usb ethernet gadget: split RNDIS function

This is a RNDIS function driver, extracted from the all-in-one
Ethernet gadget driver.

Lightly tested ... there seems to be a pre-existing problem when
talking to Windows XP SP2, not quite sure what's up with that yet.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/Makefile

@@ -35,7 +35,7 @@ g_printer-objs			:= printer.o usbstring.o config.o \
 					epautoconf.o
 
 ifeq ($(CONFIG_USB_ETH_RNDIS),y)
-	g_ether-objs		+= rndis.o
+	g_ether-objs		+= f_rndis.o rndis.o
 endif
  
 obj-$(CONFIG_USB_ZERO)		+= g_zero.o

drivers/usb/gadget/f_rndis.c

+/*
+ * f_rndis.c -- RNDIS link function driver
+ *
+ * Copyright (C) 2003-2005,2008 David Brownell
+ * Copyright (C) 2003-2004 Robert Schwebel, Benedikt Spranger
+ * 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 <asm/atomic.h>
+
+#include "u_ether.h"
+#include "rndis.h"
+
+
+/*
+ * This function is an RNDIS Ethernet port -- a Microsoft protocol that's
+ * been promoted instead of the standard CDC Ethernet.  The published RNDIS
+ * spec is ambiguous, incomplete, and needlessly complex.  Variants such as
+ * ActiveSync have even worse status in terms of specification.
+ *
+ * In short:  it's a protocol controlled by (and for) Microsoft, not for an
+ * Open ecosystem or markets.  Linux supports it *only* because Microsoft
+ * doesn't support the CDC Ethernet standard.
+ *
+ * The RNDIS data transfer model is complex, with multiple Ethernet packets
+ * per USB message, and out of band data.  The control model is built around
+ * what's essentially an "RNDIS RPC" protocol.  It's all wrapped in a CDC ACM
+ * (modem, not Ethernet) veneer, with those ACM descriptors being entirely
+ * useless (they're ignored).  RNDIS expects to be the only function in its
+ * configuration, so it's no real help if you need composite devices; and
+ * it expects to be the first configuration too.
+ *
+ * There is a single technical advantage of RNDIS over CDC Ethernet, if you
+ * discount the fluff that its RPC can be made to deliver: it doesn't need
+ * a NOP altsetting for the data interface.  That lets it work on some of the
+ * "so smart it's stupid" hardware which takes over configuration changes
+ * from the software, and adds restrictions like "no altsettings".
+ *
+ * Unfortunately MSFT's RNDIS drivers are buggy.  They hang or oops, and
+ * have all sorts of contrary-to-specification oddities that can prevent
+ * them from working sanely.  Since bugfixes (or accurate specs, letting
+ * Linux work around those bugs) are unlikely to ever come from MSFT, you
+ * may want to avoid using RNDIS on purely operational grounds.
+ *
+ * Omissions from the RNDIS 1.0 specification include:
+ *
+ *   - Power management ... references data that's scattered around lots
+ *     of other documentation, which is incorrect/incomplete there too.
+ *
+ *   - There are various undocumented protocol requirements, like the need
+ *     to send garbage in some control-OUT messages.
+ *
+ *   - MS-Windows drivers sometimes emit undocumented requests.
