USB: Add support for SuperSpeed isoc endpoints

Use the Mult and bMaxBurst values from the endpoint companion
descriptor to calculate the max length of an isoc transfer.

Add USB_SS_MULT macro to access Mult field of bmAttributes, at
Sarah's suggestion.

This patch should be queued for the 2.6.36 and 2.6.37 stable trees, since
those were the first kernels to have isochronous support for SuperSpeed
devices.
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org

drivers/usb/core/urb.c

@@ -366,7 +366,16 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 	if (xfertype == USB_ENDPOINT_XFER_ISOC) {
 		int	n, len;
 
-		/* FIXME SuperSpeed isoc endpoints have up to 16 bursts */
+		/* SuperSpeed isoc endpoints have up to 16 bursts of up to
+		 * 3 packets each
+		 */
+		if (dev->speed == USB_SPEED_SUPER) {
+			int     burst = 1 + ep->ss_ep_comp.bMaxBurst;
+			int     mult = USB_SS_MULT(ep->ss_ep_comp.bmAttributes);
+			max *= burst;
+			max *= mult;
+		}
+
 		/* "high bandwidth" mode, 1-3 packets/uframe? */
 		if (dev->speed == USB_SPEED_HIGH) {
 			int	mult = 1 + ((max >> 11) & 0x03);

include/linux/usb/ch9.h

@@ -585,6 +585,8 @@ struct usb_ss_ep_comp_descriptor {
 #define USB_DT_SS_EP_COMP_SIZE		6
 /* Bits 4:0 of bmAttributes if this is a bulk endpoint */
 #define USB_SS_MAX_STREAMS(p)		(1 << ((p) & 0x1f))
+/* Bits 1:0 of bmAttributes if this is an isoc endpoint */
+#define USB_SS_MULT(p)			(1 + ((p) & 0x3))
 
 /*-------------------------------------------------------------------------*/