hwmon: identify hidraw devices with a matching hwmon device

For now only HIDRAW is supported: this means that only HIDs are
supported, and hidapi must have been compiled with support for HIDRAW.

Related: #403

liquidctl/driver/hwmon.py

@@ -0,0 +1,53 @@
+# uses the psf/black style
+
+import logging
+import sys
+from pathlib import Path
+
+_LOGGER = logging.getLogger(__name__)
+_IS_LINUX = sys.platform == "linux"
+
+
+class HwmonDevice:
+    """Unstable API."""
+
+    __slots__ = [
+        "module",
+        "path",
+    ]
+
+    def __init__(self, module, path):
+        self.module = module
+        self.path = path
+
+    @property
+    def name(self):
+        return self.path.name
+
+    @classmethod
+    def from_hidraw(cls, path):
+        """Find the `HwmonDevice` for `path`."""
+
+        if not _IS_LINUX:
+            return None
+
+        if not path.startswith(b"/dev/hidraw"):
+            _LOGGER.debug("cannot search hwmon device for %s: unsupported path", path)
+            return None
+
+        path = path.decode()
+        name = path[5:]
+        class_path = Path("/sys/class/hidraw", name)
+
+        sys_device = class_path / "device"
+        hwmon_devices = (sys_device / "hwmon").iterdir()
+
+        hwmon_path = next(hwmon_devices)
+
+        if next(hwmon_devices, None) is not None:
+            _LOGGER.debug("cannot pick hwmon device for %s: more than one alternative", path)
+            return None
+
+        module = (sys_device / "driver" / "module").readlink().name
+
+        return HwmonDevice(module, hwmon_path)

liquidctl/driver/usb.py

@@ -68,6 +68,7 @@ except ModuleNotFoundError:
     import hid
 
 from liquidctl.driver.base import BaseDriver, BaseBus, find_all_subclasses
+from liquidctl.driver.hwmon import HwmonDevice
 from liquidctl.util import LazyHexRepr
 
 _LOGGER = logging.getLogger(__name__)
@@ -196,6 +197,10 @@ class UsbHidDriver(BaseUsbDriver):
             assert hidinfo, 'Could not find device in HID bus'
             device = HidapiDevice(hid, hidinfo)
         super().__init__(device, description, **kwargs)
+        self._hwmon = HwmonDevice.from_hidraw(device.path)
+        if self._hwmon:
+            _LOGGER.debug('HID is bound to %s kernel driver: %s', self._hwmon.module,
+                          self._hwmon.path)
 
 
 class UsbDriver(BaseUsbDriver):
@@ -482,6 +487,10 @@ class HidapiDevice:
         for info in infos:
             yield cls(api, info)
 
+    @property
+    def path(self):
+        return self.hidinfo['path']
+
     @property
     def vendor_id(self):
         return self.hidinfo['vendor_id']

tests/_testutils.py

@@ -24,13 +24,14 @@ class MockRuntimeStorage(RuntimeStorage):
 
 class MockHidapiDevice:
     def __init__(self, vendor_id=None, product_id=None, release_number=None,
-                 serial_number=None, bus=None, address=None):
+                 serial_number=None, bus=None, address=None, path=None):
         self.vendor_id = vendor_id
         self.product_id = product_id
         self.release_number = release_number
         self.serial_number = serial_number
         self.bus = bus
         self.address = address
+        self.path = path or b'<placeholder path>'
         self.port = None
 
         self.open = noop

tests/test_backward_compatibility_11.py

@@ -23,14 +23,14 @@ class _MockPyUsbHandle(usb.core.Device):
 
 def _mock_enumerate(vendor_id=0, product_id=0):
     return [
-        {'vendor_id': vendor_id, 'product_id': product_id, 'serial_number': '987654321'},
-        {'vendor_id': vendor_id, 'product_id': product_id, 'serial_number': '123456789'}
+        {'vendor_id': vendor_id, 'product_id': product_id, 'serial_number': '_21', 'path': b'/_21'},
+        {'vendor_id': vendor_id, 'product_id': product_id, 'serial_number': '_89', 'path': b'/_89'}
     ]
 
 
 def test_construct_with_raw_pyusb_handle(monkeypatch):
     monkeypatch.setattr(hid, 'enumerate', _mock_enumerate)
-    pyusb_handle = _MockPyUsbHandle(serial_number='123456789')
+    pyusb_handle = _MockPyUsbHandle(serial_number='_89')
     liquidctl_device = Kraken2(pyusb_handle, 'Some device')
     assert liquidctl_device.device.vendor_id == pyusb_handle.idVendor, \
         '<driver instance>.device points to incorrect physical device'

tests/test_commander_core.py

@@ -16,6 +16,7 @@ class MockCommanderCoreDevice:
         self.vendor_id = 0x1b1c
         self.product_id = 0x0c1c
         self.address = 'addr'
+        self.path = b'path'
         self.release_number = None
         self.serial_number = None
         self.bus = None

tests/test_hwmon.py

@@ -0,0 +1,27 @@
+# uses the psf/black style
+
+import pytest
+
+from liquidctl.driver.hwmon import HwmonDevice
+
+
+@pytest.fixture
+def mock_hwmon(tmp_path):
+    hwmon = tmp_path / "hwmon7"
+    hwmon.mkdir()
+
+    (hwmon / "fan1_input").write_text("1499\n")
+
+    return HwmonDevice("mock_module", hwmon)
+
+
+def test_has_module(mock_hwmon):
+    assert mock_hwmon.module == "mock_module"
+
+
+def test_has_path(mock_hwmon):
+    assert mock_hwmon.path.is_dir()
+
+
+def test_has_name(mock_hwmon):
+    assert mock_hwmon.name == "hwmon7"