Do platform-dependent sub-libraries still make sense with Eio?

[Tim-ats-d]

Sorry if I'm not expressing myself well, I have a vague idea of the interoperability of Eio with other platforms for now.

For example, to access the file system, it is necessary to have an Eio.Path.t only provided by the environment object. So, I guess Mirage OS support for Eio will not provide #(cwd) and #(fs) methods in environment object. Based on this statement, does a xxx-eio-unix sub-library still make sense?

[talex5]

So, I guess Mirage OS support for Eio will not provide #(cwd) and #(fs) methods in environment object.

Eio_main.run is used on Unix-compatible systems, where you have code such as:

let main ~dir = ...

let () =
  Eio_main.run @@ fun env ->
  main ~dir:env#cwd

A unikernel wouldn't call Eio_main.run. Instead the mirage tool will generate whatever entrypoint is appropriate for the platform. e.g. there might be an Eio_xen.run function that would provide access to XenStore. The mirage-generated code would use that to get a block device, and use the block device to make a filesystem. It would then call your main function with that filesystem, e.g.

(* Generated by mirage tool *)
let () =
  Eio_xen.run @@ fun env ->
  let vda = Blkfront.connect env "vda" in
  let fs = Ext4.of_block vda in
  main ~dir:(Ext4.root fs)

[Tim-ats-d]

Ok thanks, things are clearer for me now.