usb ethernet gadget: split CDC Ethernet function

This is a "CDC Ethernet" (ECM) function driver, extracted from the
all-in-one Ethernet gadget driver.

This is a good example of how to implement interface altsettings.
In fact it's currently the only such example in the gadget stack,
pending addition of OBEX support.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 881 insertions, 1 deletions

diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index e9e0e61eb0ec..564065253643 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -25,7 +25,7 @@ obj-$(CONFIG_USB_M66592)	+= m66592-udc.o
 C_UTILS =       composite.o usbstring.o config.o epautoconf.o
 
 g_zero-objs                     := zero.o f_sourcesink.o f_loopback.o $(C_UTILS)
-g_ether-objs                    := ether.o u_ether.o f_subset.o $(C_UTILS)
+g_ether-objs                    := ether.o u_ether.o f_subset.o f_ecm.o $(C_UTILS)
 g_serial-objs                   := serial.o u_serial.o f_acm.o f_serial.o $(C_UTILS)
 g_midi-objs                     := gmidi.o usbstring.o config.o epautoconf.o
 gadgetfs-objs                   := inode.o
diff --git a/drivers/usb/gadget/f_ecm.c b/drivers/usb/gadget/f_ecm.c
new file mode 100644
index 000000000000..0822e9d7693a
--- /dev/null
+++ b/drivers/usb/gadget/f_ecm.c
@@ -0,0 +1,833 @@
+/*
+ * f_ecm.c -- USB CDC Ethernet (ECM) link function driver
+ *
+ * Copyright (C) 2003-2005,2008 David Brownell
+ * Copyright (C) 2008 Nokia Corporation
+ *
+ * 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 VERBOSE_DEBUG */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/etherdevice.h>
+
+#include "u_ether.h"
+
+
+/*
+ * This function is a "CDC Ethernet Networking Control Model" (CDC ECM)
+ * Ethernet link.  The data transfer model is simple (packets sent and
+ * received over bulk endpoints using normal short packet termination),
+ * and the control model exposes various data and optional notifications.
+ *
+ * ECM is well standardized and (except for Microsoft) supported by most
+ * operating systems with USB host support.  It's the preferred interop
+ * solution for Ethernet over USB, at least for firmware based solutions.
+ * (Hardware solutions tend to be more minimalist.)  A newer and simpler
+ * "Ethernet Emulation Model" (CDC EEM) hasn't yet caught on.
+ *
+ * Note that ECM requires the use of "alternate settings" for its data
+ * interface.  This means that the set_alt() method has real work to do,
+ * and also means that a get_alt() method is required.
+ */
+
+struct ecm_ep_descs {
+        struct usb_endpoint_descriptor  *in;
+        struct usb_endpoint_descriptor  *out;
+        struct usb_endpoint_descriptor  *notify;
+};
+
+enum ecm_notify_state {
+        ECM_NOTIFY_NONE,                /* don't notify */
+        ECM_NOTIFY_CONNECT,             /* issue CONNECT next */
+        ECM_NOTIFY_SPEED,               /* issue SPEED_CHANGE next */
+};
+
+struct f_ecm {
+        struct gether                   port;
+        u8                              ctrl_id, data_id;
+
+        char                            ethaddr[14];
+
+        struct usb_descriptor_header    **fs_function;
+        struct ecm_ep_descs             fs;
+        struct usb_descriptor_header    **hs_function;
+        struct ecm_ep_descs             hs;
+
+        struct usb_ep                   *notify;
+        struct usb_endpoint_descriptor  *notify_desc;
+        struct usb_request              *notify_req;
+        u8                              notify_state;
+        bool                            is_open;
+
+        /* FIXME is_open needs some irq-ish locking
+         * ... possibly the same as port.ioport
+         */
+};
+
+static inline struct f_ecm *func_to_ecm(struct usb_function *f)
+{
+        return container_of(f, struct f_ecm, port.func);
+}
+
+/* peak (theoretical) bulk transfer rate in bits-per-second */
+static inline unsigned bitrate(struct usb_gadget *g)
+{
+        if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
+                return 13 * 512 * 8 * 1000 * 8;
+        else
+                return 19 *  64 * 1 * 1000 * 8;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * Include the status endpoint if we can, even though it's optional.