+ */
+
+struct rndis_ep_descs {
+	struct usb_endpoint_descriptor	*in;
+	struct usb_endpoint_descriptor	*out;
+	struct usb_endpoint_descriptor	*notify;
+};
+
+struct f_rndis {
+	struct gether			port;
+	u8				ctrl_id, data_id;
+	u8				ethaddr[ETH_ALEN];
+	int				config;
+
+	struct usb_descriptor_header	**fs_function;
+	struct rndis_ep_descs		fs;
+	struct usb_descriptor_header	**hs_function;
+	struct rndis_ep_descs		hs;
+
+	struct usb_ep			*notify;
+	struct usb_endpoint_descriptor	*notify_desc;
+	struct usb_request		*notify_req;
+	atomic_t			notify_count;
+};
+
+static inline struct f_rndis *func_to_rndis(struct usb_function *f)
+{
+	return container_of(f, struct f_rndis, port.func);
+}
+
+/* peak (theoretical) bulk transfer rate in bits-per-second */
+static unsigned int 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;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ */
+
+#define LOG2_STATUS_INTERVAL_MSEC	5	/* 1 << 5 == 32 msec */
+#define STATUS_BYTECOUNT		8	/* 8 bytes data */
+
+
+/* interface descriptor: */
+
+static struct usb_interface_descriptor rndis_control_intf __initdata = {
+	.bLength =		sizeof rndis_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_ACM,
+	.bInterfaceProtocol =   USB_CDC_ACM_PROTO_VENDOR,
+	/* .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_call_mgmt_descriptor call_mgmt_descriptor __initdata = {
+	.bLength =		sizeof call_mgmt_descriptor,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_CALL_MANAGEMENT_TYPE,
+
+	.bmCapabilities =	0x00,
+	.bDataInterface =	0x01,
+};
+
+static struct usb_cdc_acm_descriptor acm_descriptor __initdata = {
+	.bLength =		sizeof acm_descriptor,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_ACM_TYPE,
+
+	.bmCapabilities =	0x00,
+};
+
+static struct usb_cdc_union_desc rndis_union_desc __initdata = {
+	.bLength =		sizeof(rndis_union_desc),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_UNION_TYPE,
+	/* .bMasterInterface0 =	DYNAMIC */
+	/* .bSlaveInterface0 =	DYNAMIC */
+};
+
+/* the data interface has two bulk endpoints */
+
+static struct usb_interface_descriptor rndis_data_intf __initdata = {
+	.bLength =		sizeof rndis_data_intf,
+	.bDescriptorType =	USB_DT_INTERFACE,
+
+	/* .bInterfaceNumber = DYNAMIC */
+	.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 = {
+	/* control interface matches ACM, not Ethernet */
+	(struct usb_descriptor_header *) &rndis_control_intf,
+	(struct usb_descriptor_header *) &header_desc,
+	(struct usb_descriptor_header *) &call_mgmt_descriptor,
+	(struct usb_descriptor_header *) &acm_descriptor,
+	(struct usb_descriptor_header *) &rndis_union_desc,
+	(struct usb_descriptor_header *) &fs_notify_desc,
+	/* data interface has no altsetting */
+	(struct usb_descriptor_header *) &rndis_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 = {
+	/* control interface matches ACM, not Ethernet */
+	(struct usb_descriptor_header *) &rndis_control_intf,
+	(struct usb_descriptor_header *) &header_desc,
+	(struct usb_descriptor_header *) &call_mgmt_descriptor,
+	(struct usb_descriptor_header *) &acm_descriptor,
+	(struct usb_descriptor_header *) &rndis_union_desc,
+	(struct usb_descriptor_header *) &hs_notify_desc,
+	/* data interface has no altsetting */
+	(struct usb_descriptor_header *) &rndis_data_intf,
+	(struct usb_descriptor_header *) &hs_in_desc,
+	(struct usb_descriptor_header *) &hs_out_desc,
+	NULL,
+};
+
+/* string descriptors: */
+
+static struct usb_string rndis_string_defs[] = {
+	[0].s = "RNDIS Communications Control",
+	[1].s = "RNDIS Ethernet Data",
+	{  } /* end of list */
+};
+
+static struct usb_gadget_strings rndis_string_table = {
+	.language =		0x0409,	/* en-us */
+	.strings =		rndis_string_defs,
+};
+
+static struct usb_gadget_strings *rndis_strings[] = {
+	&rndis_string_table,
+	NULL,
+};
+
+/*-------------------------------------------------------------------------*/
+
+static struct sk_buff *rndis_add_header(struct sk_buff *skb)
+{
+	skb = skb_realloc_headroom(skb, sizeof(struct rndis_packet_msg_type));
+	if (skb)
+		rndis_add_hdr(skb);
+	return skb;
+}
+
+static void rndis_response_available(void *_rndis)
+{
+	struct f_rndis			*rndis = _rndis;
+	struct usb_request		*req = rndis->notify_req;
+	struct usb_composite_dev	*cdev = rndis->port.func.config->cdev;
+	__le32				*data = req->buf;
+	int				status;
+
+	if (atomic_inc_return(&rndis->notify_count))
+		return;
+
+	/* Send RNDIS RESPONSE_AVAILABLE notification; a
+	 * USB_CDC_NOTIFY_RESPONSE_AVAILABLE "should" work too
+	 *
+	 * This is the only notification defined by RNDIS.
