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+/*
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+ * USB CDC EEM network interface driver
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+ * Copyright (C) 2009 Oberthur Technologies
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+ * by Omar Laazimani, Olivier Condemine
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation; either version 2 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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+ */
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+
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+#include <linux/module.h>
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+#include <linux/init.h>
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+#include <linux/netdevice.h>
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+#include <linux/etherdevice.h>
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+#include <linux/ctype.h>
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+#include <linux/ethtool.h>
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+#include <linux/workqueue.h>
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+#include <linux/mii.h>
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+#include <linux/usb.h>
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+#include <linux/crc32.h>
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+#include <linux/usb/cdc.h>
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+#include <linux/usb/usbnet.h>
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+
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+
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+/*
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+ * This driver is an implementation of the CDC "Ethernet Emulation
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+ * Model" (EEM) specification, which encapsulates Ethernet frames
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+ * for transport over USB using a simpler USB device model than the
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+ * previous CDC "Ethernet Control Model" (ECM, or "CDC Ethernet").
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+ *
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+ * For details, see www.usb.org/developers/devclass_docs/CDC_EEM10.pdf
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+ *
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+ * This version has been tested with GIGAntIC WuaoW SIM Smart Card on 2.6.24,
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+ * 2.6.27 and 2.6.30rc2 kernel.
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+ * It has also been validated on Openmoko Om 2008.12 (based on 2.6.24 kernel).
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+ * build on 23-April-2009
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+ */
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+
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+#define EEM_HEAD 2 /* 2 byte header */
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+
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+/*-------------------------------------------------------------------------*/
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+
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+static void eem_linkcmd_complete(struct urb *urb)
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+{
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+ dev_kfree_skb(urb->context);
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+ usb_free_urb(urb);
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+}
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+
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+static void eem_linkcmd(struct usbnet *dev, struct sk_buff *skb)
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+{
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+ struct urb *urb;
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+ int status;
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+
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+ urb = usb_alloc_urb(0, GFP_ATOMIC);
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+ if (!urb)
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+ goto fail;
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+
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+ usb_fill_bulk_urb(urb, dev->udev, dev->out,
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+ skb->data, skb->len, eem_linkcmd_complete, skb);
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+
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+ status = usb_submit_urb(urb, GFP_ATOMIC);
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+ if (status) {
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+ usb_free_urb(urb);
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+fail:
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+ dev_kfree_skb(skb);
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+ devwarn(dev, "link cmd failure\n");
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+ return;
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+ }
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+}
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+
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+static int eem_bind(struct usbnet *dev, struct usb_interface *intf)
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+{
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+ int status = 0;
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+
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+ status = usbnet_get_endpoints(dev, intf);
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+ if (status < 0) {
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+ usb_set_intfdata(intf, NULL);
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+ usb_driver_release_interface(driver_of(intf), intf);
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+ return status;
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+ }
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+
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+ /* no jumbogram (16K) support for now */
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+
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+ dev->net->hard_header_len += EEM_HEAD + ETH_FCS_LEN;
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+
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+ return 0;
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+}
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+
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+/*
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+ * EEM permits packing multiple Ethernet frames into USB transfers
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+ * (a "bundle"), but for TX we don't try to do that.
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+ */
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+static struct sk_buff *eem_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
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+ gfp_t flags)
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+{
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+ struct sk_buff *skb2 = NULL;
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+ u16 len = skb->len;
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+ u32 crc = 0;
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+ int padlen = 0;
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+
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+ /* When ((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket) is
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+ * zero, stick two bytes of zero length EEM packet on the end.
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+ * Else the framework would add invalid single byte padding,
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+ * since it can't know whether ZLPs will be handled right by
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+ * all the relevant hardware and software.