+ *
+ * Use wMaxPacketSize big enough to fit CDC_NOTIFY_SPEED_CHANGE in one
+ * packet, to simplify cancellation; and a big transfer interval, to
+ * waste less bandwidth.
+ *
+ * Some drivers (like Linux 2.4 cdc-ether!) "need" it to exist even
+ * if they ignore the connect/disconnect notifications that real aether
+ * can provide.  More advanced cdc configurations might want to support
+ * encapsulated commands (vendor-specific, using control-OUT).
+ */
+
+#define LOG2_STATUS_INTERVAL_MSEC       5       /* 1 << 5 == 32 msec */
+#define STATUS_BYTECOUNT                16      /* 8 byte header + data */
+
+
+/* interface descriptor: */
+
+static struct usb_interface_descriptor ecm_control_intf __initdata = {
+        .bLength =              sizeof ecm_control_intf,
+        .bDescriptorType =      USB_DT_INTERFACE,
+
+        /* .bInterfaceNumber = DYNAMIC */
+        /* status endpoint is optional; this could be patched later */
+        .bNumEndpoints =        1,
+        .bInterfaceClass =      USB_CLASS_COMM,
+        .bInterfaceSubClass =   USB_CDC_SUBCLASS_ETHERNET,
+        .bInterfaceProtocol =   USB_CDC_PROTO_NONE,
+        /* .iInterface = DYNAMIC */
+};
+
+static struct usb_cdc_header_desc header_desc __initdata = {
+        .bLength =              sizeof header_desc,
+        .bDescriptorType =      USB_DT_CS_INTERFACE,
+        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,
+
+        .bcdCDC =               __constant_cpu_to_le16(0x0110),
+};
+
+static struct usb_cdc_union_desc ecm_union_desc __initdata = {
+        .bLength =              sizeof(ecm_union_desc),
+        .bDescriptorType =      USB_DT_CS_INTERFACE,
+        .bDescriptorSubType =   USB_CDC_UNION_TYPE,
+        /* .bMasterInterface0 = DYNAMIC */
+        /* .bSlaveInterface0 =  DYNAMIC */
+};
+
+static struct usb_cdc_ether_desc ether_desc __initdata = {
+        .bLength =              sizeof ether_desc,
+        .bDescriptorType =      USB_DT_CS_INTERFACE,
+        .bDescriptorSubType =   USB_CDC_ETHERNET_TYPE,
+
+        /* this descriptor actually adds value, surprise! */
+        /* .iMACAddress = DYNAMIC */
+        .bmEthernetStatistics = __constant_cpu_to_le32(0), /* no statistics */
+        .wMaxSegmentSize =      __constant_cpu_to_le16(ETH_FRAME_LEN),
+        .wNumberMCFilters =     __constant_cpu_to_le16(0),
+        .bNumberPowerFilters =  0,
+};
+
+/* the default data interface has no endpoints ... */
+
+static struct usb_interface_descriptor ecm_data_nop_intf __initdata = {
+        .bLength =              sizeof ecm_data_nop_intf,
+        .bDescriptorType =      USB_DT_INTERFACE,
+
+        .bInterfaceNumber =     1,
+        .bAlternateSetting =    0,
+        .bNumEndpoints =        0,
+        .bInterfaceClass =      USB_CLASS_CDC_DATA,
+        .bInterfaceSubClass =   0,
+        .bInterfaceProtocol =   0,
+        /* .iInterface = DYNAMIC */
+};
+
+/* ... but the "real" data interface has two bulk endpoints */
+
+static struct usb_interface_descriptor ecm_data_intf __initdata = {
+        .bLength =              sizeof ecm_data_intf,
+        .bDescriptorType =      USB_DT_INTERFACE,
+
+        .bInterfaceNumber =     1,
+        .bAlternateSetting =    1,
+        .bNumEndpoints =        2,
+        .bInterfaceClass =      USB_CLASS_CDC_DATA,
+        .bInterfaceSubClass =   0,
+        .bInterfaceProtocol =   0,
+        /* .iInterface = DYNAMIC */
+};
+
+/* full speed support: */
+
+static struct usb_endpoint_descriptor fs_notify_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_IN,
+        .bmAttributes =         USB_ENDPOINT_XFER_INT,
+        .wMaxPacketSize =       __constant_cpu_to_le16(STATUS_BYTECOUNT),
+        .bInterval =            1 << LOG2_STATUS_INTERVAL_MSEC,
+};
+
+static struct usb_endpoint_descriptor fs_in_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_IN,
