Scsi - Index of

759 * Completion Callbacks:
760 *
761 * The completion callback is made in_interrupt(), and one of the first
762 * things that a completion handler should do is check the status field.
763 * The status field is provided for all URBs. It is used to report
764 * unlinked URBs, and status for all non-ISO transfers. It should not
765 * be examined before the URB is returned to the completion handler.
766 *
767 * The context field is normally used to link URBs back to the relevant
768 * driver or request state.
769 *
770 * When the completion callback is invoked for non-isochronous URBs, the
771 * actual_length field tells how many bytes were transferred. This field
772 * is updated even when the URB terminated with an error or was unlinked.
773 *
774 * ISO transfer status is reported in the status and actual_length fields
775 * of the iso_frame_desc array, and the number of errors is reported in
776 * error_count. Completion callbacks for ISO transfers will normally
777 * (re)submit URBs to ensure a constant transfer rate.
778 */
779 struct urb
780 {
781 /* private, usb core and host controller only fields in the urb */
782 struct kref kref; /* reference count of the URB */
783 spinlock_t lock; /* lock for the URB */
784 void *hcpriv; /* private data for host controller */
785 struct list_head urb_list; /* list pointer to all active urbs */
786 int bandwidth; /* bandwidth for INT/ISO request */
787 atomic_t use_count; /* concurrent submissions counter */
788 u8 reject; /* submissions will fail */
789
68
790 /* public, documented fields in the urb that can be used by drivers */
791 struct usb_device *dev; /* (in) pointer to associated device */
792 unsigned int pipe; /* (in) pipe information */
793 int status; /* (return) non-ISO status */
794 unsigned int transfer_flags; /* (in) URB_SHORT_NOT_OK | ...*/
795 void *transfer_buffer; /* (in) associated data buffer */
796 dma_addr_t transfer_dma; /* (in) dma addr for transfer_buffer */
797 int transfer_buffer_length; /* (in) data buffer length */
798 int actual_length; /* (return) actual transfer length */
799 unsigned char *setup_packet; /* (in) setup packet (control only) */
800 dma_addr_t setup_dma; /* (in) dma addr for setup_packet */
801 int start_frame; /* (modify) start frame (ISO) */