How do I reset USB devices using the Windows API?

Question

Do you know a way to use the Windows XP API to reset the USB bus? In other words, I'd like the OS to kick out any USB devices that are currently connected, and then auto-detect everything anew.

I'm aware of devcon, and I suppose I could do system calls out to it, but I'm hoping for a direct call into the API.

Answer 1

Well, use can use the Setup API (SetupDiXXX functions) to enumerate the USB devices in the system, and then call WinUsb_ResetPipe on each one, but I'm not sure if that's what you're looking for. It's been a while since I worked with USB devices, but as I recall, there is no standard way to reset a device (i.e. simulate a power off/power on cycle). If it's possible for a particular device, you'd have to send an appropriate IOCTL (using DeviceIOControl) to the driver. The IOCTL would vary from manufacturer to manufacturer.

Answer 2

As far as I know, there is no way to do this - you can issue a command to have PnP rescan the bus for new devices, but that isn't the same as issuing a bus reset.

Furthermore, just because from a hardware perspective you issued a bus reset doesn't mean that Windows will remove the PDOs that represent the children of the hub and redetect them; the USB bus driver can (and does) do just what I describe (i.e. issue hardware bus resets without disturbing the device tree), and only after the device doesn't respond does it issue the surprise removal and yank it from the tree.

Answer 3

From kernel mode: You can force a specific USB device to be re-connected, as if it was unplugged and replugged again, by sending an IOCTL_INTERNAL_USB_CYCLE_PORT to its PDO. (This can only be done from a kernel mode, e.g. through a helper driver.) This 'cycle' operation will cause a USB reset to occur, after which the device would be re-enumerated. For example, if the device comes back with a different USB device descriptor, a different driver may be matched for it.

From user mode: You can do this by ejecting the device through the CfgMgr API. For example, to go over all USB hubs and eject all devices:

1. Find all devices having device interface GUID_DEVINTERFACE_USB_HUB with SetupDiGetClassDevs(... DIGCF_DEVICEINTERFACE).
2. Enumerate over the returned device information set (SetupDiEnumDeviceInfo).
3. For each device, get the DevInst member:
   1. Invoke CM_Get_Child(DevInst) and then CM_Get_Sibling repeatedly to go over all child nodes of the hub (i.e. the USB devices).
   2. For each child node, call CM_Request_Device_Eject.