+        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_endpoint_descriptor fs_out_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_OUT,
+        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_descriptor_header *eth_fs_function[] __initdata = {
+        /* CDC ECM control descriptors */
+        (struct usb_descriptor_header *) &ecm_control_intf,
+        (struct usb_descriptor_header *) &header_desc,
+        (struct usb_descriptor_header *) &ecm_union_desc,
+        (struct usb_descriptor_header *) &ether_desc,
+        /* NOTE: status endpoint might need to be removed */
+        (struct usb_descriptor_header *) &fs_notify_desc,
+        /* data interface, altsettings 0 and 1 */
+        (struct usb_descriptor_header *) &ecm_data_nop_intf,
+        (struct usb_descriptor_header *) &ecm_data_intf,
+        (struct usb_descriptor_header *) &fs_in_desc,
+        (struct usb_descriptor_header *) &fs_out_desc,
+        NULL,
+};
+
+/* high speed support: */
+
+static struct usb_endpoint_descriptor hs_notify_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_IN,
+        .bmAttributes =         USB_ENDPOINT_XFER_INT,
+        .wMaxPacketSize =       __constant_cpu_to_le16(STATUS_BYTECOUNT),
+        .bInterval =            LOG2_STATUS_INTERVAL_MSEC + 4,
+};
+static struct usb_endpoint_descriptor hs_in_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_IN,
+        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
+        .wMaxPacketSize =       __constant_cpu_to_le16(512),
+};
+
+static struct usb_endpoint_descriptor hs_out_desc __initdata = {
+        .bLength =              USB_DT_ENDPOINT_SIZE,
+        .bDescriptorType =      USB_DT_ENDPOINT,
+
+        .bEndpointAddress =     USB_DIR_OUT,
+        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
+        .wMaxPacketSize =       __constant_cpu_to_le16(512),
+};
+
+static struct usb_descriptor_header *eth_hs_function[] __initdata = {
+        /* CDC ECM control descriptors */
+        (struct usb_descriptor_header *) &ecm_control_intf,
+        (struct usb_descriptor_header *) &header_desc,
+        (struct usb_descriptor_header *) &ecm_union_desc,
+        (struct usb_descriptor_header *) &ether_desc,
+        /* NOTE: status endpoint might need to be removed */
+        (struct usb_descriptor_header *) &hs_notify_desc,
+        /* data interface, altsettings 0 and 1 */
+        (struct usb_descriptor_header *) &ecm_data_nop_intf,
+        (struct usb_descriptor_header *) &ecm_data_intf,
+        (struct usb_descriptor_header *) &hs_in_desc,
+        (struct usb_descriptor_header *) &hs_out_desc,
+        NULL,
+};
+
+/* string descriptors: */
+
+static struct usb_string ecm_string_defs[] = {
+        [0].s = "CDC Ethernet Control Model (ECM)",
+        [1].s = NULL /* DYNAMIC */,
+        [2].s = "CDC Ethernet Data",
+        {  } /* end of list */
+};
+
+static struct usb_gadget_strings ecm_string_table = {
+        .language =             0x0409, /* en-us */
+        .strings =              ecm_string_defs,
+};
+
+static struct usb_gadget_strings *ecm_strings[] = {
+        &ecm_string_table,
+        NULL,
+};
+
+/*-------------------------------------------------------------------------*/
+
+static void ecm_do_notify(struct f_ecm *ecm)
+{
+        struct usb_request              *req = ecm->notify_req;
+        struct usb_cdc_notification     *event;
+        struct usb_composite_dev        *cdev = ecm->port.func.config->cdev;
+        __le32                          *data;
+        int                             status;
+
+        /* notification already in flight? */
+        if (!req)
+                return;
+
+        event = req->buf;
+        switch (ecm->notify_state) {
+        case ECM_NOTIFY_NONE:
+                return;
+
+        case ECM_NOTIFY_CONNECT:
+                event->bNotificationType = USB_CDC_NOTIFY_NETWORK_CONNECTION;
+                if (ecm->is_open)
