usbnet: CDC EEM support (v5)

This introduces a CDC Ethernet Emulation Model (EEM) host side
driver to support USB EEM devices.

EEM is different from the Ethernet Control Model (ECM) currently
supported by the "CDC Ethernet" driver.  One key difference is
that it doesn't require of USB interface alternate settings to
manage interface state; some maldesigned hardware can't handle
that part of USB.  It also avoids a separate USB interface for
control and status updates.

[ dbrownell@users.sourceforge.net: fix skb leaks, add rx packet
checks, improve fault handling, EEM conformance updates, cleanup ]

Signed-off-by: Omar Laazimani <omar.oberthur@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 381 insertions, 0 deletions

diff --git a/drivers/net/usb/cdc_eem.c b/drivers/net/usb/cdc_eem.c
new file mode 100644
index 000000000000..80e01778dd3b
--- /dev/null
+++ b/drivers/net/usb/cdc_eem.c
@@ -0,0 +1,381 @@
+/*
+ * USB CDC EEM network interface driver
+ * Copyright (C) 2009 Oberthur Technologies
+ * by Omar Laazimani, Olivier Condemine
+ *
+ * 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
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/ctype.h>
+#include <linux/ethtool.h>
+#include <linux/workqueue.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/crc32.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+
+
+/*
+ * This driver is an implementation of the CDC "Ethernet Emulation
+ * Model" (EEM) specification, which encapsulates Ethernet frames
+ * for transport over USB using a simpler USB device model than the
+ * previous CDC "Ethernet Control Model" (ECM, or "CDC Ethernet").
+ *
+ * For details, see www.usb.org/developers/devclass_docs/CDC_EEM10.pdf
+ *
+ * This version has been tested with GIGAntIC WuaoW SIM Smart Card on 2.6.24,
+ * 2.6.27 and 2.6.30rc2 kernel.
+ * It has also been validated on Openmoko Om 2008.12 (based on 2.6.24 kernel).
+ * build on 23-April-2009
+ */
+
+#define EEM_HEAD        2               /* 2 byte header */
+
+/*-------------------------------------------------------------------------*/
+
+static void eem_linkcmd_complete(struct urb *urb)
+{
+        dev_kfree_skb(urb->context);
+        usb_free_urb(urb);
+}
+
+static void eem_linkcmd(struct usbnet *dev, struct sk_buff *skb)
+{
+        struct urb              *urb;
+        int                     status;
+
+        urb = usb_alloc_urb(0, GFP_ATOMIC);
+        if (!urb)
+                goto fail;
+
+        usb_fill_bulk_urb(urb, dev->udev, dev->out,
+                        skb->data, skb->len, eem_linkcmd_complete, skb);
+
+        status = usb_submit_urb(urb, GFP_ATOMIC);
+        if (status) {
+                usb_free_urb(urb);
+fail:
+                dev_kfree_skb(skb);
+                devwarn(dev, "link cmd failure\n");
+                return;
+        }
+}
+
+static int eem_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+        int status = 0;
+
+        status = usbnet_get_endpoints(dev, intf);
+        if (status < 0) {
+                usb_set_intfdata(intf, NULL);
+                usb_driver_release_interface(driver_of(intf), intf);
+                return status;
+        }
+
+        /* no jumbogram (16K) support for now */
+
+        dev->net->hard_header_len += EEM_HEAD + ETH_FCS_LEN;
+
+        return 0;
+}
+
+/*
+ * EEM permits packing multiple Ethernet frames into USB transfers
+ * (a "bundle"), but for TX we don't try to do that.
+ */
+static struct sk_buff *eem_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
+                                       gfp_t flags)
+{
+        struct sk_buff  *skb2 = NULL;
+        u16             len = skb->len;
+        u32             crc = 0;
+        int             padlen = 0;
+
+        /* When ((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket) is
+         * zero, stick two bytes of zero length EEM packet on the end.
+         * Else the framework would add invalid single byte padding,
+         * since it can't know whether ZLPs will be handled right by
+         * all the relevant hardware and software.
+         */
+        if (!((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket))
+                padlen += 2;
+
+        if (!skb_cloned(skb)) {
+                int     headroom = skb_headroom(skb);
+                int     tailroom = skb_tailroom(skb);
+
+                if ((tailroom >= ETH_FCS_LEN + padlen)
+                                && (headroom >= EEM_HEAD))
+                        goto done;
+
+                if ((headroom + tailroom)
+                                > (EEM_HEAD + ETH_FCS_LEN + padlen)) {
+                        skb->data = memmove(skb->head +
+                                        EEM_HEAD,
