USB: gadget: Add EEM gadget driver

This patch adds a CDC EEM ethernet gadget driver.  CDC EEM is a newer
USB ethernet specification that uses a simpler interface than the older
CDC ECM.  This makes CDC EEM usable by a wider set of USB hardware.
By default the ethernet gadget will still use CDC ECM/Subset, but kernel
configuration and/or a module parameter will allow alternative use of
the CDC EEM protocol.

Changes since last version:
	- Brought in missing RNDIS changes that caused compile error
	- Modified 'sentinel CRC' checking to match EEM host driver
Signed-off-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/Kconfig

@@ -628,8 +628,8 @@ config USB_ETH
 	tristate "Ethernet Gadget (with CDC Ethernet support)"
 	depends on NET
 	help
-	  This driver implements Ethernet style communication, in either
-	  of two ways:
+	  This driver implements Ethernet style communication, in one of
+	  several ways:
 	  
 	   - The "Communication Device Class" (CDC) Ethernet Control Model.
 	     That protocol is often avoided with pure Ethernet adapters, in
@@ -639,7 +639,11 @@ config USB_ETH
 	   - On hardware can't implement that protocol, a simple CDC subset
 	     is used, placing fewer demands on USB.
 
-	  RNDIS support is a third option, more demanding than that subset.
+	   - CDC Ethernet Emulation Model (EEM) is a newer standard that has
+	     a simpler interface that can be used by more USB hardware.
+
+	  RNDIS support is an additional option, more demanding than than
+	  subset.
 
 	  Within the USB device, this gadget driver exposes a network device
 	  "usbX", where X depends on what other networking devices you have.
@@ -672,6 +676,22 @@ config USB_ETH_RNDIS
 	   XP, you'll need to download drivers from Microsoft's website; a URL
 	   is given in comments found in that info file.
 
+config USB_ETH_EEM
+       bool "Ethernet Emulation Model (EEM) support"
+       depends on USB_ETH
+       default n
+       help
+         CDC EEM is a newer USB standard that is somewhat simpler than CDC ECM
+         and therefore can be supported by more hardware.  Technically ECM and
+         EEM are designed for different applications.  The ECM model extends
+         the network interface to the target (e.g. a USB cable modem), and the
+         EEM model is for mobile devices to communicate with hosts using
+         ethernet over USB.  For Linux gadgets, however, the interface with
+         the host is the same (a usbX device), so the differences are minimal.
+
+         If you say "y" here, the Ethernet gadget driver will use the EEM
+         protocol rather than ECM.  If unsure, say "n".
+
 config USB_GADGETFS
 	tristate "Gadget Filesystem (EXPERIMENTAL)"
 	depends on EXPERIMENTAL

drivers/usb/gadget/ether.c

@@ -61,6 +61,11 @@
  * simpler, Microsoft pushes their own approach: RNDIS.  The published
  * RNDIS specs are ambiguous and appear to be incomplete, and are also
  * needlessly complex.  They borrow more from CDC ACM than CDC ECM.
+ *
+ * While CDC ECM, CDC Subset, and RNDIS are designed to extend the ethernet
+ * interface to the target, CDC EEM was designed to use ethernet over the USB
+ * link between the host and target.  CDC EEM is implemented as an alternative
+ * to those other protocols when that communication model is more appropriate
  */
 
 #define DRIVER_DESC		"Ethernet Gadget"
@@ -114,6 +119,7 @@ static inline bool has_rndis(void)
 #include "f_rndis.c"
 #include "rndis.c"
 #endif
+#include "f_eem.c"
 #include "u_ether.c"
 
 /*-------------------------------------------------------------------------*/
@@ -150,6 +156,10 @@ static inline bool has_rndis(void)
 #define RNDIS_VENDOR_NUM	0x0525	/* NetChip */
 #define RNDIS_PRODUCT_NUM	0xa4a2	/* Ethernet/RNDIS Gadget */
 
+/* For EEM gadgets */
+#define EEM_VENDOR_NUM	0x0525	/* INVALID - NEEDS TO BE ALLOCATED */
+#define EEM_PRODUCT_NUM	0xa4a1	/* INVALID - NEEDS TO BE ALLOCATED */
+
 /*-------------------------------------------------------------------------*/
 
 static struct usb_device_descriptor device_desc = {
@@ -246,8 +256,16 @@ static struct usb_configuration rndis_config_driver = {
 
 /*-------------------------------------------------------------------------*/
 
+#ifdef CONFIG_USB_ETH_EEM
+static int use_eem = 1;
+#else
+static int use_eem;
+#endif
+module_param(use_eem, bool, 0);
+MODULE_PARM_DESC(use_eem, "use CDC EEM mode");
+
 /*
- * We _always_ have an ECM or CDC Subset configuration.
+ * We _always_ have an ECM, CDC Subset, or EEM configuration.
  */
 static int __init eth_do_config(struct usb_configuration *c)
 {
@@ -258,7 +276,9 @@ static int __init eth_do_config(struct usb_configuration *c)
 		c->bmAttributes |= USB_CONFIG_ATT_WAKEUP;
 	}
 