+                        event->wValue = cpu_to_le16(1);
+                else
+                        event->wValue = cpu_to_le16(0);
+                event->wLength = 0;
+                req->length = sizeof *event;
+
+                DBG(cdev, "notify connect %s\n",
+                                ecm->is_open ? "true" : "false");
+                ecm->notify_state = ECM_NOTIFY_SPEED;
+                break;
+
+        case ECM_NOTIFY_SPEED:
+                event->bNotificationType = USB_CDC_NOTIFY_SPEED_CHANGE;
+                event->wValue = cpu_to_le16(0);
+                event->wLength = cpu_to_le16(8);
+                req->length = STATUS_BYTECOUNT;
+
+                /* SPEED_CHANGE data is up/down speeds in bits/sec */
+                data = req->buf + sizeof *event;
+                data[0] = cpu_to_le32(bitrate(cdev->gadget));
+                data[1] = data[0];
+
+                DBG(cdev, "notify speed %d\n", bitrate(cdev->gadget));
+                ecm->notify_state = ECM_NOTIFY_NONE;
+                break;
+        }
+        event->bmRequestType = 0xA1;
+        event->wIndex = cpu_to_le16(ecm->ctrl_id);
+
+        ecm->notify_req = NULL;
+        status = usb_ep_queue(ecm->notify, req, GFP_ATOMIC);
+        if (status < 0) {
+                ecm->notify_req = req;
+                DBG(cdev, "notify --> %d\n", status);
+        }
+}
+
+static void ecm_notify(struct f_ecm *ecm)
+{
+        /* NOTE on most versions of Linux, host side cdc-ethernet
+         * won't listen for notifications until its netdevice opens.
+         * The first notification then sits in the FIFO for a long
+         * time, and the second one is queued.
+         */
+        ecm->notify_state = ECM_NOTIFY_CONNECT;
+        ecm_do_notify(ecm);
+}
+
+static void ecm_notify_complete(struct usb_ep *ep, struct usb_request *req)
+{
+        struct f_ecm                    *ecm = req->context;
+        struct usb_composite_dev        *cdev = ecm->port.func.config->cdev;
+        struct usb_cdc_notification     *event = req->buf;
+
+        switch (req->status) {
+        case 0:
+                /* no fault */
+                break;
+        case -ECONNRESET:
+        case -ESHUTDOWN:
+                ecm->notify_state = ECM_NOTIFY_NONE;
+                break;
+        default:
+                DBG(cdev, "event %02x --> %d\n",
+                        event->bNotificationType, req->status);
+                break;
+        }
+        ecm->notify_req = req;
+        ecm_do_notify(ecm);
+}
+
+static int ecm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
+{
+        struct f_ecm            *ecm = func_to_ecm(f);
+        struct usb_composite_dev *cdev = f->config->cdev;
+        struct usb_request      *req = cdev->req;
+        int                     value = -EOPNOTSUPP;
+        u16                     w_index = le16_to_cpu(ctrl->wIndex);
+        u16                     w_value = le16_to_cpu(ctrl->wValue);
+        u16                     w_length = le16_to_cpu(ctrl->wLength);
+
+        /* composite driver infrastructure handles everything except
+         * CDC class messages; interface activation uses set_alt().
+         */
+        switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
+        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+                        | USB_CDC_SET_ETHERNET_PACKET_FILTER:
+                /* see 6.2.30: no data, wIndex = interface,
+                 * wValue = packet filter bitmap
+                 */
+                if (w_length != 0 || w_index != ecm->ctrl_id)
+                        goto invalid;
+                DBG(cdev, "packet filter %02x\n", w_value);
+                /* REVISIT locking of cdc_filter.  This assumes the UDC
+                 * driver won't have a concurrent packet TX irq running on
+                 * another CPU; or that if it does, this write is atomic...
