USB: export <linux/usb_gadgetfs> as <linux/usb/gadgetfs.h>

Make sure gadgetfs userspace interface is properly exported:

 - Move <linux/usb_gadgetfs.h> to <linux/usb/gadgetfs.h>;
 - Export it using Kbuild;
 - Add an #include guard;
 - Correct some internal documentation;
 - Update struct layout so it's the same on 32/64 bit kernels.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/usb/Kbuild

@@ -1,5 +1,6 @@
 unifdef-y += audio.h
 unifdef-y += cdc.h
 unifdef-y += ch9.h
+unifdef-y += gadgetfs.h
 unifdef-y += midi.h
 

include/linux/usb/gadgetfs.h

@@ -0,0 +1,81 @@
+#ifndef __LINUX_USB_GADGETFS_H
+#define __LINUX_USB_GADGETFS_H
+
+#include <asm/types.h>
+#include <asm/ioctl.h>
+
+#include <linux/usb/ch9.h>
+
+/*
+ * Filesystem based user-mode API to USB Gadget controller hardware
+ *
+ * Other than ep0 operations, most things are done by read() and write()
+ * on endpoint files found in one directory.  They are configured by
+ * writing descriptors, and then may be used for normal stream style
+ * i/o requests.  When ep0 is configured, the device can enumerate;
+ * when it's closed, the device disconnects from usb.  Operations on
+ * ep0 require ioctl() operations.
+ *
+ * Configuration and device descriptors get written to /dev/gadget/$CHIP,
+ * which may then be used to read usb_gadgetfs_event structs.  The driver
+ * may activate endpoints as it handles SET_CONFIGURATION setup events,
+ * or earlier; writing endpoint descriptors to /dev/gadget/$ENDPOINT
+ * then performing data transfers by reading or writing.
+ */
+
+/*
+ * Events are delivered on the ep0 file descriptor, when the user mode driver
+ * reads from this file descriptor after writing the descriptors.  Don't
+ * stop polling this descriptor.
+ */
+
+enum usb_gadgetfs_event_type {
+	GADGETFS_NOP = 0,
+
+	GADGETFS_CONNECT,
+	GADGETFS_DISCONNECT,
+	GADGETFS_SETUP,
+	GADGETFS_SUSPEND,
+	// and likely more !
+};
+
+/* NOTE:  this structure must stay the same size and layout on
+ * both 32-bit and 64-bit kernels.
+ */
+struct usb_gadgetfs_event {
+	union {
+		// NOP, DISCONNECT, SUSPEND: nothing
+		// ... some hardware can't report disconnection
+
+		// CONNECT: just the speed
+		enum usb_device_speed	speed;
+
+		// SETUP: packet; DATA phase i/o precedes next event
+		// (setup.bmRequestType & USB_DIR_IN) flags direction
+		// ... includes SET_CONFIGURATION, SET_INTERFACE
+		struct usb_ctrlrequest	setup;
+	} u;
+	enum usb_gadgetfs_event_type	type;
+};
+
+
+/* endpoint ioctls */
+
+/* IN transfers may be reported to the gadget driver as complete
+ *	when the fifo is loaded, before the host reads the data;
+ * OUT transfers may be reported to the host's "client" driver as
+ *	complete when they're sitting in the FIFO unread.
+ * THIS returns how many bytes are "unclaimed" in the endpoint fifo
+ * (needed for precise fault handling, when the hardware allows it)
+ */
+#define	GADGETFS_FIFO_STATUS	_IO('g',1)
+
+/* discards any unclaimed data in the fifo. */
+#define	GADGETFS_FIFO_FLUSH	_IO('g',2)
+
+/* resets endpoint halt+toggle; used to implement set_interface.
+ * some hardware (like pxa2xx) can't support this.
+ */
+#define	GADGETFS_CLEAR_HALT	_IO('g',3)
+
+#endif /* __LINUX_USB_GADGETFS_H */