Move USB network drivers to drivers/net/usb.
[powerpc.git] / drivers / net / usb / rndis_host.c
diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
new file mode 100644 (file)
index 0000000..980e4aa
--- /dev/null
@@ -0,0 +1,727 @@
+/*
+ * Host Side support for RNDIS Networking Links
+ * Copyright (C) 2005 by David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+// #define     DEBUG                   // error path messages, extra info
+// #define     VERBOSE                 // more; success messages
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/workqueue.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+
+#include "usbnet.h"
+
+
+/*
+ * RNDIS is NDIS remoted over USB.  It's a MSFT variant of CDC ACM ... of
+ * course ACM was intended for modems, not Ethernet links!  USB's standard
+ * for Ethernet links is "CDC Ethernet", which is significantly simpler.
+ *
+ * NOTE that Microsoft's "RNDIS 1.0" specification is incomplete.  Issues
+ * include:
+ *    - Power management in particular relies on information that's scattered
+ *     through other documentation, and which is incomplete or incorrect even
+ *     there.
+ *    - There are various undocumented protocol requirements, such as the
+ *     need to send unused garbage in control-OUT messages.
+ *    - In some cases, MS-Windows will emit undocumented requests; this
+ *     matters more to peripheral implementations than host ones.
+ *
+ * Moreover there's a no-open-specs variant of RNDIS called "ActiveSync".
+ *
+ * For these reasons and others, ** USE OF RNDIS IS STRONGLY DISCOURAGED ** in
+ * favor of such non-proprietary alternatives as CDC Ethernet or the newer (and
+ * currently rare) "Ethernet Emulation Model" (EEM).
+ */
+
+/*
+ * CONTROL uses CDC "encapsulated commands" with funky notifications.
+ *  - control-out:  SEND_ENCAPSULATED
+ *  - interrupt-in:  RESPONSE_AVAILABLE
+ *  - control-in:  GET_ENCAPSULATED
+ *
+ * We'll try to ignore the RESPONSE_AVAILABLE notifications.
+ *
+ * REVISIT some RNDIS implementations seem to have curious issues still
+ * to be resolved.
+ */
+struct rndis_msg_hdr {
+       __le32  msg_type;                       /* RNDIS_MSG_* */
+       __le32  msg_len;
+       // followed by data that varies between messages
+       __le32  request_id;
+       __le32  status;
+       // ... and more
+} __attribute__ ((packed));
+
+/* MS-Windows uses this strange size, but RNDIS spec says 1024 minimum */
+#define        CONTROL_BUFFER_SIZE             1025
+
+/* RNDIS defines an (absurdly huge) 10 second control timeout,
+ * but ActiveSync seems to use a more usual 5 second timeout
+ * (which matches the USB 2.0 spec).
+ */
+#define        RNDIS_CONTROL_TIMEOUT_MS        (5 * 1000)
+
+
+#define ccpu2 __constant_cpu_to_le32
+
+#define RNDIS_MSG_COMPLETION   ccpu2(0x80000000)
+
+/* codes for "msg_type" field of rndis messages;
+ * only the data channel uses packet messages (maybe batched);
+ * everything else goes on the control channel.
