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>

1 files changed, 23 insertions, 3 deletions

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 3537d915d275..4d8ab470f087 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/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