+	 */
+	data[0] = cpu_to_le32(1);
+	data[1] = cpu_to_le32(0);
+
+	status = usb_ep_queue(rndis->notify, req, GFP_ATOMIC);
+	if (status) {
+		atomic_dec(&rndis->notify_count);
+		DBG(cdev, "notify/0 --> %d\n", status);
+	}
+}
+
+static void rndis_response_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_rndis			*rndis = req->context;
+	struct usb_composite_dev	*cdev = rndis->port.func.config->cdev;
+	int				status = req->status;
+
+	/* after TX:
+	 *  - USB_CDC_GET_ENCAPSULATED_RESPONSE (ep0/control)
+	 *  - RNDIS_RESPONSE_AVAILABLE (status/irq)
+	 */
+	switch (status) {
+	case -ECONNRESET:
+	case -ESHUTDOWN:
+		/* connection gone */
+		atomic_set(&rndis->notify_count, 0);
+		break;
+	default:
+		DBG(cdev, "RNDIS %s response error %d, %d/%d\n",
+			ep->name, status,
+			req->actual, req->length);
+		/* FALLTHROUGH */
+	case 0:
+		if (ep != rndis->notify)
+			break;
+
+		/* handle multiple pending RNDIS_RESPONSE_AVAILABLE
+		 * notifications by resending until we're done
+		 */
+		if (atomic_dec_and_test(&rndis->notify_count))
+			break;
+		status = usb_ep_queue(rndis->notify, req, GFP_ATOMIC);
+		if (status) {
+			atomic_dec(&rndis->notify_count);
+			DBG(cdev, "notify/1 --> %d\n", status);
+		}
+		break;
+	}
+}
+
+static void rndis_command_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_rndis			*rndis = req->context;
+	struct usb_composite_dev	*cdev = rndis->port.func.config->cdev;
+	int				status;
+
+	/* received RNDIS command from USB_CDC_SEND_ENCAPSULATED_COMMAND */
+//	spin_lock(&dev->lock);
+	status = rndis_msg_parser(rndis->config, (u8 *) req->buf);
+	if (status < 0)
+		ERROR(cdev, "RNDIS command error %d, %d/%d\n",
+			status, req->actual, req->length);
+//	spin_unlock(&dev->lock);
+}
+
+static int
+rndis_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
+{
+	struct f_rndis		*rndis = func_to_rndis(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) {
+
+	/* RNDIS uses the CDC command encapsulation mechanism to implement
+	 * an RPC scheme, with much getting/setting of attributes by OID.
+	 */
+	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+			| USB_CDC_SEND_ENCAPSULATED_COMMAND:
+		if (w_length > req->length || w_value
+				|| w_index != rndis->ctrl_id)
+			goto invalid;
+		/* read the request; process it later */
+		value = w_length;
+		req->complete = rndis_command_complete;
+		req->context = rndis;
+		/* later, rndis_response_available() sends a notification */
+		break;
+
+	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+			| USB_CDC_GET_ENCAPSULATED_RESPONSE:
+		if (w_value || w_index != rndis->ctrl_id)
+			goto invalid;
+		else {
+			u8 *buf;
+			u32 n;
+
+			/* return the result */
+			buf = rndis_get_next_response(rndis->config, &n);
+			if (buf) {
+				memcpy(req->buf, buf, n);
+				req->complete = rndis_response_complete;
+				rndis_free_response(rndis->config, buf);
+				value = n;
+			}
+			/* else stalls ... spec says to avoid that */
+		}
+		break;
+
+	default:
+invalid:
+		VDBG(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, "rndis 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, "rndis response on err %d\n", value);
+	}
+
+	/* device either stalls (value < 0) or reports success */
+	return value;
+}
+
+
+static int rndis_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+	struct f_rndis		*rndis = func_to_rndis(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+
+	/* we know alt == 0 */
+
+	if (intf == rndis->ctrl_id) {
+		if (rndis->notify->driver_data) {
+			VDBG(cdev, "reset rndis control %d\n", intf);
+			usb_ep_disable(rndis->notify);
+		} else {
+			VDBG(cdev, "init rndis ctrl %d\n", intf);
+			rndis->notify_desc = ep_choose(cdev->gadget,
+					rndis->hs.notify,
+					rndis->fs.notify);
+		}
+		usb_ep_enable(rndis->notify, rndis->notify_desc);
+		rndis->notify->driver_data = rndis;
+