+                 */
+                ecm->port.cdc_filter = w_value;
+                value = 0;
+                break;
+
+        /* and optionally:
+         * case USB_CDC_SEND_ENCAPSULATED_COMMAND:
+         * case USB_CDC_GET_ENCAPSULATED_RESPONSE:
+         * case USB_CDC_SET_ETHERNET_MULTICAST_FILTERS:
+         * case USB_CDC_SET_ETHERNET_PM_PATTERN_FILTER:
+         * case USB_CDC_GET_ETHERNET_PM_PATTERN_FILTER:
+         * case USB_CDC_GET_ETHERNET_STATISTIC:
+         */
+
+        default:
+invalid:
+                DBG(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
+                        ctrl->bRequestType, ctrl->bRequest,
+                        w_value, w_index, w_length);
+        }
+
+        /* respond with data transfer or status phase? */
+        if (value >= 0) {
+                DBG(cdev, "ecm req%02x.%02x v%04x i%04x l%d\n",
+                        ctrl->bRequestType, ctrl->bRequest,
+                        w_value, w_index, w_length);
+                req->zero = 0;
+                req->length = value;
+                value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
+                if (value < 0)
+                        ERROR(cdev, "ecm req %02x.%02x response err %d\n",
+                                        ctrl->bRequestType, ctrl->bRequest,
+                                        value);
+        }
+
+        /* device either stalls (value < 0) or reports success */
+        return value;
+}
+
+
+static int ecm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+        struct f_ecm            *ecm = func_to_ecm(f);
+        struct usb_composite_dev *cdev = f->config->cdev;
+
+        /* Control interface has only altsetting 0 */
+        if (intf == ecm->ctrl_id) {
+                if (alt != 0)
+                        goto fail;
+
+                if (ecm->notify->driver_data) {
+                        VDBG(cdev, "reset ecm control %d\n", intf);
+                        usb_ep_disable(ecm->notify);
+                } else {
+                        VDBG(cdev, "init ecm ctrl %d\n", intf);
+                        ecm->notify_desc = ep_choose(cdev->gadget,
+                                        ecm->hs.notify,
+                                        ecm->fs.notify);
+                }
+                usb_ep_enable(ecm->notify, ecm->notify_desc);
+                ecm->notify->driver_data = ecm;
+
+        /* Data interface has two altsettings, 0 and 1 */
+        } else if (intf == ecm->data_id) {
+                if (alt > 1)
+                        goto fail;
+
+                if (ecm->port.in_ep->driver_data) {
+                        DBG(cdev, "reset ecm\n");
+                        gether_disconnect(&ecm->port);
+                }
+
+                if (!ecm->port.in) {
+                        DBG(cdev, "init ecm\n");
+                        ecm->port.in = ep_choose(cdev->gadget,
+                                        ecm->hs.in, ecm->fs.in);
+                        ecm->port.out = ep_choose(cdev->gadget,
+                                        ecm->hs.out, ecm->fs.out);
+                }
+
+                /* CDC Ethernet only sends data in non-default altsettings.
+                 * Changing altsettings resets filters, statistics, etc.
+                 */
+                if (alt == 1) {
+                        struct net_device       *net;
+
+                        /* Enable zlps by default for ECM conformance;
+                         * override for musb_hdrc (avoids txdma ovhead)
+                         * and sa1100 (can't).
+                         */
+                        ecm->port.is_zlp_ok = !(
+                                   gadget_is_sa1100(cdev->gadget)
+                                || gadget_is_musbhdrc(cdev->gadget)
+                                );
+                        ecm->port.cdc_filter = DEFAULT_FILTER;
+                        DBG(cdev, "activate ecm\n");
+                        net = gether_connect(&ecm->port);
+                        if (IS_ERR(net))
+                                return PTR_ERR(net);
+                }
+
+                /* NOTE this can be a minor disagreement with the ECM spec,
+                 * which says speed notifications will "always" follow
+                 * connection notifications.  But we allow one connect to
+                 * follow another (if the first is in flight), and instead
+                 * just guarantee that a speed notification is always sent.
+                 */
+                ecm_notify(ecm);
+        } else
+                goto fail;
+
+        return 0;
+fail:
+        return -EINVAL;
+}
+
+/* Because the data interface supports multiple altsettings,
+ * this ECM function *MUST* implement a get_alt() method.
+ */
+static int ecm_get_alt(struct usb_function *f, unsigned intf)
+{
+        struct f_ecm            *ecm = func_to_ecm(f);
+
+        if (intf == ecm->ctrl_id)
+                return 0;
+        return ecm->port.in_ep->driver_data ? 1 : 0;
+}
+
+static void ecm_disable(struct usb_function *f)
+{
+        struct f_ecm            *ecm = func_to_ecm(f);
+        struct usb_composite_dev *cdev = f->config->cdev;
+
+        DBG(cdev, "ecm deactivated\n");
+
+        if (ecm->port.in_ep->driver_data)
+                gether_disconnect(&ecm->port);
+
+        if (ecm->notify->driver_data) {
+                usb_ep_disable(ecm->notify);
+                ecm->notify->driver_data = NULL;
+                ecm->notify_desc = NULL;
+        }
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * Callbacks let us notify the host about connect/disconnect when the
+ * net device is opened or closed.