+ */
+#define RNDIS_MSG_PACKET       ccpu2(0x00000001)       /* 1-N packets */
+#define RNDIS_MSG_INIT         ccpu2(0x00000002)
+#define RNDIS_MSG_INIT_C       (RNDIS_MSG_INIT|RNDIS_MSG_COMPLETION)
+#define RNDIS_MSG_HALT         ccpu2(0x00000003)
+#define RNDIS_MSG_QUERY                ccpu2(0x00000004)
+#define RNDIS_MSG_QUERY_C      (RNDIS_MSG_QUERY|RNDIS_MSG_COMPLETION)
+#define RNDIS_MSG_SET          ccpu2(0x00000005)
+#define RNDIS_MSG_SET_C                (RNDIS_MSG_SET|RNDIS_MSG_COMPLETION)
+#define RNDIS_MSG_RESET                ccpu2(0x00000006)
+#define RNDIS_MSG_RESET_C      (RNDIS_MSG_RESET|RNDIS_MSG_COMPLETION)
+#define RNDIS_MSG_INDICATE     ccpu2(0x00000007)
+#define RNDIS_MSG_KEEPALIVE    ccpu2(0x00000008)
+#define RNDIS_MSG_KEEPALIVE_C  (RNDIS_MSG_KEEPALIVE|RNDIS_MSG_COMPLETION)
+
+/* codes for "status" field of completion messages */
+#define        RNDIS_STATUS_SUCCESS            ccpu2(0x00000000)
+#define        RNDIS_STATUS_FAILURE            ccpu2(0xc0000001)
+#define        RNDIS_STATUS_INVALID_DATA       ccpu2(0xc0010015)
+#define        RNDIS_STATUS_NOT_SUPPORTED      ccpu2(0xc00000bb)
+#define        RNDIS_STATUS_MEDIA_CONNECT      ccpu2(0x4001000b)
+#define        RNDIS_STATUS_MEDIA_DISCONNECT   ccpu2(0x4001000c)
+
+
+struct rndis_data_hdr {
+       __le32  msg_type;               /* RNDIS_MSG_PACKET */
+       __le32  msg_len;                // rndis_data_hdr + data_len + pad
+       __le32  data_offset;            // 36 -- right after header
+       __le32  data_len;               // ... real packet size
+
+       __le32  oob_data_offset;        // zero
+       __le32  oob_data_len;           // zero
+       __le32  num_oob;                // zero
+       __le32  packet_data_offset;     // zero
+
+       __le32  packet_data_len;        // zero
+       __le32  vc_handle;              // zero
+       __le32  reserved;               // zero
+} __attribute__ ((packed));
+
+struct rndis_init {            /* OUT */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_INIT */
+       __le32  msg_len;                        // 24
+       __le32  request_id;
+       __le32  major_version;                  // of rndis (1.0)
+       __le32  minor_version;
+       __le32  max_transfer_size;
+} __attribute__ ((packed));
+
+struct rndis_init_c {          /* IN */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_INIT_C */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  status;
+       __le32  major_version;                  // of rndis (1.0)
+       __le32  minor_version;
+       __le32  device_flags;
+       __le32  medium;                         // zero == 802.3
+       __le32  max_packets_per_message;
+       __le32  max_transfer_size;
+       __le32  packet_alignment;               // max 7; (1<<n) bytes
+       __le32  af_list_offset;                 // zero
+       __le32  af_list_size;                   // zero
+} __attribute__ ((packed));
+
+struct rndis_halt {            /* OUT (no reply) */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_HALT */
+       __le32  msg_len;
+       __le32  request_id;
+} __attribute__ ((packed));
+
+struct rndis_query {           /* OUT */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_QUERY */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  oid;
+       __le32  len;
+       __le32  offset;
+/*?*/  __le32  handle;                         // zero
+} __attribute__ ((packed));
+
+struct rndis_query_c {         /* IN */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_QUERY_C */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  status;
+       __le32  len;
+       __le32  offset;
+} __attribute__ ((packed));
+
+struct rndis_set {             /* OUT */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_SET */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  oid;
+       __le32  len;
+       __le32  offset;
+/*?*/  __le32  handle;                         // zero
+} __attribute__ ((packed));
+
+struct rndis_set_c {           /* IN */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_SET_C */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  status;
+} __attribute__ ((packed));
+
+struct rndis_reset {           /* IN */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_RESET */
+       __le32  msg_len;
+       __le32  reserved;
+} __attribute__ ((packed));
+
+struct rndis_reset_c {         /* OUT */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_RESET_C */
+       __le32  msg_len;
+       __le32  status;
+       __le32  addressing_lost;
+} __attribute__ ((packed));
+
+struct rndis_indicate {                /* IN (unrequested) */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_INDICATE */
+       __le32  msg_len;
+       __le32  status;
+       __le32  length;
+       __le32  offset;
+/**/   __le32  diag_status;
+       __le32  error_offset;
+/**/   __le32  message;
+} __attribute__ ((packed));
+
+struct rndis_keepalive {       /* OUT (optionally IN) */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_KEEPALIVE */
+       __le32  msg_len;
+       __le32  request_id;
+} __attribute__ ((packed));
+
+struct rndis_keepalive_c {     /* IN (optionally OUT) */
+       // header and:
+       __le32  msg_type;                       /* RNDIS_MSG_KEEPALIVE_C */
+       __le32  msg_len;
+       __le32  request_id;
+       __le32  status;
+} __attribute__ ((packed));
+
+/* NOTE:  about 30 OIDs are "mandatory" for peripherals to support ... and
+ * there are gobs more that may optionally be supported.  We'll avoid as much
+ * of that mess as possible.