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+ */
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+ if (!((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket))
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+ padlen += 2;
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+
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+ if (!skb_cloned(skb)) {
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+ int headroom = skb_headroom(skb);
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+ int tailroom = skb_tailroom(skb);
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+
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+ if ((tailroom >= ETH_FCS_LEN + padlen)
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+ && (headroom >= EEM_HEAD))
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+ goto done;
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+
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+ if ((headroom + tailroom)
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+ > (EEM_HEAD + ETH_FCS_LEN + padlen)) {
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+ skb->data = memmove(skb->head +
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+ EEM_HEAD,
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+ skb->data,
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+ skb->len);
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+ skb_set_tail_pointer(skb, len);
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+ goto done;
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+ }
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+ }
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+
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+ skb2 = skb_copy_expand(skb, EEM_HEAD, ETH_FCS_LEN + padlen, flags);
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+ if (!skb2)
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+ return NULL;
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+
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+ dev_kfree_skb_any(skb);
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+ skb = skb2;
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+
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+done:
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+ /* we don't use the "no Ethernet CRC" option */
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+ crc = crc32_le(~0, skb->data, skb->len);
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+ crc = ~crc;
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+
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+ put_unaligned_le32(crc, skb_put(skb, 4));
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+
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+ /* EEM packet header format:
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+ * b0..13: length of ethernet frame
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+ * b14: bmCRC (1 == valid Ethernet CRC)
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+ * b15: bmType (0 == data)
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+ */
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+ len = skb->len;
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+ put_unaligned_le16(BIT(14) | len, skb_push(skb, 2));
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+
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+ /* Bundle a zero length EEM packet if needed */
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+ if (padlen)
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+ put_unaligned_le16(0, skb_put(skb, 2));
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+
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+ return skb;
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+}
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+
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+static int eem_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
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+{
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+ /*
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+ * Our task here is to strip off framing, leaving skb with one
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+ * data frame for the usbnet framework code to process. But we
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+ * may have received multiple EEM payloads, or command payloads.
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+ * So we must process _everything_ as if it's a header, except
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+ * maybe the last data payload
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+ *
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+ * REVISIT the framework needs updating so that when we consume
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+ * all payloads (the last or only message was a command, or a
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+ * zero length EEM packet) that is not accounted as an rx_error.
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+ */
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+ do {
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+ struct sk_buff *skb2 = NULL;
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+ u16 header;
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+ u16 len = 0;
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+
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+ /* incomplete EEM header? */
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+ if (skb->len < EEM_HEAD)
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+ return 0;
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+
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+ /*
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+ * EEM packet header format:
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+ * b0..14: EEM type dependant (Data or Command)
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+ * b15: bmType
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+ */
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+ header = get_unaligned_le16(skb->data);
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+ skb_pull(skb, EEM_HEAD);
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+
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+ /*
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+ * The bmType bit helps to denote when EEM
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+ * packet is data or command :
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+ * bmType = 0 : EEM data payload
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+ * bmType = 1 : EEM (link) command
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+ */
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+ if (header & BIT(15)) {
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+ u16 bmEEMCmd;
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+
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+ /*
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+ * EEM (link) command packet:
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+ * b0..10: bmEEMCmdParam
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+ * b11..13: bmEEMCmd
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+ * b14: bmReserved (must be 0)
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+ * b15: 1 (EEM command)
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+ */
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+ if (header & BIT(14)) {
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+ devdbg(dev, "reserved command %04x\n", header);
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+ continue;
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+ }
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+
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+ bmEEMCmd = (header >> 11) & 0x7;
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+ switch (bmEEMCmd) {
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+
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+ /* Responding to echo requests is mandatory. */
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+ case 0: /* Echo command */
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+ len = header & 0x7FF;
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+
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+ /* bogus command? */
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+ if (skb->len < len)
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+ return 0;
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+
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+ skb2 = skb_clone(skb, GFP_ATOMIC);
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+ if (unlikely(!skb2))
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+ goto next;
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+ skb_trim(skb2, len);
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+ put_unaligned_le16(BIT(15) | (1 << 11) | len,
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+ skb_push(skb2, 2));
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+ eem_linkcmd(dev, skb2);
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+ break;
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+
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+ /*
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+ * Host may choose to ignore hints.
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+ * - suspend: peripheral ready to suspend
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+ * - response: suggest N millisec polling
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+ * - response complete: suggest N sec polling
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+ */
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+ case 2: /* Suspend hint */
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+ case 3: /* Response hint */
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+ case 4: /* Response complete hint */
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+ continue;
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+
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+ /*
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+ * Hosts should never receive host-to-peripheral
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+ * or reserved command codes; or responses to an
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+ * echo command we didn't send.