+ *
+ * For testing, note that link states on this side include both opened
+ * and closed variants of:
+ *
+ *   - disconnected/unconfigured
+ *   - configured but inactive (data alt 0)
+ *   - configured and active (data alt 1)
+ *
+ * Each needs to be tested with unplug, rmmod, SET_CONFIGURATION, and
+ * SET_INTERFACE (altsetting).  Remember also that "configured" doesn't
+ * imply the host is actually polling the notification endpoint, and
+ * likewise that "active" doesn't imply it's actually using the data
+ * endpoints for traffic.
+ */
+
+static void ecm_open(struct gether *geth)
+{
+        struct f_ecm            *ecm = func_to_ecm(&geth->func);
+
+        DBG(ecm->port.func.config->cdev, "%s\n", __func__);
+
+        ecm->is_open = true;
+        ecm_notify(ecm);
+}
+
+static void ecm_close(struct gether *geth)
+{
+        struct f_ecm            *ecm = func_to_ecm(&geth->func);
+
+        DBG(ecm->port.func.config->cdev, "%s\n", __func__);
+
+        ecm->is_open = false;
+        ecm_notify(ecm);
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* ethernet function driver setup/binding */
+
+static int __init
+ecm_bind(struct usb_configuration *c, struct usb_function *f)
+{
+        struct usb_composite_dev *cdev = c->cdev;
+        struct f_ecm            *ecm = func_to_ecm(f);
+        int                     status;
+        struct usb_ep           *ep;
+
+        /* allocate instance-specific interface IDs */
+        status = usb_interface_id(c, f);
+        if (status < 0)
+                goto fail;
+        ecm->ctrl_id = status;
+
+        ecm_control_intf.bInterfaceNumber = status;
+        ecm_union_desc.bMasterInterface0 = status;
+
+        status = usb_interface_id(c, f);
+        if (status < 0)
+                goto fail;
+        ecm->data_id = status;
+
+        ecm_data_nop_intf.bInterfaceNumber = status;
+        ecm_data_intf.bInterfaceNumber = status;
+        ecm_union_desc.bSlaveInterface0 = status;
+
+        status = -ENODEV;
+
+        /* allocate instance-specific endpoints */
+        ep = usb_ep_autoconfig(cdev->gadget, &fs_in_desc);
+        if (!ep)
+                goto fail;
+        ecm->port.in_ep = ep;
+        ep->driver_data = cdev; /* claim */
+
+        ep = usb_ep_autoconfig(cdev->gadget, &fs_out_desc);
+        if (!ep)
+                goto fail;
+        ecm->port.out_ep = ep;
+        ep->driver_data = cdev; /* claim */
+
+        /* NOTE:  a status/notification endpoint is *OPTIONAL* but we
+         * don't treat it that way.  It's simpler, and some newer CDC
+         * profiles (wireless handsets) no longer treat it as optional.