+ */
+#define OID_802_3_PERMANENT_ADDRESS    ccpu2(0x01010101)
+#define OID_GEN_MAXIMUM_FRAME_SIZE     ccpu2(0x00010106)
+#define OID_GEN_CURRENT_PACKET_FILTER  ccpu2(0x0001010e)
+
+/*
+ * RNDIS notifications from device: command completion; "reverse"
+ * keepalives; etc
+ */
+static void rndis_status(struct usbnet *dev, struct urb *urb)
+{
+       devdbg(dev, "rndis status urb, len %d stat %d",
+               urb->actual_length, urb->status);
+       // FIXME for keepalives, respond immediately (asynchronously)
+       // if not an RNDIS status, do like cdc_status(dev,urb) does
+}
+
+/*
+ * RPC done RNDIS-style.  Caller guarantees:
+ * - message is properly byteswapped
+ * - there's no other request pending
+ * - buf can hold up to 1KB response (required by RNDIS spec)
+ * On return, the first few entries are already byteswapped.
+ *
+ * Call context is likely probe(), before interface name is known,
+ * which is why we won't try to use it in the diagnostics.
+ */
+static int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf)
+{
+       struct cdc_state        *info = (void *) &dev->data;
+       int                     master_ifnum;
+       int                     retval;
+       unsigned                count;
+       __le32                  rsp;
+       u32                     xid = 0, msg_len, request_id;
+
+       /* REVISIT when this gets called from contexts other than probe() or
+        * disconnect(): either serialize, or dispatch responses on xid
+        */
+
+       /* Issue the request; xid is unique, don't bother byteswapping it */
+       if (likely(buf->msg_type != RNDIS_MSG_HALT
+                       && buf->msg_type != RNDIS_MSG_RESET)) {
+               xid = dev->xid++;
+               if (!xid)
+                       xid = dev->xid++;
+               buf->request_id = (__force __le32) xid;
+       }
+       master_ifnum = info->control->cur_altsetting->desc.bInterfaceNumber;
+       retval = usb_control_msg(dev->udev,
+               usb_sndctrlpipe(dev->udev, 0),
+               USB_CDC_SEND_ENCAPSULATED_COMMAND,
+               USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+               0, master_ifnum,
+               buf, le32_to_cpu(buf->msg_len),
+               RNDIS_CONTROL_TIMEOUT_MS);
+       if (unlikely(retval < 0 || xid == 0))
+               return retval;
+
+       // FIXME Seems like some devices discard responses when
+       // we time out and cancel our "get response" requests...
+       // so, this is fragile.  Probably need to poll for status.