-	if (can_support_ecm(c->cdev->gadget))
+	if (use_eem)
+		return eem_bind_config(c);
+	else if (can_support_ecm(c->cdev->gadget))
 		return ecm_bind_config(c, hostaddr);
 	else
 		return geth_bind_config(c, hostaddr);
@@ -286,7 +306,12 @@ static int __init eth_bind(struct usb_composite_dev *cdev)
 		return status;
 
 	/* set up main config label and device descriptor */
-	if (can_support_ecm(cdev->gadget)) {
+	if (use_eem) {
+		/* EEM */
+		eth_config_driver.label = "CDC Ethernet (EEM)";
+		device_desc.idVendor = cpu_to_le16(EEM_VENDOR_NUM);
+		device_desc.idProduct = cpu_to_le16(EEM_PRODUCT_NUM);
+	} else if (can_support_ecm(cdev->gadget)) {
 		/* ECM */
 		eth_config_driver.label = "CDC Ethernet (ECM)";
 	} else {

drivers/usb/gadget/f_rndis.c

@@ -286,12 +286,17 @@ static struct usb_gadget_strings *rndis_strings[] = {
 
 /*-------------------------------------------------------------------------*/
 
-static struct sk_buff *rndis_add_header(struct sk_buff *skb)
+static struct sk_buff *rndis_add_header(struct gether *port,
+					struct sk_buff *skb)
 {
-	skb = skb_realloc_headroom(skb, sizeof(struct rndis_packet_msg_type));
-	if (skb)
-		rndis_add_hdr(skb);
-	return skb;
+	struct sk_buff *skb2;
+
+	skb2 = skb_realloc_headroom(skb, sizeof(struct rndis_packet_msg_type));
+	if (skb2)
+		rndis_add_hdr(skb2);
+
+	dev_kfree_skb_any(skb);
+	return skb2;
 }
 
 static void rndis_response_available(void *_rndis)

drivers/usb/gadget/rndis.c

@@ -1022,22 +1022,29 @@ static rndis_resp_t *rndis_add_response (int configNr, u32 length)
 	return r;
 }
 
-int rndis_rm_hdr(struct sk_buff *skb)
+int rndis_rm_hdr(struct gether *port,
+			struct sk_buff *skb,
+			struct sk_buff_head *list)
 {
 	/* tmp points to a struct rndis_packet_msg_type */
 	__le32		*tmp = (void *) skb->data;
 
 	/* MessageType, MessageLength */
 	if (cpu_to_le32(REMOTE_NDIS_PACKET_MSG)
-			!= get_unaligned(tmp++))
+			!= get_unaligned(tmp++)) {
+		dev_kfree_skb_any(skb);
 		return -EINVAL;
+	}
 	tmp++;
 
 	/* DataOffset, DataLength */
-	if (!skb_pull(skb, get_unaligned_le32(tmp++) + 8))
+	if (!skb_pull(skb, get_unaligned_le32(tmp++) + 8)) {
+		dev_kfree_skb_any(skb);
 		return -EOVERFLOW;
+	}
 	skb_trim(skb, get_unaligned_le32(tmp++));
 
+	skb_queue_tail(list, skb);
 	return 0;
 }
 

drivers/usb/gadget/rndis.h

@@ -251,7 +251,8 @@ int  rndis_set_param_vendor (u8 configNr, u32 vendorID,
 			    const char *vendorDescr);
 int  rndis_set_param_medium (u8 configNr, u32 medium, u32 speed);
 void rndis_add_hdr (struct sk_buff *skb);
-int rndis_rm_hdr (struct sk_buff *skb);
+int rndis_rm_hdr(struct gether *port, struct sk_buff *skb,
+			struct sk_buff_head *list);
 u8   *rndis_get_next_response (int configNr, u32 *length);
 void rndis_free_response (int configNr, u8 *buf);
 

drivers/usb/gadget/u_ether.c

@@ -37,8 +37,9 @@
  * one (!) network link through the USB gadget stack, normally "usb0".
  *
  * The control and data models are handled by the function driver which
- * connects to this code; such as CDC Ethernet, "CDC Subset", or RNDIS.
- * That includes all descriptor and endpoint management.
+ * connects to this code; such as CDC Ethernet (ECM or EEM),
+ * "CDC Subset", or RNDIS.  That includes all descriptor and endpoint
+ * management.
  *
  * Link level addressing is handled by this component using module
  * parameters; if no such parameters are provided, random link level
@@ -68,9 +69,13 @@ struct eth_dev {
 	struct list_head	tx_reqs, rx_reqs;
 	atomic_t		tx_qlen;
 
+	struct sk_buff_head	rx_frames;
+
 	unsigned		header_len;
-	struct sk_buff		*(*wrap)(struct sk_buff *skb);
-	int			(*unwrap)(struct sk_buff *skb);
+	struct sk_buff		*(*wrap)(struct gether *, struct sk_buff *skb);
+	int			(*unwrap)(struct gether *,
+						struct sk_buff *skb,
+						struct sk_buff_head *list);
 
 	struct work_struct	work;
 
