UEFI file systems GUIDs and firmware

Question

UEFI itself understand FAT file systems. Apple systems add support for HFS+. Is there some registrar which registers GUID codes, which are understood by firmware?

Answer 1

From the UEFI user perspective file systems GUIDs has little sense. In UEFI everything is abstracted by protocols. So the GUID of the protocol makes more sense i.e. EFI_SIMPLE_FILE_SYSTEM_PROTOCOL (GUID). If a drive handle has this protocol attached it means UEFI has a PXE-driver that supports that file system. And it is transparent for the user. Apple simply provided a PXE-driver for HFS+.

You can create your file system format, write and provide a PXE-driver for your file system and UEFI will understand it and UEFI user can have access to the file system.

So going even further, you can write a PXE-driver that will provide EFI_SIMPLE_FILE_SYSTEM_PROTOCOL for the user but the actual storage would be on the cloud for example. But UEFI user will work with your device as if it would be a regular drive.

Answer 2

I believe the most correct answer to this question would be "not really".

One of the key points of GUIDs is that you can just pick one and use it. Clearly you want interoperating components to use the same GUID for the same thing, but that is left as an exercise for the user :)

In reality, whoever creates a filesystem they expect to use within a GPT context will pick a GUID, and everyone who wants to use that filesystem will need to add the correct handling for that GUID.

So, in effect, the wikipedia entry is as good a registrar as anywhere else.