Expose System sub-resources based on driver support

Only advertise BIOS, Processors, and SimpleStorage when the driver
supports them, preventing non-functional endpoints.

Driver support matrix:

| Driver    | BIOS | Processors | SimpleStorage |
|-----------|------|------------|---------------|
| libvirt   | ✓    | ✓          | ✓             |
| nova      | ✗    | ✗          | ✗             |
| ironic    | ✗    | ✗          | ✗             |
| fake      | ✗    | ✗          | ✗             |

Assisted-By: Claude Code/claude-4.5-sonnet
Change-Id: I12da36642a92ff6e66c23987c2a7d0f002f0f435
Signed-off-by: Harald Jensås <hjensas@redhat.com>

releasenotes/notes/expose-system-sub-resources-based-on-driver-support-57f467d2b5c62bc6.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    System sub-resources (``BIOS``, ``Processors``, and ``SimpleStorage``) are
+    now conditionally exposed based on driver support. Only the libvirt driver
+    implements these features, so they will only appear in the System resource
+    response when using the libvirt backend. This prevents exposing non-
+    functional endpoints for drivers that don't support these capabilities.
+    When these fields are absent, Redfish clients like Ironic will receive a
+    ``MissingAttributeError`` and handle it gracefully.

sushy_tools/emulator/main.py

@@ -468,6 +468,10 @@ def system_resource(identity):
             power_state=app.systems.get_power_state(identity),
             total_memory_gb=try_get(app.systems.get_total_memory),
             bios_version=bios_version,
+            bios_supported=try_get(app.systems.get_bios),
+            processors_supported=try_get(app.systems.get_processors),
+            simple_storage_supported=try_get(
+                app.systems.get_simple_storage_collection),
             total_cpus=try_get(app.systems.get_total_cpus),
             boot_source_target=app.systems.get_boot_device(identity),
             boot_source_mode=try_get(app.systems.get_boot_mode),

sushy_tools/emulator/templates/system.json

@@ -63,22 +63,30 @@
             "HealthRollUp": "OK"
         }
     },
+    {%- if bios_supported %}
     "Bios": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/BIOS"|format(identity)|tojson }}
     },
+    {%- endif %}
+    {%- if bios_version %}
     "BiosVersion": {{ bios_version|string|tojson  }},
+    {%- endif %}
+    {%- if processors_supported %}
     "Processors": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/Processors"|format(identity)|tojson }}
     },
+    {%- endif %}
     "Memory": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/Memory"|format(identity)|tojson }}
     },
     "SecureBoot": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/SecureBoot"|format(identity)|tojson }}
     },
+    {%- if simple_storage_supported %}
     "SimpleStorage": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/SimpleStorage"|format(identity)|tojson }}
     },
+    {%- endif %}
     "Storage": {
         "@odata.id": {{ "/redfish/v1/Systems/%s/Storage"|format(identity)|tojson }}
     },

sushy_tools/tests/unit/emulator/test_main.py

@@ -573,6 +573,191 @@ class BiosTestCase(EmulatorTestCase):
         systems_mock.return_value.reset_bios.assert_called_once_with(self.uuid)
 
 
+class ConditionalResourceAdvertisingTestCase(EmulatorTestCase):
+    """Test that resources are only advertised when driver supports them"""
+
+    def setUp(self):
+        super(ConditionalResourceAdvertisingTestCase, self).setUp()
+        self.set_feature_set("full")
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_bios_advertised_when_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test BIOS is advertised when driver supports it"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_bios.return_value = {'attr1': 'value1'}
+        systems_mock.get_processors.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.side_effect = (
+            error.NotSupportedError)
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertIn('Bios', response.json)
+        self.assertEqual(
+            '/redfish/v1/Systems/xxxx-yyyy-zzzz/BIOS',
+            response.json['Bios']['@odata.id'])
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_bios_not_advertised_when_not_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test BIOS is NOT advertised when driver doesn't support it"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_bios.side_effect = error.NotSupportedError
+        systems_mock.get_processors.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.side_effect = (
+            error.NotSupportedError)
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertNotIn('Bios', response.json)
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_processors_advertised_when_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test Processors is advertised when driver supports it"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_processors.return_value = [{'id': 'CPU'}]
+        systems_mock.get_bios.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.side_effect = (
+            error.NotSupportedError)
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertIn('Processors', response.json)
+        self.assertEqual(
+            '/redfish/v1/Systems/xxxx-yyyy-zzzz/Processors',
+            response.json['Processors']['@odata.id'])
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_processors_not_advertised_when_not_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test Processors is NOT advertised when driver doesn't support it"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_processors.side_effect = error.NotSupportedError
+        systems_mock.get_bios.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.side_effect = (
+            error.NotSupportedError)
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertNotIn('Processors', response.json)
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_simple_storage_advertised_when_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test SimpleStorage is advertised when driver supports it"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.return_value = (
+            {'virtio': {}})
+        systems_mock.get_bios.side_effect = error.NotSupportedError
+        systems_mock.get_processors.side_effect = error.NotSupportedError
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertIn('SimpleStorage', response.json)
+        self.assertEqual(
+            '/redfish/v1/Systems/xxxx-yyyy-zzzz/SimpleStorage',
+            response.json['SimpleStorage']['@odata.id'])
+
+    @patch_resource('indicators')
+    @patch_resource('chassis')
+    @patch_resource('managers')
+    @patch_resource('systems')
+    def test_simple_storage_not_advertised_when_not_supported(
+            self, systems_mock, managers_mock, chassis_mock, indicators_mock):
+        """Test SimpleStorage NOT advertised when driver doesn't support"""
+        systems_mock = systems_mock.return_value
+        systems_mock.uuid.return_value = 'zzzz-yyyy-xxxx'
+        systems_mock.get_power_state.return_value = 'On'
+        systems_mock.get_boot_device.return_value = 'Cd'
+        systems_mock.get_boot_mode.side_effect = error.NotSupportedError
+        systems_mock.get_simple_storage_collection.side_effect = (
+            error.NotSupportedError)
+        systems_mock.get_bios.side_effect = error.NotSupportedError
+        systems_mock.get_processors.side_effect = error.NotSupportedError
+        systems_mock.get_total_memory.side_effect = error.NotSupportedError
+        systems_mock.get_total_cpus.side_effect = error.NotSupportedError
+        systems_mock.get_versions.side_effect = error.NotSupportedError
+        managers_mock.return_value.get_managers_for_system.return_value = []
+        chassis_mock.return_value.chassis = []
+        indicators_mock.return_value.get_indicator_state.return_value = 'Off'
+
+        response = self.app.get('/redfish/v1/Systems/xxxx-yyyy-zzzz')
+
+        self.assertEqual(200, response.status_code)
+        self.assertNotIn('SimpleStorage', response.json)
+
+
 @patch_resource('systems')
 class EthernetInterfacesTestCase(EmulatorTestCase):