Use torch.device instead of current device index for BnB quantizer (#10069)

* update

* apply review suggestion

---------

Co-authored-by: Sayak Paul <[email protected]>

Author: a-r-r-o-w

src/diffusers/models/model_loading_utils.py

@@ -176,6 +176,8 @@ def load_model_dict_into_meta(
     hf_quantizer=None,
     keep_in_fp32_modules=None,
 ) -> List[str]:
+    if device is not None and not isinstance(device, (str, torch.device)):
+        raise ValueError(f"Expected device to have type `str` or `torch.device`, but got {type(device)=}.")
     if hf_quantizer is None:
         device = device or torch.device("cpu")
     dtype = dtype or torch.float32

src/diffusers/models/modeling_utils.py

@@ -836,7 +836,7 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
                         param_device = "cpu"
                     # TODO (sayakpaul,  SunMarc): remove this after model loading refactor
                     elif is_quant_method_bnb:
-                        param_device = torch.cuda.current_device()
+                        param_device = torch.device(torch.cuda.current_device())
                     state_dict = load_state_dict(model_file, variant=variant)
                     model._convert_deprecated_attention_blocks(state_dict)