+                                        skb->data,
+                                        skb->len);
+                        skb_set_tail_pointer(skb, len);
+                        goto done;
+                }
+        }
+
+        skb2 = skb_copy_expand(skb, EEM_HEAD, ETH_FCS_LEN + padlen, flags);
+        if (!skb2)
+                return NULL;
+
+        dev_kfree_skb_any(skb);
+        skb = skb2;
+
+done:
+        /* we don't use the "no Ethernet CRC" option */
+        crc = crc32_le(~0, skb->data, skb->len);
+        crc = ~crc;
+
+        put_unaligned_le32(crc, skb_put(skb, 4));
+
+        /* EEM packet header format:
+         * b0..13:      length of ethernet frame
+         * b14:         bmCRC (1 == valid Ethernet CRC)
+         * b15:         bmType (0 == data)
+         */
+        len = skb->len;
+        put_unaligned_le16(BIT(14) | len, skb_push(skb, 2));
+
+        /* Bundle a zero length EEM packet if needed */
+        if (padlen)
+                put_unaligned_le16(0, skb_put(skb, 2));
+
+        return skb;
+}
+
+static int eem_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
+{
+        /*
+         * Our task here is to strip off framing, leaving skb with one
+         * data frame for the usbnet framework code to process.  But we
+         * may have received multiple EEM payloads, or command payloads.
+         * So we must process _everything_ as if it's a header, except
+         * maybe the last data payload
+         *
+         * REVISIT the framework needs updating so that when we consume
+         * all payloads (the last or only message was a command, or a
+         * zero length EEM packet) that is not accounted as an rx_error.
+         */
+        do {
+                struct sk_buff  *skb2 = NULL;
+                u16             header;
+                u16             len = 0;
+
+                /* incomplete EEM header? */
+                if (skb->len < EEM_HEAD)
+                        return 0;
+
+                /*
+                 * EEM packet header format:
+                 * b0..14:      EEM type dependant (Data or Command)
+                 * b15:         bmType
+                 */
+                header = get_unaligned_le16(skb->data);
+                skb_pull(skb, EEM_HEAD);
+
+                /*
+                 * The bmType bit helps to denote when EEM
+                 * packet is data or command :
+                 *      bmType = 0      : EEM data payload
+                 *      bmType = 1      : EEM (link) command
+                 */
+                if (header & BIT(15)) {
+                        u16     bmEEMCmd;
+
+                        /*
+                         * EEM (link) command packet:
+                         * b0..10:      bmEEMCmdParam
+                         * b11..13:     bmEEMCmd
+                         * b14:         bmReserved (must be 0)
+                         * b15:         1 (EEM command)
+                         */
+                        if (header & BIT(14)) {
+                                devdbg(dev, "reserved command %04x\n", header);
+                                continue;
+                        }
+
+                        bmEEMCmd = (header >> 11) & 0x7;
+                        switch (bmEEMCmd) {
+
+                        /* Responding to echo requests is mandatory. */
+                        case 0:         /* Echo command */
+                                len = header & 0x7FF;
+
+                                /* bogus command? */
+                                if (skb->len < len)
+                                        return 0;
+
+                                skb2 = skb_clone(skb, GFP_ATOMIC);
+                                if (unlikely(!skb2))
+                                        goto next;
+                                skb_trim(skb2, len);
+                                put_unaligned_le16(BIT(15) | (1 << 11) | len,
+                                                skb_push(skb2, 2));
+                                eem_linkcmd(dev, skb2);
+                                break;
+
+                        /*
+                         * Host may choose to ignore hints.
+                         *  - suspend: peripheral ready to suspend
+                         *  - response: suggest N millisec polling
+                         *  - response complete: suggest N sec polling
+                         */
+                        case 2:         /* Suspend hint */
+                        case 3:         /* Response hint */
+                        case 4:         /* Response complete hint */
+                                continue;
+
+                        /*
