firmware: arm_scmi: Ensure drivers provide a probe function

The bus probe callback calls the driver callback without further
checking. Better be safe than sorry and refuse registration of a driver
without a probe function to prevent a NULL pointer exception.

Link: https://lore.kernel.org/r/20210624095059.4010157-2-sudeep.holla@arm.com
Fixes: 933c504424a2 ("firmware: arm_scmi: add scmi protocol bus to enumerate protocol devices")
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index dc113ad..6c7e249 100644 (file)
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -134,6 +134,9 @@ int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
 {
        int retval;
 
+       if (!driver->probe)
+               return -EINVAL;
+
        retval = scmi_protocol_device_request(driver->id_table);
        if (retval)
                return retval;