Method initialize_impl

kernel/kernel/ACPI/ACPI.cpp:314–451

			sum += ((uint8_t*)header)[i];
		return sum == 0;
	}

	BAN::ErrorOr<void> ACPI::initialize_impl()
	{
		auto opt_rsdp = locate_rsdp();
		if (!opt_rsdp.has_value())
			return BAN::Error::from_errno(ENODEV);
		const RSDP rsdp = opt_rsdp.release_value();

		uint32_t root_entry_count = 0;

		if (rsdp.revision >= 2)
		{
			TRY(PageTable::with_fast_page(rsdp.xsdt_address & PAGE_ADDR_MASK,
				[&]() -> BAN::ErrorOr<void>
				{
					auto& xsdt = PageTable::fast_page_as<const XSDT>(rsdp.xsdt_address % PAGE_SIZE);
					if (memcmp(xsdt.signature, "XSDT", 4) != 0)
						return BAN::Error::from_errno(ENODEV);
					if (!is_valid_std_header(&xsdt))
						return BAN::Error::from_errno(ENODEV);

					m_header_table_paddr = rsdp.xsdt_address + offsetof(XSDT, entries);
					m_entry_size = 8;
					root_entry_count = (xsdt.length - sizeof(SDTHeader)) / 8;
					return {};
				}
			));
		}
		else
		{
			TRY(PageTable::with_fast_page(rsdp.rsdt_address & PAGE_ADDR_MASK,
				[&]() -> BAN::ErrorOr<void>
				{
					auto& rsdt = PageTable::fast_page_as<const RSDT>(rsdp.rsdt_address % PAGE_SIZE);
					if (memcmp(rsdt.signature, "RSDT", 4) != 0)
						return BAN::Error::from_errno(ENODEV);
					if (!is_valid_std_header(&rsdt))
						return BAN::Error::from_errno(ENODEV);

					m_header_table_paddr = rsdp.rsdt_address + offsetof(RSDT, entries);
					m_entry_size = 4;
					root_entry_count = (rsdt.length - sizeof(SDTHeader)) / 4;
					return {};
				}
			));
		}

		size_t needed_pages = range_page_count(m_header_table_paddr, root_entry_count * m_entry_size);
		m_header_table_vaddr = PageTable::kernel().reserve_free_contiguous_pages(needed_pages, KERNEL_OFFSET);
		ASSERT(m_header_table_vaddr);

		m_header_table_vaddr += m_header_table_paddr % PAGE_SIZE;

		PageTable::kernel().map_range_at(
			m_header_table_paddr & PAGE_ADDR_MASK,
			m_header_table_vaddr & PAGE_ADDR_MASK,
			needed_pages * PAGE_SIZE,