Commit 27ef1784 authored by Vincent Mailhol's avatar Vincent Mailhol Committed by Greg Kroah-Hartman
Browse files

usb: add usb_set_intfdata() documentation 

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: default avatarVincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/r/20221128102954.3615579-1-mailhol.vincent@wanadoo.fr


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 01792c60

drivers/usb/usb-skeleton.c

+0 −1
Original line number Diff line number Diff line
@@ -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);

include/linux/usb.h

+12 −0
Original line number Diff line number Diff line
@@ -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);