+	} else if (intf == rndis->data_id) {
+		struct net_device	*net;
+
+		if (rndis->port.in_ep->driver_data) {
+			DBG(cdev, "reset rndis\n");
+			gether_disconnect(&rndis->port);
+		} else {
+			DBG(cdev, "init rndis\n");
+			rndis->port.in = ep_choose(cdev->gadget,
+					rndis->hs.in, rndis->fs.in);
+			rndis->port.out = ep_choose(cdev->gadget,
+					rndis->hs.out, rndis->fs.out);
+		}
+
+		/* Avoid ZLPs; they can be troublesome. */
+		rndis->port.is_zlp_ok = false;
+
+		/* RNDIS should be in the "RNDIS uninitialized" state,
+		 * either never activated or after rndis_uninit().
+		 *
+		 * We don't want data to flow here until a nonzero packet
+		 * filter is set, at which point it enters "RNDIS data
+		 * initialized" state ... but we do want the endpoints
+		 * to be activated.  It's a strange little state.
+		 *
+		 * REVISIT the RNDIS gadget code has done this wrong for a
+		 * very long time.  We need another call to the link layer
+		 * code -- gether_updown(...bool) maybe -- to do it right.
+		 */
+		rndis->port.cdc_filter = 0;
+
+		DBG(cdev, "RNDIS RX/TX early activation ... \n");
+		net = gether_connect(&rndis->port);
+		if (IS_ERR(net))
+			return PTR_ERR(net);
+
+		rndis_set_param_dev(rndis->config, net,
+				&rndis->port.cdc_filter);
+	} else
+		goto fail;
+
+	return 0;
+fail:
+	return -EINVAL;
+}
+
+static void rndis_disable(struct usb_function *f)
+{
+	struct f_rndis		*rndis = func_to_rndis(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+
+	if (!rndis->notify->driver_data)
+		return;
+
+	DBG(cdev, "rndis deactivated\n");
+
+	rndis_uninit(rndis->config);
+	gether_disconnect(&rndis->port);
+
+	usb_ep_disable(rndis->notify);
+	rndis->notify->driver_data = NULL;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * This isn't quite the same mechanism as CDC Ethernet, since the
+ * notification scheme passes less data, but the same set of link
+ * states must be tested.  A key difference is that altsettings are
+ * not used to tell whether the link should send packets or not.
+ */
+
+static void rndis_open(struct gether *geth)
+{
+	struct f_rndis		*rndis = func_to_rndis(&geth->func);
+	struct usb_composite_dev *cdev = geth->func.config->cdev;
+
+	DBG(cdev, "%s\n", __func__);
+
+	rndis_set_param_medium(rndis->config, NDIS_MEDIUM_802_3,
+				bitrate(cdev->gadget) / 100);
+	rndis_signal_connect(rndis->config);
+}
+
+static void rndis_close(struct gether *geth)
+{
+	struct f_rndis		*rndis = func_to_rndis(&geth->func);
+
+	DBG(geth->func.config->cdev, "%s\n", __func__);
+
+	rndis_set_param_medium(rndis->config, NDIS_MEDIUM_802_3, 0);
+	rndis_signal_disconnect(rndis->config);
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* ethernet function driver setup/binding */
+
+static int __init
+rndis_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	struct f_rndis		*rndis = func_to_rndis(f);
+	int			status;
+	struct usb_ep		*ep;
+
+	/* allocate instance-specific interface IDs */
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	rndis->ctrl_id = status;
+
+	rndis_control_intf.bInterfaceNumber = status;
+	rndis_union_desc.bMasterInterface0 = status;
+
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	rndis->data_id = status;
+
+	rndis_data_intf.bInterfaceNumber = status;
+	rndis_union_desc.bSlaveInterface0 = status;
+
+	status = -ENODEV;
+
+	/* allocate instance-specific endpoints */
+	ep = usb_ep_autoconfig(cdev->gadget, &fs_in_desc);
+	if (!ep)
+		goto fail;
+	rndis->port.in_ep = ep;
+	ep->driver_data = cdev;	/* claim */
+
+	ep = usb_ep_autoconfig(cdev->gadget, &fs_out_desc);
+	if (!ep)
+		goto fail;
+	rndis->port.out_ep = ep;
+	ep->driver_data = cdev;	/* claim */
+
+	/* NOTE:  a status/notification endpoint is, strictly speaking,
+	 * optional.  We don't treat it that way though!  It's simpler,
+	 * and some newer profiles don't treat it as optional.
