USB: OHCI: add SG support

Apparently nobody ever remembered to add Scatter-Gather support to
ohci-hcd. This patch adds it.

Signed-off-by: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/ohci-hcd.c

···
 
 /*-------------------------------------------------------------------------*/
 
+static int number_of_tds(struct urb *urb)
+{
+	int			len, i, num, this_sg_len;
+	struct scatterlist	*sg;
+
+	len = urb->transfer_buffer_length;
+	i = urb->num_mapped_sgs;
+
+	if (len > 0 && i > 0) {		/* Scatter-gather transfer */
+		num = 0;
+		sg = urb->sg;
+		for (;;) {
+			this_sg_len = min_t(int, sg_dma_len(sg), len);
+			num += DIV_ROUND_UP(this_sg_len, 4096);
+			len -= this_sg_len;
+			if (--i <= 0 || len <= 0)
+				break;
+			sg = sg_next(sg);
+		}
+
+	} else {			/* Non-SG transfer */
+		/* one TD for every 4096 Bytes (could be up to 8K) */
+		num = DIV_ROUND_UP(len, 4096);
+	}
+	return num;
+}
+
 /*
  * queue up an urb for anything except the root hub
  */
···
 		// case PIPE_INTERRUPT:
 		// case PIPE_BULK:
 		default:
-			/* one TD for every 4096 Bytes (can be up to 8K) */
-			size += urb->transfer_buffer_length / 4096;
-			/* ... and for any remaining bytes ... */
-			if ((urb->transfer_buffer_length % 4096) != 0)
-				size++;
-			/* ... and maybe a zero length packet to wrap it up */
+			size += number_of_tds(urb);
+			/* maybe a zero-length packet to wrap it up */
 			if (size == 0)
 				size++;
 			else if ((urb->transfer_flags & URB_ZERO_PACKET) != 0
···
 {
 	int ret;
 	struct usb_hcd *hcd = ohci_to_hcd(ohci);
+
+	/* Accept arbitrarily long scatter-gather lists */
+	hcd->self.sg_tablesize = ~0;
 
 	if (distrust_firmware)
 		ohci->flags |= OHCI_QUIRK_HUB_POWER;

drivers/usb/host/ohci-q.c

···
 	u32		info = 0;
 	int		is_out = usb_pipeout (urb->pipe);
 	int		periodic = 0;
+	int		i, this_sg_len, n;
+	struct scatterlist	*sg;
 
 	/* OHCI handles the bulk/interrupt data toggles itself.  We just
 	 * use the device toggle bits for resetting, and rely on the fact
···
 
 	list_add (&urb_priv->pending, &ohci->pending);
 
-	if (data_len)
-		data = urb->transfer_dma;
-	else
-		data = 0;
+	i = urb->num_mapped_sgs;
+	if (data_len > 0 && i > 0) {
+		sg = urb->sg;
+		data = sg_dma_address(sg);
+
+		/*
+		 * urb->transfer_buffer_length may be smaller than the
+		 * size of the scatterlist (or vice versa)
+		 */
+		this_sg_len = min_t(int, sg_dma_len(sg), data_len);
+	} else {
+		sg = NULL;
+		if (data_len)
+			data = urb->transfer_dma;
+		else
+			data = 0;
+		this_sg_len = data_len;
+	}
 
 	/* NOTE:  TD_CC is set so we can tell which TDs the HC processed by
 	 * using TD_CC_GET, as well as by seeing them on the done list.
···
 			? TD_T_TOGGLE | TD_CC | TD_DP_OUT
 			: TD_T_TOGGLE | TD_CC | TD_DP_IN;
 		/* TDs _could_ transfer up to 8K each */
-		while (data_len > 4096) {
-			td_fill (ohci, info, data, 4096, urb, cnt);
-			data += 4096;
-			data_len -= 4096;
+		for (;;) {
+			n = min(this_sg_len, 4096);
+
+			/* maybe avoid ED halt on final TD short read */
+			if (n >= data_len || (i == 1 && n >= this_sg_len)) {
+				if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
+					info |= TD_R;
+			}
+			td_fill(ohci, info, data, n, urb, cnt);
+			this_sg_len -= n;
+			data_len -= n;
+			data += n;
 			cnt++;
+
+			if (this_sg_len <= 0) {
+				if (--i <= 0 || data_len <= 0)
+					break;
+				sg = sg_next(sg);
+				data = sg_dma_address(sg);
+				this_sg_len = min_t(int, sg_dma_len(sg),
+						data_len);
+			}
 		}
-		/* maybe avoid ED halt on final TD short read */
-		if (!(urb->transfer_flags & URB_SHORT_NOT_OK))
-			info |= TD_R;
-		td_fill (ohci, info, data, data_len, urb, cnt);
-		cnt++;
 		if ((urb->transfer_flags & URB_ZERO_PACKET)
 				&& cnt < urb_priv->length) {
 			td_fill (ohci, info, 0, 0, urb, cnt);