+         */
+        ep = usb_ep_autoconfig(cdev->gadget, &fs_notify_desc);
+        if (!ep)
+                goto fail;
+        ecm->notify = ep;
+        ep->driver_data = cdev; /* claim */
+
+        status = -ENOMEM;
+
+        /* allocate notification request and buffer */
+        ecm->notify_req = usb_ep_alloc_request(ep, GFP_KERNEL);
+        if (!ecm->notify_req)
+                goto fail;
+        ecm->notify_req->buf = kmalloc(STATUS_BYTECOUNT, GFP_KERNEL);
+        if (!ecm->notify_req->buf)
+                goto fail;
+        ecm->notify_req->context = ecm;
+        ecm->notify_req->complete = ecm_notify_complete;
+
+        /* copy descriptors, and track endpoint copies */
+        f->descriptors = usb_copy_descriptors(eth_fs_function);
+        if (!f->descriptors)
+                goto fail;
+
+        ecm->fs.in = usb_find_endpoint(eth_fs_function,
+                        f->descriptors, &fs_in_desc);
+        ecm->fs.out = usb_find_endpoint(eth_fs_function,
+                        f->descriptors, &fs_out_desc);
+        ecm->fs.notify = usb_find_endpoint(eth_fs_function,
+                        f->descriptors, &fs_notify_desc);
+
+        /* support all relevant hardware speeds... we expect that when
+         * hardware is dual speed, all bulk-capable endpoints work at
+         * both speeds
+         */
+        if (gadget_is_dualspeed(c->cdev->gadget)) {
+                hs_in_desc.bEndpointAddress =
+                                fs_in_desc.bEndpointAddress;
+                hs_out_desc.bEndpointAddress =
+                                fs_out_desc.bEndpointAddress;
+                hs_notify_desc.bEndpointAddress =
+                                fs_notify_desc.bEndpointAddress;
+
+                /* copy descriptors, and track endpoint copies */
+                f->hs_descriptors = usb_copy_descriptors(eth_hs_function);
+                if (!f->hs_descriptors)
+                        goto fail;
+
+                ecm->hs.in = usb_find_endpoint(eth_hs_function,
+                                f->hs_descriptors, &hs_in_desc);
+                ecm->hs.out = usb_find_endpoint(eth_hs_function,
+                                f->hs_descriptors, &hs_out_desc);
+                ecm->hs.notify = usb_find_endpoint(eth_hs_function,
+                                f->hs_descriptors, &hs_notify_desc);
+        }
+
+        /* NOTE:  all that is done without knowing or caring about
+         * the network link ... which is unavailable to this code
+         * until we're activated via set_alt().
+         */
+
+        ecm->port.open = ecm_open;
+        ecm->port.close = ecm_close;
+
+        DBG(cdev, "CDC Ethernet: %s speed IN/%s OUT/%s NOTIFY/%s\n",
+                        gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
+                        ecm->port.in_ep->name, ecm->port.out_ep->name,
+                        ecm->notify->name);
+        return 0;
+
+fail:
+        if (f->descriptors)
+                usb_free_descriptors(f->descriptors);
+
+        if (ecm->notify_req) {
+                kfree(ecm->notify_req->buf);
+                usb_ep_free_request(ecm->notify, ecm->notify_req);
+        }
+
+        /* we might as well release our claims on endpoints */
+        if (ecm->notify)
+                ecm->notify->driver_data = NULL;
+        if (ecm->port.out)
+                ecm->port.out_ep->driver_data = NULL;
+        if (ecm->port.in)
+                ecm->port.in_ep->driver_data = NULL;
+
+        ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
+
+        return status;
+}
+
+static void
+ecm_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+        struct f_ecm            *ecm = func_to_ecm(f);
+
+        DBG(c->cdev, "ecm unbind\n");
+
+        if (gadget_is_dualspeed(c->cdev->gadget))
+                usb_free_descriptors(f->hs_descriptors);
+        usb_free_descriptors(f->descriptors);
+
+        kfree(ecm->notify_req->buf);
+        usb_ep_free_request(ecm->notify, ecm->notify_req);
+
+        ecm_string_defs[1].s = NULL;
+        kfree(ecm);
+}
+
+/**
+ * ecm_bind_config - add CDC Ethernet network link to a configuration
+ * @c: the configuration to support the network link
+ * @ethaddr: a buffer in which the ethernet address of the host side
+ *      side of the link was recorded
+ * Context: single threaded during gadget setup
+ *
+ * Returns zero on success, else negative errno.
+ *
+ * Caller must have called @gether_setup().  Caller is also responsible
+ * for calling @gether_cleanup() before module unload.
