[Linaro-uefi] Complete ATA stack in UEFI/EDK2

Hi All,

I have few doubts in SATA stack.

I have seen at some places that in UEFI/EDK2, The complete ATA stack should be like:

IdeControllerDxe +

AtaAtapiPassThru +

AtaBus +

ScsiBus +

ScsiDisk +

PartitionDriver +

Fat

What is the role of "ScsiBus + ScsiDisk" in this stack?

Complete AHCI specific code is there in "AtaAtapiPassThru"? Is this code AHCI 1.3 spec compliant?

Then why ScSi bus layer is required?

Thanks and Regards,

Shaveta