+
+       /* ignore status endpoint, just poll the control channel;
+        * the request probably completed immediately
+        */
+       rsp = buf->msg_type | RNDIS_MSG_COMPLETION;
+       for (count = 0; count < 10; count++) {
+               memset(buf, 0, CONTROL_BUFFER_SIZE);
+               retval = usb_control_msg(dev->udev,
+                       usb_rcvctrlpipe(dev->udev, 0),
+                       USB_CDC_GET_ENCAPSULATED_RESPONSE,
+                       USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+                       0, master_ifnum,
+                       buf, CONTROL_BUFFER_SIZE,
+                       RNDIS_CONTROL_TIMEOUT_MS);
+               if (likely(retval >= 8)) {
+                       msg_len = le32_to_cpu(buf->msg_len);
+                       request_id = (__force u32) buf->request_id;
+                       if (likely(buf->msg_type == rsp)) {
+                               if (likely(request_id == xid)) {
+                                       if (unlikely(rsp == RNDIS_MSG_RESET_C))
+                                               return 0;
+                                       if (likely(RNDIS_STATUS_SUCCESS
+                                                       == buf->status))
+                                               return 0;
+                                       dev_dbg(&info->control->dev,
+                                               "rndis reply status %08x\n",
+                                               le32_to_cpu(buf->status));
+                                       return -EL3RST;
+                               }
+                               dev_dbg(&info->control->dev,
+                                       "rndis reply id %d expected %d\n",
+                                       request_id, xid);
+                               /* then likely retry */
+                       } else switch (buf->msg_type) {
+                       case RNDIS_MSG_INDICATE: {      /* fault */
+                               // struct rndis_indicate *msg = (void *)buf;
+                               dev_info(&info->control->dev,
+                                       "rndis fault indication\n");
+                               }
+                               break;
+                       case RNDIS_MSG_KEEPALIVE: {     /* ping */
+                               struct rndis_keepalive_c *msg = (void *)buf;
+
+                               msg->msg_type = RNDIS_MSG_KEEPALIVE_C;
+                               msg->msg_len = ccpu2(sizeof *msg);
+                               msg->status = RNDIS_STATUS_SUCCESS;
+                               retval = usb_control_msg(dev->udev,
+                                       usb_sndctrlpipe(dev->udev, 0),
+                                       USB_CDC_SEND_ENCAPSULATED_COMMAND,
+                                       USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+                                       0, master_ifnum,
+                                       msg, sizeof *msg,
+                                       RNDIS_CONTROL_TIMEOUT_MS);
+                               if (unlikely(retval < 0))
+                                       dev_dbg(&info->control->dev,
+                                               "rndis keepalive err %d\n",
+                                               retval);
+                               }
+                               break;
+                       default:
+                               dev_dbg(&info->control->dev,
+                                       "unexpected rndis msg %08x len %d\n",
+                                       le32_to_cpu(buf->msg_type), msg_len);
+                       }
+               } else {
+                       /* device probably issued a protocol stall; ignore */
+                       dev_dbg(&info->control->dev,
+                               "rndis response error, code %d\n", retval);
+               }
+               msleep(2);
+       }
+       dev_dbg(&info->control->dev, "rndis response timeout\n");
+       return -ETIMEDOUT;
+}
+
+/*
+ * rndis_query:
+ *
+ * Performs a query for @oid along with 0 or more bytes of payload as
+ * specified by @in_len. If @reply_len is not set to -1 then the reply
+ * length is checked against this value, resulting in an error if it
+ * doesn't match.
+ *
+ * NOTE: Adding a payload exactly or greater than the size of the expected
+ * response payload is an evident requirement MSFT added for ActiveSync.
+ *
+ * The only exception is for OIDs that return a variably sized response,
+ * in which case no payload should be added.  This undocumented (and
+ * nonsensical!) issue was found by sniffing protocol requests from the
+ * ActiveSync 4.1 Windows driver.
