Kernel: Implement basic framebuffer device

This allows exposing framebuffer to userspace

kernel/include/kernel/Device/FramebufferDevice.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <kernel/Device/Device.h>
+#include <kernel/Memory/VirtualRange.h>
+
+namespace Kernel
+{
+
+	class FramebufferDevice : public CharacterDevice
+	{
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<FramebufferDevice>> create_from_boot_framebuffer();
+		~FramebufferDevice();
+
+		virtual dev_t rdev() const override { return m_rdev; }
+
+		virtual BAN::StringView name() const override { return m_name.sv(); }
+
+	protected:
+		virtual BAN::ErrorOr<size_t> read_impl(off_t, BAN::ByteSpan) override;
+		virtual BAN::ErrorOr<size_t> write_impl(off_t, BAN::ConstByteSpan) override;
+
+	private:
+		FramebufferDevice(mode_t mode, uid_t uid, gid_t gid, dev_t rdev, paddr_t paddr, uint32_t width, uint32_t height, uint32_t pitch, uint8_t bpp);
+		BAN::ErrorOr<void> initialize();
+
+		void sync_pixels(uint32_t first_pixel, uint32_t pixel_count);
+
+	private:
+		const BAN::String m_name;
+		const dev_t m_rdev;
+
+		vaddr_t			m_video_memory_vaddr { 0 };
+		const paddr_t	m_video_memory_paddr;
+		const uint32_t	m_width;
+		const uint32_t	m_height;
+		const uint32_t	m_pitch;
+		const uint8_t	m_bpp;
+
+		BAN::UniqPtr<VirtualRange> m_video_buffer;
+	};
+
+}