK_MAKE_ETERNAL
friend class DeviceManagement;
public:
static NonnullRefPtr<MemoryDevice> must_create();
~MemoryDevice();
virtual KResultOr<Memory::Region*> mmap(Process&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
// FIXME: We expose this constructor to make try_create_device helper to work
private:
MemoryDevice();
private:
virtual StringView class_name() const override { return "MemoryDevice"; }
virtual bool can_read(const OpenFileDescription&, size_t) const override { return true; }
virtual bool can_write(const OpenFileDescription&, size_t) const override { return false; }