Review changes - will be squashed later

Change service name from `gpu` to `gpumon`.
Change `dom_id` to `domid`.
Define better compatibility type.
Add pgpu_address parameter to get_pgpu_vm_compatibility.
Add helpful comments to both API functions.
Remove unused json_url and json_path.

Signed-off-by: Frederico Mazzone <frederico.mazzone@citrix.com>

gpumon/gpumon_client.ml

@@ -15,7 +15,6 @@
 open Gpumon_interface
 open Xcp_client
 
-let json_url () = "file:" ^ json_path
 let xml_url () = "file:" ^ xml_path
 
 module Client = Gpumon_interface.Client(struct

gpumon/gpumon_interface.ml

@@ -12,17 +12,24 @@
  * GNU Lesser General Public License for more details.
  *)
 
-let service_name = "gpu"
+let service_name = "gpumon"
 let queue_name = Xcp_service.common_prefix ^ service_name
-let json_path = "/var/xapi/" ^ service_name ^ ".json"
 let xml_path = "/var/xapi/" ^ service_name
 
 type debug_info = string
 
 type pgpu_address = string
 type pgpu_metadata = string
-type dom_id = int
-type vgpu_compatibility = unit (* temporarily unit, until real type is determined *)
+type domid = int
 
+type incompatibility_reason = Host_driver | Guest_driver | GPU | Other
+type compatibility = Compatible | Incompatible of incompatibility_reason list
+
+(* Get the metadata for a pGPU, given its address (PCI bus ID). *)
 external get_pgpu_metadata: debug_info -> pgpu_address -> pgpu_metadata = ""
-external get_pgpu_vm_compatibility: debug_info -> pgpu_metadata -> dom_id -> vgpu_compatibility list = ""
+
+(* Check compatibility between a VM's vGPU(s) and another pGPU. *)
+(* pgpu_address = PCI bus ID of the pGPU in which the VM is currently running. *)
+(* domid = domain ID of the VM in which the vGPU(s) is running. *)
+(* pgpu_metadata = metadata of the pGPU to check compatibility for. *)
+external get_pgpu_vm_compatibility: debug_info -> pgpu_address -> domid -> pgpu_metadata -> compatibility = ""