Kernel: Split I2C functionality from IntelNativeDisplayConnector code

Splitting the I2C-related code lets the DisplayConnector code to utilize
I2C operations without caring about the specific details of the hardware
and allow future expansion of the driver to other newer generations
sharing the same GMBus code.

We should require a timeout for GMBus operations always, because faulty
hardware could let us just spin forever. Also, if nothing is listening
to the bus (which should result in a NAK), we could also spin forever.

Kernel/Graphics/Intel/Auxiliary/GMBusConnector.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefPtr.h>
+#include <AK/Try.h>
+#include <AK/Types.h>
+#include <Kernel/Locking/Spinlock.h>
+#include <Kernel/Memory/TypedMapping.h>
+
+namespace Kernel {
+
+struct [[gnu::packed]] GMBusRegisters {
+    u32 clock;
+    u32 command;
+    u32 status;
+    u32 data;
+};
+
+enum class GMBusStatus;
+
+class GMBusConnector {
+public:
+    enum PinPair : u8 {
+        None = 0,
+        DedicatedControl = 1,
+        DedicatedAnalog = 0b10,
+        IntegratedDigital = 0b11,
+        sDVO = 0b101,
+        Dconnector = 0b111,
+    };
+
+public:
+    static ErrorOr<NonnullOwnPtr<GMBusConnector>> create_with_physical_address(PhysicalAddress gmbus_start_address);
+
+    ErrorOr<void> write(unsigned address, u32 data);
+    ErrorOr<void> read(unsigned address, u8* buf, size_t length);
+    void set_default_rate();
+
+private:
+    void set_pin_pair(PinPair pin_pair);
+
+    bool wait_for(GMBusStatus desired_status, size_t milliseconds_timeout);
+
+    explicit GMBusConnector(Memory::TypedMapping<GMBusRegisters volatile>);
+    Spinlock<LockRank::None> m_access_lock;
+    Memory::TypedMapping<GMBusRegisters volatile> m_gmbus_registers;
+};
+}