If suspend callback fails in system sleep context, usb core will
ignore the failure and let system sleep go ahead further, so
this patch comments on the case and requires that both
usbnet_suspend() and subdriver->suspend() MUST return 0 in
system sleep context.
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NBjørn Mork <bjorn@mork.no>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>