Man page 9 : usb_hcd_check_unlink_urb

usb_hcd_check_unlink_urb - check whether an URB may be unlinked

int usb_hcd_check_unlink_urb(struct usb_hcd *  hcd , struct urb *  urb , int  status );

hcd
    host controller to which urb was submitted

urb
    URB being checked for unlinkability

status
    error code to store in urb if the unlink succeeds

Host controller drivers should call this routine in their dequeue method. The HCDAqs private spinlock must be held and interrupts must be disabled. The actions carried out here are required for making sure than an unlink is valid.

Returns 0 for no error, otherwise a negative error code (in which case the dequeue method must fail). The possible error codes are:

-EIDRM: urb was not submitted or has already completed. The completion function may not have been called yet.

-EBUSY: urb has already been unlinked.