USB drivers do not need to call usb_set_intfdata(intf, NULL) in their usb_driver::disconnect callback because the core already does it in [1]. However, this fact is widely unknown, c.f.: $ git grep "usb_set_intfdata(.*NULL)" | wc -l 215 Especially, setting the interface to NULL before all action completed can result in a NULL pointer dereference. Not calling usb_set_intfdata() at all in disconnect() is the safest method. Add documentation to usb_set_intfdata() to clarify this point. Also remove the call in usb-skeletion's disconnect() not to confuse the new comers. [1] function usb_unbind_interface() from drivers/usb/core/driver.c Link: https://elixir.bootlin.com/linux/v6.0/source/drivers/usb/core/driver.c#L497 Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> --- drivers/usb/usb-skeleton.c | 1 - include/linux/usb.h | 12 ++++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c index d87deee3e26e..900a64ad25e4 100644 --- a/drivers/usb/usb-skeleton.c +++ b/drivers/usb/usb-skeleton.c @@ -564,7 +564,6 @@ static void skel_disconnect(struct usb_interface *interface) int minor = interface->minor; dev = usb_get_intfdata(interface); - usb_set_intfdata(interface, NULL); /* give back our minor */ usb_deregister_dev(interface, &skel_class); diff --git a/include/linux/usb.h b/include/linux/usb.h index 9ff1ad4dfad1..d4afeeec1e1a 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -265,6 +265,18 @@ static inline void *usb_get_intfdata(struct usb_interface *intf) return dev_get_drvdata(&intf->dev); } +/** + * usb_set_intfdata() - associate driver-specific data with the interface + * @intf: the usb interface + * @data: pointer to the device priv structure or %NULL + * + * Drivers should use this function in their probe() to associate their + * driver-specific data with the usb interface. + * + * When disconnecting, the core will take care of setting @intf back to %NULL, + * so no actions are needed on the driver side. The interface should not be set + * to %NULL before all actions completed (e.g. no outsanding URB remaining). + */ static inline void usb_set_intfdata(struct usb_interface *intf, void *data) { dev_set_drvdata(&intf->dev, data); -- 2.25.1
