Function acpi::parse_rsdp

pub unsafe fn parse_rsdp<H>(
    handler: &mut H, 
    rsdp_address: usize
) -> Result<Acpi, AcpiError> where
    H: AcpiHandler, 

This is the entry point of acpi if you have the physical address of the RSDP. It maps the RSDP, works out what version of ACPI the hardware supports, and passes the physical address of the RSDT/XSDT to parse_rsdt.