Avoid warnings from Unified Runtime Level Zero adapter

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 * Removed stale `select_host_device` and `has_host_device` names from `dpctl.__all__`, which made `from dpctl import *` fail with `AttributeError` [gh-2410](https://github.com/IntelPython/dpctl/pull/2410)
 * A USM allocation that fails now drops the references held for offloaded tasks that have completed, and is attempted once more if that released anything, so that memory only waiting to be given up is not reported as unavailable [gh-2359](https://github.com/IntelPython/dpctl/pull/2359)
+* `dpctl.SyclPlatform.get_devices` no longer prints Unified Runtime warnings for `device_type="custom"` on non-OpenCL platforms, where custom devices are not supported [gh-2306](https://github.com/IntelPython/dpctl/pull/2306)
 
 ### Maintenance
 * Removed the `-fno-sycl-id-queries-fit-in-int` compile option, which none of the `dpctl` extensions need since `dpctl.tensor` moved to `dpnp` [gh-2413](https://github.com/IntelPython/dpctl/pull/2413)

dpctl/_sycl_platform.pyx

@@ -387,8 +387,10 @@ cdef class SyclPlatform(_SyclPlatform):
             device_type (str, :class:`dpctl.device_type`, optional):
                 A :class:`dpctl.device_type` enum value or a string that
                 specifies a SYCL device type. Currently, accepted values are:
-                "gpu", "cpu", "accelerator", or "all", and their equivalent
-                ``dpctl.device_type`` enumerators.
+                "gpu", "cpu", "accelerator", "automatic", "custom", or "all",
+                and their equivalent ``dpctl.device_type`` enumerators.
+                Only OpenCL platforms support custom devices; for other
+                platforms, "custom" returns an empty tuple.
                 Default: ``dpctl.device_type.all``.
 
         Returns:

dpctl/tests/test_sycl_platform.py

@@ -260,6 +260,24 @@ def test_platform_get_devices_enum_device_type():
                     assert (d.device_type == dty for d in devices)
 
 
+@pytest.mark.parametrize("dty", ["custom", device_type.custom])
+def test_platform_get_devices_custom_non_opencl(dty, capfd):
+    platforms = [
+        p
+        for p in dpctl.get_platforms()
+        if p.backend != dpctl.backend_type.opencl
+    ]
+    if not platforms:
+        pytest.skip("No non-OpenCL platforms available")
+    capfd.readouterr()
+    for p in platforms:
+        assert len(p.get_devices(device_type=dty)) == 0
+    out, err = capfd.readouterr()
+    # e.g., the Level Zero adapter warns on device_type::custom
+    assert out == ""
+    assert err == ""
+
+
 def test_platform_get_composite_devices():
     platforms = dpctl.get_platforms()
     if platforms:

libsyclinterface/include/syclinterface/dpctl_sycl_platform_interface.h

@@ -183,6 +183,9 @@ size_t DPCTLPlatform_Hash(__dpctl_keep const DPCTLSyclPlatformRef PRef);
  * @brief Returns a vector of devices associated with sycl::platform referenced
  * by DPCTLSyclPlatformRef object.
  *
+ * Only OpenCL platforms support custom devices; for other platforms,
+ * DPCTL_CUSTOM returns an empty vector.
+ *
  * @param    PRef           The DPCTLSyclPlatformRef pointer.
  * @param    DTy            A DPCTLSyclDeviceType enum value.
  * @return   A DPCTLDeviceVectorRef with devices associated with given PRef.

libsyclinterface/source/dpctl_sycl_platform_interface.cpp

@@ -304,6 +304,15 @@ DPCTLPlatform_GetDevices(__dpctl_keep const DPCTLSyclPlatformRef PRef,
         return wrap<vecTy>(DevicesVectorPtr);
     }
 
+    // Only OpenCL supports custom devices; other backends may warn when asked
+    // for them (e.g., the Unified Runtime Level Zero adapter)
+    if (DTy == DPCTLSyclDeviceType::DPCTL_CUSTOM &&
+        DPCTL_SyclBackendToDPCTLBackendType(P->get_backend()) !=
+            DPCTLSyclBackendType::DPCTL_OPENCL)
+    {
+        return wrap<vecTy>(DevicesVectorPtr);
+    }
+
     try {
         auto SyclDTy = DPCTL_DPCTLDeviceTypeToSyclDeviceType(DTy);
         auto Devices = P->get_devices(SyclDTy);