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+ */
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+ case 1: /* Echo response */
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+ case 5: /* Tickle */
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+ default: /* reserved */
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+ devwarn(dev, "unexpected link command %d\n",
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+ bmEEMCmd);
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+ continue;
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+ }
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+
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+ } else {
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+ u32 crc, crc2;
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+ int is_last;
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+
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+ /* zero length EEM packet? */
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+ if (header == 0)
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+ continue;
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+
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+ /*
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+ * EEM data packet header :
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+ * b0..13: length of ethernet frame
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+ * b14: bmCRC
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+ * b15: 0 (EEM data)
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+ */
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+ len = header & 0x3FFF;
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+
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+ /* bogus EEM payload? */
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+ if (skb->len < len)
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+ return 0;
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+
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+ /* bogus ethernet frame? */
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+ if (len < (ETH_HLEN + ETH_FCS_LEN))
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+ goto next;
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+
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+ /*
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+ * Treat the last payload differently: framework
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+ * code expects our "fixup" to have stripped off
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+ * headers, so "skb" is a data packet (or error).
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+ * Else if it's not the last payload, keep "skb"
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+ * for further processing.
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+ */
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+ is_last = (len == skb->len);
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+ if (is_last)
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+ skb2 = skb;
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+ else {
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+ skb2 = skb_clone(skb, GFP_ATOMIC);
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+ if (unlikely(!skb2))
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+ return 0;
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+ }
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+
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+ crc = get_unaligned_le32(skb2->data
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+ + len - ETH_FCS_LEN);
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+ skb_trim(skb2, len - ETH_FCS_LEN);
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+
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+ /*
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+ * The bmCRC helps to denote when the CRC field in
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+ * the Ethernet frame contains a calculated CRC:
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+ * bmCRC = 1 : CRC is calculated
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+ * bmCRC = 0 : CRC = 0xDEADBEEF
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+ */
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+ if (header & BIT(14))
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+ crc2 = ~crc32_le(~0, skb2->data, len);
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+ else
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+ crc2 = 0xdeadbeef;
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+
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+ if (is_last)
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+ return crc == crc2;
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+
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+ if (unlikely(crc != crc2)) {
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+ dev->stats.rx_errors++;
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+ dev_kfree_skb_any(skb2);
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+ } else
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+ usbnet_skb_return(dev, skb2);
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+ }
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+
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+next:
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+ skb_pull(skb, len);
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+ } while (skb->len);
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+
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+ return 1;
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+}
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+
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+static const struct driver_info eem_info = {
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+ .description = "CDC EEM Device",
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+ .flags = FLAG_ETHER,
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+ .bind = eem_bind,
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+ .rx_fixup = eem_rx_fixup,
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+ .tx_fixup = eem_tx_fixup,
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+};
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+
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+/*-------------------------------------------------------------------------*/
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+
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+static const struct usb_device_id products[] = {
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+{
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+ USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_EEM,
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+ USB_CDC_PROTO_EEM),
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+ .driver_info = (unsigned long) &eem_info,
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+},
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+{
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+ /* EMPTY == end of list */
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+},
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+};
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+MODULE_DEVICE_TABLE(usb, products);
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+
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+static struct usb_driver eem_driver = {
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+ .name = "cdc_eem",
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+ .id_table = products,
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+ .probe = usbnet_probe,
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+ .disconnect = usbnet_disconnect,
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+ .suspend = usbnet_suspend,
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+ .resume = usbnet_resume,
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+};
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+
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+
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+static int __init eem_init(void)
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+{
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+ return usb_register(&eem_driver);
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+}
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+module_init(eem_init);
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+
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+static void __exit eem_exit(void)
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+{
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+ usb_deregister(&eem_driver);
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+}
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+module_exit(eem_exit);
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+
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+MODULE_AUTHOR("Omar Laazimani <omar.oberthur@gmail.com>");
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+MODULE_DESCRIPTION("USB CDC EEM");
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+MODULE_LICENSE("GPL");
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