+	 */
+	ep = usb_ep_autoconfig(cdev->gadget, &fs_notify_desc);
+	if (!ep)
+		goto fail;
+	rndis->notify = ep;
+	ep->driver_data = cdev;	/* claim */
+
+	status = -ENOMEM;
+
+	/* allocate notification request and buffer */
+	rndis->notify_req = usb_ep_alloc_request(ep, GFP_KERNEL);
+	if (!rndis->notify_req)
+		goto fail;
+	rndis->notify_req->buf = kmalloc(STATUS_BYTECOUNT, GFP_KERNEL);
+	if (!rndis->notify_req->buf)
+		goto fail;
+	rndis->notify_req->length = STATUS_BYTECOUNT;
+	rndis->notify_req->context = rndis;
+	rndis->notify_req->complete = rndis_response_complete;
+
+	/* copy descriptors, and track endpoint copies */
+	f->descriptors = usb_copy_descriptors(eth_fs_function);
+	if (!f->descriptors)
+		goto fail;
+
+	rndis->fs.in = usb_find_endpoint(eth_fs_function,
+			f->descriptors, &fs_in_desc);
+	rndis->fs.out = usb_find_endpoint(eth_fs_function,
+			f->descriptors, &fs_out_desc);
+	rndis->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;
+
+		/* copy descriptors, and track endpoint copies */
+		f->hs_descriptors = usb_copy_descriptors(eth_hs_function);
+
+		if (!f->hs_descriptors)
+			goto fail;
+
+		rndis->hs.in = usb_find_endpoint(eth_hs_function,
+				f->hs_descriptors, &hs_in_desc);
+		rndis->hs.out = usb_find_endpoint(eth_hs_function,
+				f->hs_descriptors, &hs_out_desc);
+	}
+
+	rndis->port.open = rndis_open;
+	rndis->port.close = rndis_close;
+
+	status = rndis_register(rndis_response_available, rndis);
+	if (status < 0)
+		goto fail;
+	rndis->config = status;
+
+	rndis_set_param_medium(rndis->config, NDIS_MEDIUM_802_3, 0);
+	rndis_set_host_mac(rndis->config, rndis->ethaddr);
+
+#if 0
+// FIXME
+	if (rndis_set_param_vendor(rndis->config, vendorID,
+				manufacturer))
+		goto fail0;
+#endif
+
+	/* 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().