+ */
+static int rndis_query(struct usbnet *dev, struct usb_interface *intf,
+               void *buf, u32 oid, u32 in_len,
+               void **reply, int *reply_len)
+{
+       int retval;
+       union {
+               void                    *buf;
+               struct rndis_msg_hdr    *header;
+               struct rndis_query      *get;
+               struct rndis_query_c    *get_c;
+       } u;
+       u32 off, len;
+
+       u.buf = buf;
+
+       memset(u.get, 0, sizeof *u.get + in_len);
+       u.get->msg_type = RNDIS_MSG_QUERY;
+       u.get->msg_len = cpu_to_le32(sizeof *u.get + in_len);
+       u.get->oid = oid;
+       u.get->len = cpu_to_le32(in_len);
+       u.get->offset = ccpu2(20);
+
+       retval = rndis_command(dev, u.header);
+       if (unlikely(retval < 0)) {
+               dev_err(&intf->dev, "RNDIS_MSG_QUERY(0x%08x) failed, %d\n",
+                               oid, retval);
+               return retval;
+       }
+
+       off = le32_to_cpu(u.get_c->offset);
+       len = le32_to_cpu(u.get_c->len);
+       if (unlikely((8 + off + len) > CONTROL_BUFFER_SIZE))
+               goto response_error;
+
+       if (*reply_len != -1 && len != *reply_len)
+               goto response_error;
+
+       *reply = (unsigned char *) &u.get_c->request_id + off;
+       *reply_len = len;
+
+       return retval;
+
+response_error:
+       dev_err(&intf->dev, "RNDIS_MSG_QUERY(0x%08x) "
+                       "invalid response - off %d len %d\n",
+               oid, off, len);
+       return -EDOM;
+}
+
+static int rndis_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+       int                     retval;
+       struct net_device       *net = dev->net;
+       struct cdc_state        *info = (void *) &dev->data;
+       union {
+               void                    *buf;
+               struct rndis_msg_hdr    *header;
+               struct rndis_init       *init;
+               struct rndis_init_c     *init_c;
+               struct rndis_query      *get;
+               struct rndis_query_c    *get_c;
+               struct rndis_set        *set;
+               struct rndis_set_c      *set_c;
+       } u;
+       u32                     tmp;
+       int                     reply_len;
+       unsigned char           *bp;
+
+       /* we can't rely on i/o from stack working, or stack allocation */
+       u.buf = kmalloc(CONTROL_BUFFER_SIZE, GFP_KERNEL);
+       if (!u.buf)
+               return -ENOMEM;
+       retval = usbnet_generic_cdc_bind(dev, intf);
+       if (retval < 0)
+               goto fail;
+
+       u.init->msg_type = RNDIS_MSG_INIT;
+       u.init->msg_len = ccpu2(sizeof *u.init);
+       u.init->major_version = ccpu2(1);
+       u.init->minor_version = ccpu2(0);
+
+       /* max transfer (in spec) is 0x4000 at full speed, but for
+        * TX we'll stick to one Ethernet packet plus RNDIS framing.
+        * For RX we handle drivers that zero-pad to end-of-packet.
+        * Don't let userspace change these settings.
+        *
+        * NOTE: there still seems to be wierdness here, as if we need
+        * to do some more things to make sure WinCE targets accept this.
+        * They default to jumbograms of 8KB or 16KB, which is absurd
+        * for such low data rates and which is also more than Linux
+        * can usually expect to allocate for SKB data...
