The previous memcpy implementation relied on the size advertized by the
device. There were no guarantees that buf was big enough.
Some gymnastic is also required with the +2/-2 to take into account
the first 2 bytes of the returned buffer where the total returned
length is supplied by the device.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>