Add symmetric support for containers with legacy DLPack support

For legacy containers, support device=(kDLCPU, 0) as well as
oneAPI device.

Author: oleksandr-pavlyk

dpctl/tensor/_dlpack.pyx

@@ -985,7 +985,8 @@ def from_dlpack(x, /, *, device=None, copy=None):
             returned by :attr:`dpctl.tensor.usm_ndarray.device`, or a
             2-tuple matching the format of the output of the ``__dlpack_device__``
             method, an integer enumerator representing the device type followed by
-            an integer representing the index of the device.
+            an integer representing the index of the device. The only supported
+            :enum:`dpctl.tensor.DLDeviceType` types are "kDLCPU" and "kDLOneAPI".
             Default: ``None``.
         copy (bool, optional)
             Boolean indicating whether or not to copy the input.
@@ -1034,6 +1035,7 @@ def from_dlpack(x, /, *, device=None, copy=None):
 
             C = Container(dpt.linspace(0, 100, num=20, dtype="int16"))
             X = dpt.from_dlpack(C)
+            Y = dpt.from_dlpack(C, device=(dpt.DLDeviceType.kDLCPU, 0))
 
     """
     dlpack_attr = getattr(x, "__dlpack__", None)
@@ -1070,6 +1072,7 @@ def from_dlpack(x, /, *, device=None, copy=None):
     saved_exception = None
     # First DLPack version supporting dl_device, and copy
     requested_ver = (1, 0)
+    cpu_dev = (device_CPU, 0)
     try:
         # setting max_version to minimal version that supports dl_device/copy keywords
         dlpack_capsule = dlpack_attr(
@@ -1105,16 +1108,35 @@ def from_dlpack(x, /, *, device=None, copy=None):
             # we can only support importing to OneAPI devices
             # from host, or from another oneAPI device
             is_supported_x_dldev = (
-                x_dldev == (device_CPU, 0) or
+                x_dldev == cpu_dev or
                 (x_dldev[0] == device_OneAPI)
             )
-            if is_supported_x_dldev and dl_device[0] == device_OneAPI:
+            is_supported_dl_device = (
+                dl_device == cpu_dev or
+                dl_device[0] == device_OneAPI
+            )
+            if is_supported_x_dldev and is_supported_dl_device:
                 dlpack_capsule = dlpack_attr()
-                host_blob = from_dlpack_capsule(dlpack_capsule)
+                blob = from_dlpack_capsule(dlpack_capsule)
             else:
                 raise BufferError(f"Can not import to requested device {dl_device}")
             dev = _create_device(device, dl_device)
-            return _to_usm_ary_from_host_blob(host_blob, dev)
+            if x_dldev == cpu_dev and dl_device == cpu_dev:
+                # both source and destion are CPU
+                return blob
+            elif x_dldev == cpu_dev:
+                # source is CPU, destingation is oneAPI
+                return _to_usm_ary_from_host_blob(blob, dev)
+            elif dl_device == cpu_dev:
+                # source is oneAPI, destination is CPU
+                cpu_caps = blob.__dlpack__(
+                    max_version=get_build_dlpack_version(),
+                    dl_device=cpu_dev
+                )
+                return from_dlpack_capsule(cpu_caps)
+            else:
+                import dpctl.tensor as dpt
+                return dpt.asarray(blob, device=dev)
         elif got_buffer_error:
             # we are here, because dlpack_attr could not deal with requested dl_device,
             # or copying was required
@@ -1126,13 +1148,13 @@ def from_dlpack(x, /, *, device=None, copy=None):
             if dl_device[0] != device_OneAPI:
                 raise BufferError(f"Can not import to requested device {dl_device}")
             x_dldev = dlpack_dev_attr()
-            if x_dldev == (device_CPU, 0):
+            if x_dldev == cpu_dev:
                 dlpack_capsule = dlpack_attr()
                 host_blob = from_dlpack_capsule(dlpack_capsule)
             else:
                 dlpack_capsule = dlpack_attr(
                     max_version=requested_ver,
-                    dl_device=(device_CPU, 0),
+                    dl_device=cpu_dev,
                     copy=copy
                 )
                 host_blob = from_dlpack_capsule(dlpack_capsule)