+        */
+       net->hard_header_len += sizeof (struct rndis_data_hdr);
+       dev->hard_mtu = net->mtu + net->hard_header_len;
+
+       dev->rx_urb_size = dev->hard_mtu + (dev->maxpacket + 1);
+       dev->rx_urb_size &= ~(dev->maxpacket - 1);
+       u.init->max_transfer_size = cpu_to_le32(dev->rx_urb_size);
+
+       net->change_mtu = NULL;
+       retval = rndis_command(dev, u.header);
+       if (unlikely(retval < 0)) {
+               /* it might not even be an RNDIS device!! */
+               dev_err(&intf->dev, "RNDIS init failed, %d\n", retval);
+               goto fail_and_release;
+       }
+       tmp = le32_to_cpu(u.init_c->max_transfer_size);
+       if (tmp < dev->hard_mtu) {
+               dev_err(&intf->dev,
+                       "dev can't take %u byte packets (max %u)\n",
+                       dev->hard_mtu, tmp);
+               goto fail_and_release;
+       }
+
+       /* REVISIT:  peripheral "alignment" request is ignored ... */
+       dev_dbg(&intf->dev,
+               "hard mtu %u (%u from dev), rx buflen %Zu, align %d\n",
+               dev->hard_mtu, tmp, dev->rx_urb_size,
+               1 << le32_to_cpu(u.init_c->packet_alignment));
+
+       /* Get designated host ethernet address */
+       reply_len = ETH_ALEN;
+       retval = rndis_query(dev, intf, u.buf, OID_802_3_PERMANENT_ADDRESS,
+                       48, (void **) &bp, &reply_len);
+       if (unlikely(retval< 0)) {
+               dev_err(&intf->dev, "rndis get ethaddr, %d\n", retval);
+               goto fail_and_release;
+       }
+       memcpy(net->dev_addr, bp, ETH_ALEN);
+
+       /* set a nonzero filter to enable data transfers */
+       memset(u.set, 0, sizeof *u.set);
+       u.set->msg_type = RNDIS_MSG_SET;
+       u.set->msg_len = ccpu2(4 + sizeof *u.set);
+       u.set->oid = OID_GEN_CURRENT_PACKET_FILTER;
+       u.set->len = ccpu2(4);
+       u.set->offset = ccpu2((sizeof *u.set) - 8);
+       *(__le32 *)(u.buf + sizeof *u.set) = ccpu2(DEFAULT_FILTER);
+
+       retval = rndis_command(dev, u.header);
+       if (unlikely(retval < 0)) {
+               dev_err(&intf->dev, "rndis set packet filter, %d\n", retval);
+               goto fail_and_release;
+       }
+
+       retval = 0;
+
+       kfree(u.buf);
+       return retval;
+
+fail_and_release:
+       usb_set_intfdata(info->data, NULL);
+       usb_driver_release_interface(driver_of(intf), info->data);
+       info->data = NULL;
+fail:
+       kfree(u.buf);
+       return retval;
+}
+
+static void rndis_unbind(struct usbnet *dev, struct usb_interface *intf)
+{
+       struct rndis_halt       *halt;
+
+       /* try to clear any rndis state/activity (no i/o from stack!) */
+       halt = kzalloc(sizeof *halt, GFP_KERNEL);
+       if (halt) {
+               halt->msg_type = RNDIS_MSG_HALT;
+               halt->msg_len = ccpu2(sizeof *halt);
+               (void) rndis_command(dev, (void *)halt);
+               kfree(halt);
+       }
+
+       return usbnet_cdc_unbind(dev, intf);
+}
+
+/*
+ * DATA -- host must not write zlps
+ */
+static int rndis_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
+{
+       /* peripheral may have batched packets to us... */
+       while (likely(skb->len)) {
+               struct rndis_data_hdr   *hdr = (void *)skb->data;
+               struct sk_buff          *skb2;
+               u32                     msg_len, data_offset, data_len;
+
+               msg_len = le32_to_cpu(hdr->msg_len);
+               data_offset = le32_to_cpu(hdr->data_offset);
+               data_len = le32_to_cpu(hdr->data_len);
+
+               /* don't choke if we see oob, per-packet data, etc */
+               if (unlikely(hdr->msg_type != RNDIS_MSG_PACKET
+                               || skb->len < msg_len
+                               || (data_offset + data_len + 8) > msg_len)) {
+                       dev->stats.rx_frame_errors++;
+                       devdbg(dev, "bad rndis message %d/%d/%d/%d, len %d",
+                               le32_to_cpu(hdr->msg_type),
