Per http://microchipdeveloper.com/usb:reset-suspend-resume, which
references the USB specification, a host can issue a device a reset
command by holding both D- and D+ low for 10ms. The specification for
the DFU protocol mentions (Section 2, Overview, steps 2 and 4:
(http://www.usb.org/developers/docs/devclass_docs/DFU_1.1.pdf) that
the USB host issues a USB reset to the device to trigger
reenumeration.
However per a past thread about USB DFU and device resets
(https://www.osronline.com/showthread.cfm?link=252223) seems to imply
that Windows does not expose this functionality for some reason. Per
the documentation for IOCTL_USB_HUB_CYCLE_PORT it was unavailable in
some versions of Windows.
It is my understanding these versions of Windows are thus noncompliant
with the USB specification. Further, it is not very clear to me if any
IOCTLs actually generate the condition described by the standard or a
condition that provokes reenumeration as is intended by the DFU
specification. There is no clear distinction about what is being reset
for some USB IOCTLs. Some do specifically mention they only reset
internal structures.
Can anyone provide some clarification? I have filed a documentation
bug at https://github.com/MicrosoftDocs/windows-driver-docs-ddi/issues/97
but this may be a more serious issue.
Cheers,
R0b0t1