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 {