+                               msg_len, data_offset, data_len, skb->len);
+                       return 0;
+               }
+               skb_pull(skb, 8 + data_offset);
+
+               /* at most one packet left? */
+               if (likely((data_len - skb->len) <= sizeof *hdr)) {
+                       skb_trim(skb, data_len);
+                       break;
+               }
+
+               /* try to return all the packets in the batch */
+               skb2 = skb_clone(skb, GFP_ATOMIC);
+               if (unlikely(!skb2))
+                       break;
+               skb_pull(skb, msg_len - sizeof *hdr);
+               skb_trim(skb2, data_len);
+               usbnet_skb_return(dev, skb2);
+       }
+
+       /* caller will usbnet_skb_return the remaining packet */
+       return 1;
+}
+
+static struct sk_buff *
+rndis_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
+{
+       struct rndis_data_hdr   *hdr;
+       struct sk_buff          *skb2;
+       unsigned                len = skb->len;
+
+       if (likely(!skb_cloned(skb))) {
+               int     room = skb_headroom(skb);
+
+               /* enough head room as-is? */
+               if (unlikely((sizeof *hdr) <= room))
+                       goto fill;
+
+               /* enough room, but needs to be readjusted? */
+               room += skb_tailroom(skb);
+               if (likely((sizeof *hdr) <= room)) {
+                       skb->data = memmove(skb->head + sizeof *hdr,
+                                           skb->data, len);
+                       skb_set_tail_pointer(skb, len);
+                       goto fill;
+               }
+       }
+
+       /* create a new skb, with the correct size (and tailpad) */
+       skb2 = skb_copy_expand(skb, sizeof *hdr, 1, flags);
+       dev_kfree_skb_any(skb);
+       if (unlikely(!skb2))
+               return skb2;
+       skb = skb2;
+
+       /* fill out the RNDIS header.  we won't bother trying to batch
+        * packets; Linux minimizes wasted bandwidth through tx queues.
+        */
+fill:
+       hdr = (void *) __skb_push(skb, sizeof *hdr);
+       memset(hdr, 0, sizeof *hdr);
+       hdr->msg_type = RNDIS_MSG_PACKET;
+       hdr->msg_len = cpu_to_le32(skb->len);
+       hdr->data_offset = ccpu2(sizeof(*hdr) - 8);
+       hdr->data_len = cpu_to_le32(len);
+
+       /* FIXME make the last packet always be short ... */
+       return skb;
+}
+
+
+static const struct driver_info        rndis_info = {
+       .description =  "RNDIS device",
+       .flags =        FLAG_ETHER | FLAG_FRAMING_RN | FLAG_NO_SETINT,
+       .bind =         rndis_bind,
+       .unbind =       rndis_unbind,
+       .status =       rndis_status,
+       .rx_fixup =     rndis_rx_fixup,
+       .tx_fixup =     rndis_tx_fixup,
+};
+
+#undef ccpu2
+
+
+/*-------------------------------------------------------------------------*/
+
+static const struct usb_device_id      products [] = {
+{
+       /* RNDIS is MSFT's un-official variant of CDC ACM */
+       USB_INTERFACE_INFO(USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
+       .driver_info = (unsigned long) &rndis_info,
+}, {
+       /* "ActiveSync" is an undocumented variant of RNDIS, used in WM5 */
+       USB_INTERFACE_INFO(USB_CLASS_MISC, 1, 1),
+       .driver_info = (unsigned long) &rndis_info,
+},
+       { },            // END
+};
+MODULE_DEVICE_TABLE(usb, products);
+
+static struct usb_driver rndis_driver = {
+       .name =         "rndis_host",
+       .id_table =     products,
+       .probe =        usbnet_probe,
+       .disconnect =   usbnet_disconnect,
+       .suspend =      usbnet_suspend,
+       .resume =       usbnet_resume,
+};
+
+static int __init rndis_init(void)
+{
+       return usb_register(&rndis_driver);
+}
+module_init(rndis_init);
+
+static void __exit rndis_exit(void)
+{
+       usb_deregister(&rndis_driver);
+}
+module_exit(rndis_exit);
+
+MODULE_AUTHOR("David Brownell");
+MODULE_DESCRIPTION("USB Host side RNDIS driver");
+MODULE_LICENSE("GPL");