[PATCH 2/6] driver: make struct bus_type::probe optional

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Newly introduce soc_bus_type doesn't define .probe, which would crash
once a driver is registered on that bus. Do as Linux does and defer
to the driver probe function if there's no bus probe function and
treat non-existence of either as a successful probe.

This has the added benefit that it will allow us to drop very simple bus
probe functions that just call the driver probe and do nothing else.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/base/driver.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index babc08f8b6b2..b2d428b70550 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -137,7 +137,12 @@ int device_probe(struct device *dev)
 
 	list_add(&dev->active, &active_device_list);
 
-	ret = dev->bus->probe(dev);
+	if (dev->bus->probe)
+		ret = dev->bus->probe(dev);
+	else if (dev->driver->probe)
+		ret = dev->driver->probe(dev);
+	else
+		ret = 0;
 
 	depth--;
 
-- 
2.39.2