Arm backend: Add docstrings to compile specs (#15886)

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

Signed-off-by: Sebastian Larsson <sebastian.larsson@arm.com>

Author: Sebastian-Larsson

backends/arm/ethosu/compile_spec.py

@@ -15,16 +15,7 @@
 
 
 class EthosUCompileSpec(ArmCompileSpec):
-    """
-    Compile spec for Ethos-U NPU.
-
-    Args:
-        target: Ethos-U accelerator configuration, e.g. ethos-u55-128.
-        system_config: System configuration to select from the Vela configuration file.
-        memory_mode: Memory mode to select from the Vela configuration file.
-        extra_flags: Extra flags for the Vela compiler.
-        config_ini: Vela configuration file(s) in Python ConfigParser .ini file format.
-    """
+    """Compile specification for Ethos-U NPU targets."""
 
     _TARGET_KEY = "target"
 
@@ -36,6 +27,21 @@ def __init__(
         extra_flags: list[str] | None = None,
         config_ini: str | None = "Arm/vela.ini",
     ):
+        """Normalise Ethos-U compile configuration and compiler flags.
+
+        Args:
+            target (str): Ethos-U accelerator configuration (for example,
+                ``"ethos-u55-128"``).
+            system_config (str | None): System configuration name from the Vela
+                config file. Defaults based on ``target`` when omitted.
+            memory_mode (str | None): Memory mode selection from the Vela config
+                file. Defaults based on ``target`` when omitted.
+            extra_flags (list[str] | None): Additional command-line flags for
+                Vela.
+            config_ini (str | None): Path to a Vela .ini configuration file.
+                Defaults to ``"Arm/vela.ini"``.
+
+        """
         self.target = target
 
         # Set vela compiler flags
@@ -78,16 +84,18 @@ def __init__(
         self.validate()
 
     def to_list(self):
+        """Return compile specs including the encoded Ethos-U target."""
         compile_specs = super().to_list()
         compile_specs.append(CompileSpec(self._TARGET_KEY, self.target.encode()))
         return compile_specs
 
     @classmethod
     def from_list_hook(cls, compile_spec, specs: dict[str, str]):
+        """Restore target-specific metadata from serialized compile specs."""
         compile_spec.target = specs.get(cls._TARGET_KEY, None)
 
     def validate(self):
-        """Throws an error if the compile spec is not valid."""
+        """Validate the configuration against supported Ethos-U settings."""
         if len(self.compiler_flags) == 0:
             raise ValueError(
                 "compile_flags are required in the CompileSpec list for EthosUBackend"
@@ -99,4 +107,5 @@ def validate(self):
 
     @classmethod
     def get_output_format(cls) -> str:
+        """Return the artifact format emitted by this compile spec."""
         return "vela"

backends/arm/tosa/compile_spec.py

@@ -8,12 +8,22 @@
 
 
 class TosaCompileSpec(ArmCompileSpec):
+    """Arm-specific compile spec capturing TOSA serializer requirements."""
+
     def __init__(self, tosa_spec: TosaSpecification | str):
+        """Normalize and store the provided TOSA specification.
+
+        Args:
+            tosa_spec (TosaSpecification | str): Target spec object or version
+                string supported by :meth:`TosaSpecification.create_from_string`.
+
+        """
         if isinstance(tosa_spec, str):
             tosa_spec = TosaSpecification.create_from_string(tosa_spec)
         self._set_compile_specs(tosa_spec, [])
 
     def validate(self):
+        """Ensure that no unsupported compiler flags were supplied."""
         if len(self.compiler_flags) != 0:
             raise ValueError(
                 f"TosaCompileSpec can't have compiler flags, got {self.compiler_flags}"
@@ -22,4 +32,5 @@ def validate(self):
 
     @classmethod
     def get_output_format(cls) -> str:
+        """Return the artifact format emitted by this compile spec."""
         return "tosa"

backends/arm/vgf/compile_spec.py

@@ -15,19 +15,23 @@
 
 
 class VgfCompileSpec(ArmCompileSpec):
-    """
-    Compile spec for VGF compatible targets.
-
-    Args:
-        tosa_spec: TOSA specification that should be targeted.
-        compiler_flags: Extra compiler flags for converter_backend.
-    """
+    """Compile specification for VGF-compatible targets."""
 
     def __init__(
         self,
         tosa_spec: TosaSpecification | str | None = None,
         compiler_flags: list[str] | None = None,
     ):
+        """Normalise inputs and populate the underlying Arm compile spec.
+
+        Args:
+            tosa_spec (TosaSpecification | str | None): TOSA specification to
+                target. Strings are parsed via
+                :meth:`TosaSpecification.create_from_string`. Defaults to
+                ``"TOSA-1.0+FP"``.
+            compiler_flags (list[str] | None): Optional converter-backend flags.
+
+        """
         if tosa_spec is None:
             tosa_spec = "TOSA-1.0+FP"
         if isinstance(tosa_spec, str):
@@ -39,7 +43,7 @@ def __init__(
         self.validate()
 
     def validate(self):
-        """Throws an error if the compile spec is not valid."""
+        """Validate the configuration against VGF-supported TOSA profiles."""
         tosa_version = self.tosa_spec.version  # type: ignore[attr-defined]
         tosa_profiles = self.tosa_spec.profiles  # type: ignore[attr-defined]
 
@@ -63,4 +67,5 @@ def validate(self):
 
     @classmethod
     def get_output_format(cls) -> str:
+        """Return the artifact format emitted by this compile spec."""
         return "vgf"