driver-core: add test module for asynchronous probing

This test module tries to test asynchronous driver probing by having a
driver that sleeps for an extended period of time (5 secs) in its
probe() method. It measures the time needed to register this driver
(with device already registered) and a new device (with driver already
registered). The module will fail to load if the time spent in register
call is more than half the probing sleep time.

As a sanity check the driver will then try to synchronously register
driver and device and fail if registration takes less than half of the
probing sleep time.

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/Makefile

@@ -24,5 +24,7 @@ obj-$(CONFIG_PINCTRL) += pinctrl.o
 obj-$(CONFIG_DEV_COREDUMP) += devcoredump.o
 obj-$(CONFIG_GENERIC_MSI_IRQ_DOMAIN) += platform-msi.o
 
+obj-y			+= test/
+
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG