On Thu, Apr 08, 2021 at 10:36:11PM +0200, Hans de Goede wrote: > usb_role_switch_find_by_fwnode() returns a reference to the role-switch > which must be put by calling usb_role_switch_put(). > > usb_role_switch_put() calls module_put(sw->dev.parent->driver->owner), > add a matching try_module_get() to usb_role_switch_find_by_fwnode(), > making it behave the same as the other usb_role_switch functions > which return a reference. > > This avoids a WARN_ON being hit at kernel/module.c:1158 due to the > module-refcount going below 0. > Took me a while to figure out what the subject line is supposed to mean. s/Cakk/Call/ Otherwise Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx> It might be useful though to explain the difference between fwnode_usb_role_switch_get() and usb_role_switch_find_by_fwnode(), and why two different functions are needed, both passing fwnode as parameter and returning a pointer to usb_role_switch. Thanks, Guenter > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > drivers/usb/roles/class.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c > index 97f37077b7f9..33b637d0d8d9 100644 > --- a/drivers/usb/roles/class.c > +++ b/drivers/usb/roles/class.c > @@ -189,6 +189,8 @@ usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode) > return NULL; > > dev = class_find_device_by_fwnode(role_class, fwnode); > + if (dev) > + WARN_ON(!try_module_get(dev->parent->driver->owner)); > > return dev ? to_role_switch(dev) : NULL; > } > -- > 2.30.2 >
