diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/usb.h | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/include/linux/usb.h b/include/linux/usb.h index 7a62399fd5e8..8e8f953ed2c7 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -767,7 +767,6 @@ typedef void (*usb_complete_t)(struct urb *); /** * struct urb - USB Request Block * @urb_list: For use by current owner of the URB. - * @next: Used to link ISO requests into rings. * @pipe: Holds endpoint number, direction, type, and max packet size. * Create these values with the eight macros available; * usb_{snd,rcv}TYPEpipe(dev,endpoint), where the type is "ctrl" @@ -827,7 +826,7 @@ typedef void (*usb_complete_t)(struct urb *); * * Initialization: * - * All URBs submitted must initialize dev, pipe, next (may be null), + * All URBs submitted must initialize dev, pipe, * transfer_flags (may be zero), complete, timeout (may be zero). * The USB_ASYNC_UNLINK transfer flag affects later invocations of * the usb_unlink_urb() routine. @@ -873,7 +872,9 @@ typedef void (*usb_complete_t)(struct urb *); * the quality of service is only "best effort". Callers provide specially * allocated URBs, with number_of_packets worth of iso_frame_desc structures * at the end. Each such packet is an individual ISO transfer. Isochronous - * URBs are normally submitted with urb->next fields set up as a ring, so + * URBs are normally queued (no flag like USB_BULK_QUEUE is needed) so that + * transfers are at least double buffered, and then explicitly resubmitted + * in completion handlers, so * that data (such as audio or video) streams at as constant a rate as the * host controller scheduler can support. * @@ -891,14 +892,15 @@ typedef void (*usb_complete_t)(struct urb *); * When completion callback is invoked for non-isochronous URBs, the * actual_length field tells how many bytes were transferred. * - * For interrupt and isochronous URBs, the URB provided to the callback + * For interrupt URBs, the URB provided to the callback * function is still "owned" by the USB core subsystem unless the status * indicates that the URB has been unlinked. Completion handlers should * not modify such URBs until they have been unlinked. * * ISO transfer status is reported in the status and actual_length fields * of the iso_frame_desc array, and the number of errors is reported in - * error_count. + * error_count. Completion callbacks for ISO transfers will normally + * (re)submit URBs to ensure a constant transfer rate. */ struct urb { @@ -906,7 +908,6 @@ struct urb atomic_t count; /* reference count of the URB */ void *hcpriv; /* private data for host controller */ struct list_head urb_list; /* list pointer to all active urbs */ - struct urb *next; /* (in) pointer to next URB */ struct usb_device *dev; /* (in) pointer to associated device */ unsigned int pipe; /* (in) pipe information */ int status; /* (return) non-ISO status */ |