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

[Sasha Levin]

ULPI registers it's 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-existant 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@xxxxxxxxxx>
---
 drivers/usb/common/ulpi.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
index 0e6f968..0b0a5e7 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 (!ulpi_bus.p)
+		return -ENODEV;
+
 	drv->driver.bus = &ulpi_bus;
 
 	return driver_register(&drv->driver);
-- 
1.7.10.4

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