Tighten up LowLevelHardwareInterfaces

[flanfly]

Hi,

I'm implementing the LowLevelHardwareInterfaces interface and noticed that many of the functions don't seem to be strictly necessary. The most blatant example are PCIReadConfig* and PCIWriteConfig* as well as PCIReadVendorID and PCIReadDeviceID. If the interface would defined PCIReadConfig(address uint64) ([]byte, error) and PCIWriteConfig(address uint64, buf []byte) error all other functions could be implemented as free functions using the interface e.g.

func PCIReadConfig8(hwapi LowLevelHardwareInterfaces, d PCIDevice, off int) (uint8, error) {
    buf := make([]byte, 1)
    return buf[0], hwapi.PCIReadConfig(d, off)
}

Same applies IMO to ReadMSR vs. ReadMSRAllCores, all CPUID and SMBIOS functions, ReadPhys vs. ReadPhysBuf and both ACPI retrieval functions. In the latter case I don't see how the means of getting them matters to the consumer of the interface.

The second issue I have with the interface is performance. Especially the ReadPhysBuf function forces the implementation to copy the requested data into a user provided buffer. In my case the data is read ahead of time and it would improve memory and CPU consumption a lot if the function could just return a byte slice.

I think the following interface would suffice:

type MemoryRange struct
       Begin uint64 // included
       End uint64. // excluded
}

type LowLevelHardwareInterfaces interface {
	// cpuid.go
        CPUID(leaf uint32, sub uint32) (uint32, uint32, uint32, uint32, error)

	// e820.go
	GetReservedAreas() ([]MemoryRange, error)

	// iommu.go
	LookupIOAddress(addr uint64, regs VTdRegisters) ([]uint64, error)
	AddressRangesIsDMAProtected(first, end uint64) (bool, error)

	// msr.go
	ReadMSR(msr int64) ([]uint64, error) // value for each core

	// pci.go
	PCIDeviceList() ([]PCIDevice, error)
	PCIReadConfig(d PCIDevice, off uint64, size uint64) ([]byte, error)
	PCIWriteConfig(d PCIDevice, off int, val []byte) error

	// hostbridge.go
	ReadHostBridgeTseg() (uint32, uint32, error)
	ReadHostBridgeDPR() (DMAProtectedRange, error)

	// phys.go
	ReadPhys(addr uint64, size uint64) ([]byte, error)
	WritePhys(addr uint64, data []byte) error

	// tpm.go
	NewTPM() (*TPM, error)
	NVLocked(tpmCon *TPM) (bool, error)
	ReadNVPublic(tpmCon *TPM, index uint32) ([]byte, error)
	NVReadValue(tpmCon *TPM, index uint32, password string, size, offhandle uint32) ([]byte, error)
	ReadPCR(tpmCon *TPM, pcr uint32) ([]byte, error)

	// acpi.go
	GetACPITable(n string) ([]byte, error)

	// smbios.go
	IterateOverSMBIOSTables(n uint8, callback func(s *smbios.Structure) bool) (ret bool, err error)
}

What do you guys think? I'm willing to implement most of that as well as fix the CSS code depending on it.