+	 */
+
+	DBG(cdev, "RNDIS: %s speed IN/%s OUT/%s NOTIFY/%s\n",
+			gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
+			rndis->port.in_ep->name, rndis->port.out_ep->name,
+			rndis->notify->name);
+	return 0;
+
+fail:
+	if (gadget_is_dualspeed(c->cdev->gadget) && f->hs_descriptors)
+		usb_free_descriptors(f->hs_descriptors);
+	if (f->descriptors)
+		usb_free_descriptors(f->descriptors);
+
+	if (rndis->notify_req) {
+		kfree(rndis->notify_req->buf);
+		usb_ep_free_request(rndis->notify, rndis->notify_req);
+	}
+
+	/* we might as well release our claims on endpoints */
+	if (rndis->notify)
+		rndis->notify->driver_data = NULL;
+	if (rndis->port.out)
+		rndis->port.out_ep->driver_data = NULL;
+	if (rndis->port.in)
+		rndis->port.in_ep->driver_data = NULL;
+
+	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
+
+	return status;
+}
+
+static void
+rndis_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct f_rndis		*rndis = func_to_rndis(f);
+
+	rndis_deregister(rndis->config);
+	rndis_exit();
+
+	if (gadget_is_dualspeed(c->cdev->gadget))
+		usb_free_descriptors(f->hs_descriptors);
+	usb_free_descriptors(f->descriptors);
+
+	kfree(rndis->notify_req->buf);
+	usb_ep_free_request(rndis->notify, rndis->notify_req);
+
+	kfree(rndis);
+}
+
+/* Some controllers can't support RNDIS ... */
+static inline bool can_support_rndis(struct usb_configuration *c)
+{
+	/* only two endpoints on sa1100 */
+	if (gadget_is_sa1100(c->cdev->gadget))
+		return false;
+
+	/* everything else is *presumably* fine */
+	return true;
+}
+
+/**
+ * rndis_bind_config - add RNDIS 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 rndis_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN])
+{
+	struct f_rndis	*rndis;
+	int		status;
+
+	if (!can_support_rndis(c) || !ethaddr)
+		return -EINVAL;
+
+	/* maybe allocate device-global string IDs */
+	if (rndis_string_defs[0].id == 0) {
+
+		/* ... and setup RNDIS itself */
+		status = rndis_init();
+		if (status < 0)
+			return status;
+
+		/* control interface label */
+		status = usb_string_id(c->cdev);
+		if (status < 0)
+			return status;
+		rndis_string_defs[0].id = status;
+		rndis_control_intf.iInterface = status;
+
+		/* data interface label */
+		status = usb_string_id(c->cdev);
+		if (status < 0)
+			return status;
+		rndis_string_defs[1].id = status;
+		rndis_data_intf.iInterface = status;
+	}
+
+	/* allocate and initialize one new instance */
+	status = -ENOMEM;
+	rndis = kzalloc(sizeof *rndis, GFP_KERNEL);
+	if (!rndis)
+		goto fail;
+
+	memcpy(rndis->ethaddr, ethaddr, ETH_ALEN);
+
+	/* RNDIS activates when the host changes this filter */
+	rndis->port.cdc_filter = 0;
+
+	/* RNDIS has special (and complex) framing */
+	rndis->port.header_len = sizeof(struct rndis_packet_msg_type);
+	rndis->port.wrap = rndis_add_header;
+	rndis->port.unwrap = rndis_rm_hdr;
+
+	rndis->port.func.name = "rndis";
+	rndis->port.func.strings = rndis_strings;
+	/* descriptors are per-instance copies */
+	rndis->port.func.bind = rndis_bind;
+	rndis->port.func.unbind = rndis_unbind;
+	rndis->port.func.set_alt = rndis_set_alt;
+	rndis->port.func.setup = rndis_setup;
+	rndis->port.func.disable = rndis_disable;
+
+	status = usb_add_function(c, &rndis->port.func);
+	if (status) {
+		kfree(rndis);
+fail:
+		rndis_exit();
+	}
+	return status;
+}

drivers/usb/gadget/u_ether.h

@@ -34,10 +34,13 @@
 /*
  * This represents the USB side of an "ethernet" link, managed by a USB
  * function which provides control and (maybe) framing.  Two functions
- * in different configurations could share the same ethernet link/netdev.
+ * in different configurations could share the same ethernet link/netdev,
+ * using different host interaction models.
  *
- * There is currently a limitation that one instance of this function
- * may be present in any given configuration.
+ * There is a current limitation that only one instance of this link may
+ * be present in any given configuration.  When that's a problem, network
+ * layer facilities can be used to package multiple logical links on this
+ * single "physical" one.
  */
 struct gether {
 	struct usb_function		func;
@@ -107,4 +110,18 @@ static inline bool can_support_ecm(struct usb_gadget *gadget)
 int geth_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN]);
 int ecm_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN]);
 
+#ifdef CONFIG_USB_ETH_RNDIS
+
+int rndis_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN]);
+
+#else
+
+static inline int
+rndis_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN])
+{
+	return 0;
+}
+
+#endif
+
 #endif /* __U_ETHER_H */