Revert "Refactor kv_cache_scheme handling for quantization (#10132)" (#10935)

python/sglang/srt/layers/quantization/modelopt_quant.py

@@ -140,21 +140,11 @@ class ModelOptFp8Config(QuantizationConfig):
             # Flat format (config.json quantization_config)
             # For kv_cache, check if kv_cache_scheme exists and extract algo
             kv_cache_scheme = config.get("kv_cache_scheme")
-
-            kv_cache_type = None
-            kv_cache_bits = None
-            if isinstance(kv_cache_scheme, dict):
-                # Handles the expected format: {"type": "float", "num_bits": 8}
-                kv_cache_type = kv_cache_scheme.get("type")
-                kv_cache_bits = kv_cache_scheme.get("num_bits")
-            elif isinstance(kv_cache_scheme, str):
-                # Handles the shorthand format: "FP8"
-                if kv_cache_scheme.upper() == "FP8":
-                    kv_cache_type = "float"
-                    kv_cache_bits = 8
-
-            # Now, safely use the extracted values
-            if kv_cache_type == "float" and kv_cache_bits == 8:
+            if (
+                kv_cache_scheme
+                and kv_cache_scheme.get("type") == "float"
+                and kv_cache_scheme.get("num_bits") == 8
+            ):
                 kv_cache_quant_method = "FP8"
 
             # Map 'ignore' field to 'exclude_modules'
@@ -604,22 +594,11 @@ class ModelOptFp4Config(QuantizationConfig):
             if not kv_cache_quant_algo:
                 # For config.json format, derive from kv_cache_scheme if available
                 kv_cache_scheme = config.get("kv_cache_scheme")
-
-                kv_cache_type = None
-                kv_cache_bits = None
-                if isinstance(kv_cache_scheme, dict):
-                    # Handles the expected format: {"type": "float", "num_bits": 8}
-                    kv_cache_type = kv_cache_scheme.get("type")
-                    kv_cache_bits = kv_cache_scheme.get("num_bits")
-                elif isinstance(kv_cache_scheme, str):
-                    # Handles the shorthand format: "FP8"
-                    # We can infer the properties from the string.
-                    if kv_cache_scheme.upper() == "FP8":
-                        kv_cache_type = "float"
-                        kv_cache_bits = 8
-
-                # Now, safely use the extracted values in the original logic
-                if kv_cache_type == "float" and kv_cache_bits == 8:
+                if (
+                    kv_cache_scheme
+                    and kv_cache_scheme.get("type") == "float"
+                    and kv_cache_scheme.get("num_bits") == 8
+                ):
                     kv_cache_quant_algo = "FP8"
                 else:
                     kv_cache_quant_algo = "auto"