usb: gadget: u_ether: prepare for NCM

NCM is a Network Control Model, subclass of USB CDC class,
specification is available at http://www.usb.org/developers/devclass_docs

This patch makes possible for u_ether to use multiply of wMaxPacketSize
predefined size transfers without ZLP (Zero Length Packet), required
by NCM spec.

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 16 insertions, 2 deletions

diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c
index cb23355f52d3..a7826a6dcd8c 100644
--- a/drivers/usb/gadget/u_ether.c
+++ b/drivers/usb/gadget/u_ether.c
@@ -240,6 +240,9 @@ rx_submit(struct eth_dev *dev, struct usb_request *req, gfp_t gfp_flags)
         size += out->maxpacket - 1;
         size -= size % out->maxpacket;
 
+        if (dev->port_usb->is_fixed)
+                size = max(size, dev->port_usb->fixed_out_len);
+
         skb = alloc_skb(size + NET_IP_ALIGN, gfp_flags);
         if (skb == NULL) {
                 DBG(dev, "no rx skb\n");
@@ -578,12 +581,19 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
         req->context = skb;
         req->complete = tx_complete;
 
+        /* NCM requires no zlp if transfer is dwNtbInMaxSize */
+        if (dev->port_usb->is_fixed &&
+            length == dev->port_usb->fixed_in_len &&
+            (length % in->maxpacket) == 0)
+                req->zero = 0;
+        else
+                req->zero = 1;
+
         /* use zlp framing on tx for strict CDC-Ether conformance,
          * though any robust network rx path ignores extra padding.
          * and some hardware doesn't like to write zlps.
          */
-        req->zero = 1;
-        if (!dev->zlp && (length % in->maxpacket) == 0)
+        if (req->zero && !dev->zlp && (length % in->maxpacket) == 0)
                 length++;
 
         req->length = length;
diff --git a/drivers/usb/gadget/u_ether.h b/drivers/usb/gadget/u_ether.h
index 3c8c0c9f9d72..75219708abb8 100644
--- a/drivers/usb/gadget/u_ether.h
+++ b/drivers/usb/gadget/u_ether.h
@@ -62,6 +62,10 @@ struct gether {
 
         /* hooks for added framing, as needed for RNDIS and EEM. */
         u32                             header_len;
+        /* NCM requires fixed size bundles */
+        bool                            is_fixed;
+        u32                             fixed_out_len;
+        u32                             fixed_in_len;
         struct sk_buff                  *(*wrap)(struct gether *port,
                                                 struct sk_buff *skb);
         int                             (*unwrap)(struct gether *port,