[PATCH 1/1] usb: ulpi: don't register drivers if bus doesn't exist

[Lu Baolu <baolu.lu@linux.intel.com>]

ULPI registers its bus at module_init, so if the bus fails to register, the
module will fail to load and all will be well in the world.

However, if the ULPI code is built-in rather than a module, the bus
initialization may fail, but we'd still try to register drivers later onto
a non-existent bus, which will panic the kernel.

Fix that by checking that the bus was indeed initialized before trying to
register drivers on top of it.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reported-by: Zhuo Qiuxu <qiuxu.zhuo@intel.com>
Reviewed-by: David Cohen <david.a.cohen@linux.intel.com>
---
 drivers/usb/common/ulpi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
index 0e6f968..af52b46 100644
--- a/drivers/usb/common/ulpi.c
+++ b/drivers/usb/common/ulpi.c
@@ -132,6 +132,10 @@ int ulpi_register_driver(struct ulpi_driver *drv)
 	if (!drv->probe)
 		return -EINVAL;
 
+	/* Was the bus registered successfully? */
+	if (unlikely(WARN_ON(!ulpi_bus.p)))
+		return -ENODEV;
+
 	drv->driver.bus = &ulpi_bus;
 
 	return driver_register(&drv->driver);
@@ -242,7 +246,7 @@ static int __init ulpi_init(void)
 {
 	return bus_register(&ulpi_bus);
 }
-module_init(ulpi_init);
+subsys_initcall(ulpi_init);
 
 static void __exit ulpi_exit(void)
 {
-- 
2.1.4