+                         * Hosts should never receive host-to-peripheral
+                         * or reserved command codes; or responses to an
+                         * echo command we didn't send.
+                         */
+                        case 1:         /* Echo response */
+                        case 5:         /* Tickle */
+                        default:        /* reserved */
+                                devwarn(dev, "unexpected link command %d\n",
+                                                bmEEMCmd);
+                                continue;
+                        }
+
+                } else {
+                        u32     crc, crc2;
+                        int     is_last;
+
+                        /* zero length EEM packet? */
+                        if (header == 0)
+                                continue;
+
+                        /*
+                         * EEM data packet header :
+                         * b0..13:      length of ethernet frame
+                         * b14:         bmCRC
+                         * b15:         0 (EEM data)
+                         */
+                        len = header & 0x3FFF;
+
+                        /* bogus EEM payload? */
+                        if (skb->len < len)
+                                return 0;
+
+                        /* bogus ethernet frame? */
+                        if (len < (ETH_HLEN + ETH_FCS_LEN))
+                                goto next;
+
+                        /*
+                         * Treat the last payload differently: framework
+                         * code expects our "fixup" to have stripped off
+                         * headers, so "skb" is a data packet (or error).
+                         * Else if it's not the last payload, keep "skb"
+                         * for further processing.
+                         */
+                        is_last = (len == skb->len);
+                        if (is_last)
+                                skb2 = skb;
+                        else {
+                                skb2 = skb_clone(skb, GFP_ATOMIC);
+                                if (unlikely(!skb2))
+                                        return 0;
+                        }
+
+                        crc = get_unaligned_le32(skb2->data
+                                        + len - ETH_FCS_LEN);
+                        skb_trim(skb2, len - ETH_FCS_LEN);
+
+                        /*
+                         * The bmCRC helps to denote when the CRC field in
+                         * the Ethernet frame contains a calculated CRC:
+                         *      bmCRC = 1       : CRC is calculated
+                         *      bmCRC = 0       : CRC = 0xDEADBEEF
+                         */
+                        if (header & BIT(14))
+                                crc2 = ~crc32_le(~0, skb2->data, len);
+                        else
+                                crc2 = 0xdeadbeef;
+
+                        if (is_last)
+                                return crc == crc2;
+
+                        if (unlikely(crc != crc2)) {
+                                dev->stats.rx_errors++;
+                                dev_kfree_skb_any(skb2);
+                        } else
+                                usbnet_skb_return(dev, skb2);
+                }
+
+next:
+                skb_pull(skb, len);
+        } while (skb->len);
+
+        return 1;
+}
+
+static const struct driver_info eem_info = {
+        .description =  "CDC EEM Device",
+        .flags =        FLAG_ETHER,
+        .bind =         eem_bind,
+        .rx_fixup =     eem_rx_fixup,
+        .tx_fixup =     eem_tx_fixup,
+};
+
+/*-------------------------------------------------------------------------*/
+
+static const struct usb_device_id products[] = {
+{
+        USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_EEM,
+                        USB_CDC_PROTO_EEM),
+        .driver_info = (unsigned long) &eem_info,
+},
+{
+        /* EMPTY == end of list */
+},
+};
+MODULE_DEVICE_TABLE(usb, products);
+
+static struct usb_driver eem_driver = {
+        .name =         "cdc_eem",
+        .id_table =     products,
+        .probe =        usbnet_probe,
+        .disconnect =   usbnet_disconnect,
+        .suspend =      usbnet_suspend,
+        .resume =       usbnet_resume,
+};
+
+
+static int __init eem_init(void)
+{
+        return usb_register(&eem_driver);
+}
+module_init(eem_init);
+
+static void __exit eem_exit(void)
+{
+        usb_deregister(&eem_driver);
+}
+module_exit(eem_exit);
+
+MODULE_AUTHOR("Omar Laazimani <omar.oberthur@gmail.com>");
+MODULE_DESCRIPTION("USB CDC EEM");
+MODULE_LICENSE("GPL");