@@ -269,7 +274,7 @@ enomem:
 
 static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 {
-	struct sk_buff	*skb = req->context;
+	struct sk_buff	*skb = req->context, *skb2;
 	struct eth_dev	*dev = ep->driver_data;
 	int		status = req->status;
 
@@ -278,26 +283,47 @@ static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 	/* normal completion */
 	case 0:
 		skb_put(skb, req->actual);
-		if (dev->unwrap)
-			status = dev->unwrap(skb);
-		if (status < 0
-				|| ETH_HLEN > skb->len
-				|| skb->len > ETH_FRAME_LEN) {
-			dev->net->stats.rx_errors++;
-			dev->net->stats.rx_length_errors++;
-			DBG(dev, "rx length %d\n", skb->len);
-			break;
-		}
 
-		skb->protocol = eth_type_trans(skb, dev->net);
-		dev->net->stats.rx_packets++;
-		dev->net->stats.rx_bytes += skb->len;
+		if (dev->unwrap) {
+			unsigned long	flags;
 
-		/* no buffer copies needed, unless hardware can't
-		 * use skb buffers.
-		 */
-		status = netif_rx(skb);
+			spin_lock_irqsave(&dev->lock, flags);
+			if (dev->port_usb) {
+				status = dev->unwrap(dev->port_usb,
+							skb,
+							&dev->rx_frames);
+			} else {
+				dev_kfree_skb_any(skb);
+				status = -ENOTCONN;
+			}
+			spin_unlock_irqrestore(&dev->lock, flags);
+		} else {
+			skb_queue_tail(&dev->rx_frames, skb);
+		}
 		skb = NULL;
+
+		skb2 = skb_dequeue(&dev->rx_frames);
+		while (skb2) {
+			if (status < 0
+					|| ETH_HLEN > skb2->len
+					|| skb2->len > ETH_FRAME_LEN) {
+				dev->net->stats.rx_errors++;
+				dev->net->stats.rx_length_errors++;
+				DBG(dev, "rx length %d\n", skb2->len);
+				dev_kfree_skb_any(skb2);
+				goto next_frame;
+			}
+			skb2->protocol = eth_type_trans(skb2, dev->net);
+			dev->net->stats.rx_packets++;
+			dev->net->stats.rx_bytes += skb2->len;
+
+			/* no buffer copies needed, unless hardware can't
+			 * use skb buffers.
+			 */
+			status = netif_rx(skb2);
+next_frame:
+			skb2 = skb_dequeue(&dev->rx_frames);
+		}
 		break;
 
 	/* software-driven interface shutdown */
@@ -537,14 +563,15 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 	 * or there's not enough space for extra headers we need
 	 */
 	if (dev->wrap) {
-		struct sk_buff	*skb_new;
+		unsigned long	flags;
 
-		skb_new = dev->wrap(skb);
-		if (!skb_new)
+		spin_lock_irqsave(&dev->lock, flags);
+		if (dev->port_usb)
+			skb = dev->wrap(dev->port_usb, skb);
+		spin_unlock_irqrestore(&dev->lock, flags);
+		if (!skb)
 			goto drop;
 
-		dev_kfree_skb_any(skb);
-		skb = skb_new;
 		length = skb->len;
 	}
 	req->buf = skb->data;
@@ -578,9 +605,9 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 	}
 
 	if (retval) {
+		dev_kfree_skb_any(skb);
 drop:
 		dev->net->stats.tx_dropped++;
-		dev_kfree_skb_any(skb);
 		spin_lock_irqsave(&dev->req_lock, flags);
 		if (list_empty(&dev->tx_reqs))
 			netif_start_queue(net);
@@ -753,6 +780,8 @@ int __init gether_setup(struct usb_gadget *g, u8 ethaddr[ETH_ALEN])
 	INIT_LIST_HEAD(&dev->tx_reqs);
 	INIT_LIST_HEAD(&dev->rx_reqs);
 
+	skb_queue_head_init(&dev->rx_frames);
+
 	/* network device setup */
 	dev->net = net;
 	strcpy(net->name, "usb%d");

drivers/usb/gadget/u_ether.h

@@ -60,12 +60,13 @@ struct gether {
 
 	u16				cdc_filter;
 
-	/* hooks for added framing, as needed for RNDIS and EEM.
-	 * we currently don't support multiple frames per SKB.
-	 */
+	/* hooks for added framing, as needed for RNDIS and EEM. */
 	u32				header_len;
-	struct sk_buff			*(*wrap)(struct sk_buff *skb);
-	int				(*unwrap)(struct sk_buff *skb);
+	struct sk_buff			*(*wrap)(struct gether *port,
+						struct sk_buff *skb);
+	int				(*unwrap)(struct gether *port,
+						struct sk_buff *skb,
+						struct sk_buff_head *list);
 
 	/* called on network open/close */
 	void				(*open)(struct gether *);
@@ -109,6 +110,7 @@ static inline bool can_support_ecm(struct usb_gadget *gadget)
 /* 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]);
+int eem_bind_config(struct usb_configuration *c);
 
 #ifdef CONFIG_USB_ETH_RNDIS