Unable to retrieve bus_type for some devices on Windows

[AlexGuo1998]

On windows, we currently inspect the parent devnode to get bus_type:

hidapi/windows/hid.c

Lines 498 to 552 in 4ebce6b

	/* Get devnode parent */
	cr = CM_Get_Parent(&dev_node, dev_node, 0);
	if (cr != CR_SUCCESS)
	goto end;
	/* Get the compatible ids from parent devnode */
	compatible_ids = hid_internal_get_devnode_property(dev_node, &DEVPKEY_Device_CompatibleIds, DEVPROP_TYPE_STRING_LIST);
	if (!compatible_ids)
	goto end;
	/* Now we can parse parent's compatible IDs to find out the device bus type */
	for (wchar_t* compatible_id = compatible_ids; *compatible_id; compatible_id += wcslen(compatible_id) + 1) {
	/* Normalize to upper case */
	for (wchar_t* p = compatible_id; *p; ++p) *p = towupper(*p);
	/* USB devices
	https://docs.microsoft.com/windows-hardware/drivers/hid/plug-and-play-support
	https://docs.microsoft.com/windows-hardware/drivers/install/standard-usb-identifiers */
	if (wcsstr(compatible_id, L"USB") != NULL) {
	dev->bus_type = HID_API_BUS_USB;
	break;
	}
	/* Bluetooth devices
	https://docs.microsoft.com/windows-hardware/drivers/bluetooth/installing-a-bluetooth-device */
	if (wcsstr(compatible_id, L"BTHENUM") != NULL) {
	dev->bus_type = HID_API_BUS_BLUETOOTH;
	break;
	}
	/* Bluetooth LE devices */
	if (wcsstr(compatible_id, L"BTHLEDEVICE") != NULL) {
	/* HidD_GetProductString/HidD_GetManufacturerString/HidD_GetSerialNumberString is not working for BLE HID devices
	Request this info via dev node properties instead.
	https://docs.microsoft.com/answers/questions/401236/hidd-getproductstring-with-ble-hid-device.html */
	hid_internal_get_ble_info(dev, dev_node);
	dev->bus_type = HID_API_BUS_BLUETOOTH;
	break;
	}
	/* I2C devices
	https://docs.microsoft.com/windows-hardware/drivers/hid/plug-and-play-support-and-power-management */
	if (wcsstr(compatible_id, L"PNP0C50") != NULL) {
	dev->bus_type = HID_API_BUS_I2C;
	break;
	}
	/* SPI devices
	https://docs.microsoft.com/windows-hardware/drivers/hid/plug-and-play-for-spi */
	if (wcsstr(compatible_id, L"PNP0C51") != NULL) {
	dev->bus_type = HID_API_BUS_SPI;
	break;
	}
	}

However, some filtered HID device (e.g. imbushuo/mac-precision-touchpad) whose parent is the filter driver, which don't have a correct compatible_id. The device tree is like this:

...                                           (page usage)
Microsoft Bluetooth Enumerator
|- Bluetooth HID device                                   <- 3
   |- Apple Multi-touch Auxiliary Services    (FF00 0014)
   |- Apple Multi-touch Trackpad HID Filter               <- 2
      |- Microsoft Input Configuration Device (000D 000E)
      |- HID Compactible Trackpad             (000D 0005) <- 1

If we want to know the bus_type for (1), according to the code, we're inspecting the compatible_id for (2), which is empty.

However if we go one step further we hit (3), which has the correct compatible_id: BTHENUM\{GUID}. Now we know it's a Bluetooth device.

---

I suggest we go all the way up, until to the root to find a recognizable compatible_id, and stop after we found one.

I don't really know if this is the correct / sane thing to do. Could you give me some ideas?

---

BTW, on a UEFI laptop some devices have a ancestor with a compatible_id like *PNP0A03, but no more recognizable value. Do you know what that is? (Maybe we can open another issue for this?)

[Youw]

is #464 of any relevance to the issue described here?

[AlexGuo1998]

I'm not quite sure but maybe no.

In this situation, we don't even find USB in any of the compatible_ids, while #464 attempts to add some extra logic in if(wcsstr(compatible_id, L"USB") != NULL)

[JoergAtGithub]

@DJm00n can you help with this Bluetooth bus_type issue?

[Youw]

I suggest we go all the way up, until to the root to find a recognizable compatible_id, and stop after we found one.

This does sounds like a good solution. But I guess i has to be in line with other changes (including #464).

[DJm00n]

@AlexGuo1998 thank you for reporting. I'll review cr = CM_Get_Parent(&dev_node, dev_node, 0); after #464 get merged.

PS: according to the C:\Windows\INF\pci.inf PNP0A03 is a "PCI Bus".

[mcuee]

@DJm00n

#464 has been merged. Maybe you want to take a look at this issue now.