Try to fetch events from nlsysevent or devd to determine when
to scan the usb bus for devices addition or removal.
if none are available fallback on the regular timer based (4s)
scanner
if devd socket or netlink socket is closed or error fallback on the
timer based method.
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D48300
When a hotplug callback has been registered, and the program using
libusb is calling libusb_exit then the thread handler is set to
NO_THREAD which result in the variable controlling the loop the be set
to 0, it does a last pass through device available without having done
a scan, which result in a sigbus after it tried to unregister all the
devices.
directly break the loop instead and cleanup the list of devices
this fixes the tests with LGPLed libusb's hotplugtest program
MFC After: 3 days
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D48298
devices are enumerated regardless of of the LIBUSB_HOTPLUG_ENUMERATE
flag. Make sure when the flag is not specified no arrival events are
generated for currently enumerated devices.
MFC after: 3 days
Sponsored by: Mellanox Technologies
libusb_hotplug_deregister_callback() for the LibUSB v1.0 API and
update the libusb(3) manual page.
Approved by: re (kib)
Requested by: swills
MFC after: 1 week
