Fix return of component and composite device info queries

The UR_DEVICE_INFO_COMPONENT_DEVICES and UR_DEVICE_INFO_COMPOSITE_DEVICE
device info queries currently have confusing return values for all
backends.

For backends that do not support these queries, they return 0, despite
both queries being expected to return 1 or more devices, which may have
a larger type than the integral 0. To address this, these backends now
return UR_RESULT_ERROR_UNSUPPORTED_FEATURE to signal that the device
info queries are not supported by the given backend.

For the L0 backend that supports this, the case where the component
devices query has no devices, it also returns a 0 literal. Instead, this
commit changes it to report a 0-sized return value and will not write
to the return value if asked.

Signed-off-by: Larsen, Steffen <[email protected]>

Author: steffenlarsen

source/adapters/cuda/device.cpp

@@ -1077,7 +1077,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(ur_device_handle_t hDevice,
   case UR_DEVICE_INFO_COMPONENT_DEVICES:
   case UR_DEVICE_INFO_COMPOSITE_DEVICE:
     // These two are exclusive of L0.
-    return ReturnValue(0);
+    return UR_RESULT_ERROR_UNSUPPORTED_FEATURE;
   case UR_DEVICE_INFO_MAX_READ_WRITE_IMAGE_ARGS:
   case UR_DEVICE_INFO_GPU_EU_COUNT:
   case UR_DEVICE_INFO_GPU_EU_SIMD_WIDTH:

source/adapters/hip/device.cpp

@@ -849,7 +849,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(ur_device_handle_t hDevice,
   case UR_DEVICE_INFO_COMPONENT_DEVICES:
   case UR_DEVICE_INFO_COMPOSITE_DEVICE:
     // These two are exclusive of L0.
-    return ReturnValue(0);
+    return UR_RESULT_ERROR_UNSUPPORTED_FEATURE;
   case UR_DEVICE_INFO_TIMESTAMP_RECORDING_SUPPORT_EXP:
     return ReturnValue(true);
 

source/adapters/level_zero/device.cpp

@@ -891,7 +891,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(
     // First call to get SubDeviceCount.
     ZE2UR_CALL(zeDeviceGetSubDevices, (DevHandle, &SubDeviceCount, nullptr));
     if (SubDeviceCount == 0)
-      return ReturnValue(0);
+      return ReturnValue(std::nullopt);
 
     std::vector<ze_device_handle_t> SubDevs(SubDeviceCount);
     // Second call to get the actual list of devices.

source/adapters/native_cpu/device.cpp

@@ -312,7 +312,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(ur_device_handle_t hDevice,
   case UR_DEVICE_INFO_COMPONENT_DEVICES:
   case UR_DEVICE_INFO_COMPOSITE_DEVICE:
     // These two are exclusive of L0.
-    return ReturnValue(0);
+    return UR_RESULT_ERROR_UNSUPPORTED_FEATURE;
 
     CASE_UR_UNSUPPORTED(UR_DEVICE_INFO_MAX_MEMORY_BANDWIDTH);
   case UR_DEVICE_INFO_VIRTUAL_MEMORY_SUPPORT:

source/adapters/opencl/device.cpp

@@ -966,7 +966,7 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(ur_device_handle_t hDevice,
   case UR_DEVICE_INFO_COMPONENT_DEVICES:
   case UR_DEVICE_INFO_COMPOSITE_DEVICE:
     // These two are exclusive of L0.
-    return ReturnValue(0);
+    return UR_RESULT_ERROR_UNSUPPORTED_FEATURE;
   /* TODO: Check regularly to see if support is enabled in OpenCL. Intel GPU
    * EU device-specific information extensions. Some of the queries are
    * enabled by cl_intel_device_attribute_query extension, but it's not yet in

source/ur/ur.hpp

@@ -16,6 +16,7 @@
 #include <functional>
 #include <iostream>
 #include <mutex>
+#include <optional>
 #include <shared_mutex>
 #include <string>
 #include <thread>
@@ -263,6 +264,12 @@ getInfo<const char *>(size_t param_value_size, void *param_value,
   return getInfoArray(strlen(value) + 1, param_value_size, param_value,
                       param_value_size_ret, value);
 }
+
+ur_result_t getInfoEmpty(size_t param_value_size, void *param_value,
+                         size_t *param_value_size_ret) {
+  return getInfoImpl(param_value_size, param_value, param_value_size_ret, 0,
+                     0, [](void *, int, size_t) {});
+}
 } // namespace ur
 
 class UrReturnHelper {
@@ -296,6 +303,12 @@ class UrReturnHelper {
                                         param_value_size_ret, t);
   }
 
+  // Special case when there is no return value
+  ur_result_t operator()(std::nullopt_t) {
+    return ur::getInfoEmpty(param_value_size, param_value,
+                            param_value_size_ret);
+  }
+
 protected:
   size_t param_value_size;
   void *param_value;