USBNET: fix handling padding packet

Commit 638c5115a7949(USBNET: support DMA SG) introduces DMA SG
if the usb host controller is capable of building packet from
discontinuous buffers, but missed handling padding packet when
building DMA SG.

This patch attachs the pre-allocated padding packet at the
end of the sg list, so padding packet can be sent to device
if drivers require that.

Reported-by: David Laight <David.Laight@aculab.com>
Acked-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 7b331e613e02aec22c3ac225e3a99c53c5f0f822..bf94e10a37c8e0121d783fc54c1b565b57a7ce21 100644 (file)
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1241,7 +1241,9 @@ static int build_dma_sg(const struct sk_buff *skb, struct urb *urb)
        if (num_sgs == 1)
                return 0;
 
-       urb->sg = kmalloc(num_sgs * sizeof(struct scatterlist), GFP_ATOMIC);
+       /* reserve one for zero packet */
+       urb->sg = kmalloc((num_sgs + 1) * sizeof(struct scatterlist),
+                         GFP_ATOMIC);
        if (!urb->sg)
                return -ENOMEM;
 
@@ -1305,7 +1307,7 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
                if (build_dma_sg(skb, urb) < 0)
                        goto drop;
        }
-       entry->length = length = urb->transfer_buffer_length;
+       length = urb->transfer_buffer_length;
 
        /* don't assume the hardware handles USB_ZERO_PACKET
         * NOTE:  strictly conforming cdc-ether devices should expect
@@ -1317,15 +1319,18 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
        if (length % dev->maxpacket == 0) {
                if (!(info->flags & FLAG_SEND_ZLP)) {
                        if (!(info->flags & FLAG_MULTI_PACKET)) {
-                               urb->transfer_buffer_length++;
-                               if (skb_tailroom(skb)) {
+                               length++;
+                               if (skb_tailroom(skb) && !urb->num_sgs) {
                                        skb->data[skb->len] = 0;
                                        __skb_put(skb, 1);
-                               }
+                               } else if (urb->num_sgs)
+                                       sg_set_buf(&urb->sg[urb->num_sgs++],
+                                                       dev->padding_pkt, 1);
                        }
                } else
                        urb->transfer_flags |= URB_ZERO_PACKET;
        }
+       entry->length = urb->transfer_buffer_length = length;
 
        spin_lock_irqsave(&dev->txq.lock, flags);
        retval = usb_autopm_get_interface_async(dev->intf);
@@ -1509,6 +1514,7 @@ void usbnet_disconnect (struct usb_interface *intf)
 
        usb_kill_urb(dev->interrupt);
        usb_free_urb(dev->interrupt);
+       kfree(dev->padding_pkt);
 
        free_netdev(net);
 }
@@ -1679,9 +1685,16 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
        /* initialize max rx_qlen and tx_qlen */
        usbnet_update_max_qlen(dev);
 
+       if (dev->can_dma_sg && !(info->flags & FLAG_SEND_ZLP) &&
+               !(info->flags & FLAG_MULTI_PACKET)) {
+               dev->padding_pkt = kzalloc(1, GFP_KERNEL);
+               if (!dev->padding_pkt)
+                       goto out4;
+       }
+
        status = register_netdev (net);
        if (status)
-               goto out4;
+               goto out5;
        netif_info(dev, probe, dev->net,
                   "register '%s' at usb-%s-%s, %s, %pM\n",
                   udev->dev.driver->name,
@@ -1699,6 +1712,8 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 
        return 0;
 
+out5:
+       kfree(dev->padding_pkt);
 out4:
        usb_free_urb(dev->interrupt);
 out3:

diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 9cb2fe8ca944d5095043dd7b7ce71116a3fc21eb..e303eef94dd5cea92d16d7ae63aa35f5c3f1d4bb 100644 (file)
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -42,6 +42,7 @@ struct usbnet {
        struct usb_host_endpoint *status;
        unsigned                maxpacket;
        struct timer_list       delay;
+       const char              *padding_pkt;
 
        /* protocol/interface state */
        struct net_device       *net;