commit afd700d9 upstream.

The FF2 driver (usbhid/hid-pidff.c) sends commands to the stick during ff_init.
However, this is called inside a block where driver_input_lock is locked, so
the results of these initial commands are discarded. This behavior is the
"killer", without this nothing else works.

ff_init issues commands using "hid_hw_request". This eventually goes to
hid_input_report, which returns -EBUSY because driver_input_lock is locked. The
change is to delay the ff_init call in hid-core.c until after this lock has
been released.

Calling hid_device_io_start() releases the lock so the device can be
configured.  We also need to call hid_device_io_stop() on exit for the lock to
remain locked while ending the init of the drivers.

[ benjamin.tissoires@redhat.com: imrpoved the changelog a lot ]
Signed-off-by: Jim Keir <jimkeir@oracledbadirect.com>
Reviewed-by: Benjamin.tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>