+ */
+int __init ecm_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN])
+{
+        struct f_ecm    *ecm;
+        int             status;
+
+        if (!can_support_ecm(c->cdev->gadget) || !ethaddr)
+                return -EINVAL;
+
+        /* maybe allocate device-global string IDs */
+        if (ecm_string_defs[0].id == 0) {
+
+                /* control interface label */
+                status = usb_string_id(c->cdev);
+                if (status < 0)
+                        return status;
+                ecm_string_defs[0].id = status;
+                ecm_control_intf.iInterface = status;
+
+                /* data interface label */
+                status = usb_string_id(c->cdev);
+                if (status < 0)
+                        return status;
+                ecm_string_defs[2].id = status;
+                ecm_data_intf.iInterface = status;
+
+                /* MAC address */
+                status = usb_string_id(c->cdev);
+                if (status < 0)
+                        return status;
+                ecm_string_defs[1].id = status;
+                ether_desc.iMACAddress = status;
+        }
+
+        /* allocate and initialize one new instance */
+        ecm = kzalloc(sizeof *ecm, GFP_KERNEL);
+        if (!ecm)
+                return -ENOMEM;
+
+        /* export host's Ethernet address in CDC format */
+        snprintf(ecm->ethaddr, sizeof ecm->ethaddr,
+                "%02X%02X%02X%02X%02X%02X",
+                ethaddr[0], ethaddr[1], ethaddr[2],
+                ethaddr[3], ethaddr[4], ethaddr[5]);
+        ecm_string_defs[1].s = ecm->ethaddr;
+
+        ecm->port.cdc_filter = DEFAULT_FILTER;
+
+        ecm->port.func.name = "cdc_ethernet";
+        ecm->port.func.strings = ecm_strings;
+        /* descriptors are per-instance copies */
+        ecm->port.func.bind = ecm_bind;
+        ecm->port.func.unbind = ecm_unbind;
+        ecm->port.func.set_alt = ecm_set_alt;
+        ecm->port.func.get_alt = ecm_get_alt;
+        ecm->port.func.setup = ecm_setup;
+        ecm->port.func.disable = ecm_disable;
+
+        status = usb_add_function(c, &ecm->port.func);
+        if (status) {
+                ecm_string_defs[1].s = NULL;
+                kfree(ecm);
+        }
+        return status;
+}
diff --git a/drivers/usb/gadget/gadget_chips.h b/drivers/usb/gadget/gadget_chips.h
index ca5149ea7312..5246e8fef2b2 100644
--- a/drivers/usb/gadget/gadget_chips.h
+++ b/drivers/usb/gadget/gadget_chips.h
@@ -214,3 +214,26 @@ static inline int usb_gadget_controller_number(struct usb_gadget *gadget)
                 return 0x21;
         return -ENOENT;
 }
+
+
+/**
+ * gadget_supports_altsettings - return true if altsettings work
+ * @gadget: the gadget in question
+ */
+static inline bool gadget_supports_altsettings(struct usb_gadget *gadget)
+{
+        /* PXA 21x/25x/26x has no altsettings at all */
+        if (gadget_is_pxa(gadget))
+                return false;
+
+        /* PXA 27x and 3xx have *broken* altsetting support */
+        if (gadget_is_pxa27x(gadget))
+                return false;
+
+        /* SH3 hardware just doesn't do altsettings */
+        if (gadget_is_sh(gadget))
+                return false;
+
+        /* Everything else is *presumably* fine ... */
+        return true;
+}
diff --git a/drivers/usb/gadget/u_ether.h b/drivers/usb/gadget/u_ether.h
index 0ef823447f28..8abf197ab402 100644
--- a/drivers/usb/gadget/u_ether.h
+++ b/drivers/usb/gadget/u_ether.h
@@ -28,6 +28,9 @@
 #include <linux/usb/composite.h>
 #include <linux/usb/cdc.h>
 
+#include "gadget_chips.h"
+
+
 /*
  * This represents the USB side of an "ethernet" link, managed by a USB
  * function which provides control and (maybe) framing.  Two functions
@@ -80,7 +83,28 @@ void gether_cleanup(void);
 struct net_device *gether_connect(struct gether *);
 void gether_disconnect(struct gether *);
 
+/* Some controllers can't support CDC Ethernet (ECM) ... */
+static inline bool can_support_ecm(struct usb_gadget *gadget)
+{
+        if (!gadget_supports_altsettings(gadget))
+                return false;
+
+        /* SA1100 can do ECM, *without* status endpoint ... but we'll
+         * only use it in non-ECM mode for backwards compatibility
+         * (and since we currently require a status endpoint)
+         */
+        if (gadget_is_sa1100(gadget))
+                return false;
+
+        /* Everything else is *presumably* fine ... but this is a bit
+         * chancy, so be **CERTAIN** there are no hardware issues with
+         * your controller.  Add it above if it can't handle CDC.
+         */
+        return true;
+}
+
 /* each configuration may bind one instance of an ethernet link */
 int geth_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN]);
+int ecm_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN]);
 
 #endif /* __U_ETHER_H */