Implementing dynamic device modules

Dynamic modules may be loaded automatically on device initialization if
the device supports them. Dynamic modules implent probe() method to
determine whether they are supported by a particular deviced.

devcpufreq and cpuidle have been converted into dynamic modules

wlauto/common/linux/device.py

@@ -107,6 +107,11 @@ class BaseLinuxDevice(Device):  # pylint: disable=abstract-method
                       value_name='tunables'),
     ]
 
+    dynamic_modules = [
+        'devcpufreq',
+        'cpuidle',
+    ]
+
     @property
     def abi(self):
         if not self._abi:

wlauto/core/device.py

@@ -35,6 +35,7 @@ from collections import OrderedDict
 from contextlib import contextmanager
 
 from wlauto.core.extension import Extension, ExtensionMeta, AttributeCollection, Parameter
+from wlauto.core.extension_loader import ExtensionLoader
 from wlauto.exceptions import DeviceError, ConfigError
 from wlauto.utils.types import list_of_integers, list_of, caseless_string
 
@@ -93,10 +94,34 @@ class CoreParameter(RuntimeParameter):
         return params
 
 
+class DynamicModuleSpec(dict):
+
+    @property
+    def name(self):
+        return self.keys()[0]
+
+    def __init__(self, *args, **kwargs):
+        dict.__init__(self)
+        if args:
+            if len(args) > 1:
+                raise ValueError(args)
+            value = args[0]
+        else:
+            value = kwargs
+        if isinstance(value, basestring):
+            self[value] = {}
+        elif isinstance(value, dict) and len(value) == 1:
+            for k, v in value.iteritems():
+                self[k] = v
+        else:
+            raise ValueError(value)
+
+
 class DeviceMeta(ExtensionMeta):
 
     to_propagate = ExtensionMeta.to_propagate + [
         ('runtime_parameters', RuntimeParameter, AttributeCollection),
+        ('dynamic_modules', DynamicModuleSpec, AttributeCollection),
     ]
 
 
@@ -157,6 +182,9 @@ class Device(Extension):
     ]
 
     runtime_parameters = []
+    # dynamic modules are loaded or not based on whether the device supports
+    # them (established at runtime by module probling the device).
+    dynamic_modules = []
 
     # These must be overwritten by subclasses.
     name = None
@@ -197,7 +225,17 @@ class Device(Extension):
         been connecte).
 
         """
-        pass
+        loader = ExtensionLoader()
+        for module_spec in self.dynamic_modules:
+            module = self._load_module(loader, module_spec)
+            if not hasattr(module, 'probe'):
+                message = 'Module {} does not have "probe" attribute; cannot be loaded dynamically'
+                raise ValueError(message.format(module.name))
+            if module.probe(self):
+                self.logger.debug('Installing module "{}"'.format(module.name))
+                self._install_module(module)
+            else:
+                self.logger.debug('Module "{}" is not supported by the device'.format(module.name))
 
     def reset(self):
         """

wlauto/core/extension.py

@@ -598,28 +598,8 @@ class Extension(object):
         for module_spec in modules:
             if not module_spec:
                 continue
-            if isinstance(module_spec, basestring):
+            module = self._load_module(loader, module_spec)
-                name = module_spec
+            self._install_module(module)
-                params = {}
-            elif isinstance(module_spec, dict):
-                if len(module_spec) != 1:
-                    message = 'Invalid module spec: {}; dict must have exctly one key -- the module name.'
-                    raise ValueError(message.format(module_spec))
-                name, params = module_spec.items()[0]
-            else:
-                message = 'Invalid module spec: {}; must be a string or a one-key dict.'
-                raise ValueError(message.format(module_spec))
-
-            if not isinstance(params, dict):
-                message = 'Invalid module spec: {}; dict value must also be a dict.'
-                raise ValueError(message.format(module_spec))
-
-            module = loader.get_module(name, owner=self, **params)
-            module.initialize(None)
-            for capability in module.capabilities:
-                if capability not in self.capabilities:
-                    self.capabilities.append(capability)
-            self._modules.append(module)
 
     def has(self, capability):
         """Check if this extension has the specified capability. The alternative method ``can`` is
@@ -629,6 +609,33 @@ class Extension(object):
 
     can = has
 
+    def _load_module(self, loader, module_spec):
+        if isinstance(module_spec, basestring):
+            name = module_spec
+            params = {}
+        elif isinstance(module_spec, dict):
+            if len(module_spec) != 1:
+                message = 'Invalid module spec: {}; dict must have exctly one key -- the module name.'
+                raise ValueError(message.format(module_spec))
+            name, params = module_spec.items()[0]
+        else:
+            message = 'Invalid module spec: {}; must be a string or a one-key dict.'
+            raise ValueError(message.format(module_spec))
+
+        if not isinstance(params, dict):
+            message = 'Invalid module spec: {}; dict value must also be a dict.'
+            raise ValueError(message.format(module_spec))
+
+        module = loader.get_module(name, owner=self, **params)
+        module.initialize(None)
+        return module
+
+    def _install_module(self, module):
+        for capability in module.capabilities:
+            if capability not in self.capabilities:
+                self.capabilities.append(capability)
+        self._modules.append(module)
+
     def __check_from_loader(self):
         """
         There are a few things that need to happen in order to get a valide extension instance.

wlauto/modules/cpufreq.py

@@ -28,6 +28,10 @@ class CpufreqModule(Module):
     """
     capabilities = ['cpufreq']
 
+    def probe(self, device):  # pylint: disable=no-self-use
+        path = '/sys/devices/system/cpu/cpufreq'
+        return device.file_exists(path)
+
     def initialize(self, context):
         # pylint: disable=W0201
         CpufreqModule._available_governors = {}

wlauto/modules/cpuidle.py

@@ -86,6 +86,9 @@ class Cpuidle(Module):
 
     root_path = '/sys/devices/system/cpu/cpuidle'
 
+    def probe(self, device):
+        return device.file_exists(self.root_path)
+
     def initialize(self, context):
         self.device = self.root_owner
         signal.connect(self._on_device_init, signal.RUN_INIT, priority=1)