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>

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

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;
+}

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 */