usb-serial: add support for USB Wishbone-serial adapters

Wishbone is an open hardware SoC bus commonly used in FPGA
designs. Bus access can be serialized using the Etherbone
protocol <http://www.ohwr.org/projects/etherbone-core>.

This driver is intended to be used with devices which attach
their internal Wishbone bus to a USB serial interface using
the Etherbone protocol. A userspace library is required to
speak the protocol made available by this driver as ttyUSBx.

Signed-off-by: Wesley W. Terpstra <w.terpstra@gsi.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/Kconfig

@@ -667,6 +667,23 @@ config USB_SERIAL_ZIO
 	  To compile this driver as a module, choose M here: the
 	  module will be called zio.
 
+config USB_SERIAL_WISHBONE
+	tristate "USB-Wishbone adapter interface driver"
+	help
+	  Say Y here if you want to use a USB attached Wishbone bus.
+
+	  Wishbone is an open hardware SoC bus commonly used in FPGA
+	  designs. Bus access can be serialized using the Etherbone
+	  protocol <http://www.ohwr.org/projects/etherbone-core>.
+
+	  This driver is intended to be used with devices which attach
+	  their internal Wishbone bus to a USB serial interface using
+	  the Etherbone protocol. A userspace library is required to
+	  speak the protocol made available by this driver as ttyUSBx.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called wishbone-serial.
+
 config USB_SERIAL_ZTE
 	tristate "ZTE USB serial driver"
 	help

drivers/usb/serial/Makefile

@@ -58,6 +58,7 @@ obj-$(CONFIG_USB_SERIAL_SYMBOL)			+= symbolserial.o
 obj-$(CONFIG_USB_SERIAL_WWAN)			+= usb_wwan.o
 obj-$(CONFIG_USB_SERIAL_TI)			+= ti_usb_3410_5052.o
 obj-$(CONFIG_USB_SERIAL_VISOR)			+= visor.o
+obj-$(CONFIG_USB_SERIAL_WISHBONE)		+= wishbone-serial.o
 obj-$(CONFIG_USB_SERIAL_WHITEHEAT)		+= whiteheat.o
 obj-$(CONFIG_USB_SERIAL_XIRCOM)			+= keyspan_pda.o
 obj-$(CONFIG_USB_SERIAL_VIVOPAY_SERIAL)		+= vivopay-serial.o

drivers/usb/serial/wishbone-serial.c

@@ -0,0 +1,95 @@
+/*
+ * USB Wishbone-Serial adapter driver
+ *
+ * Copyright (C) 2013 Wesley W. Terpstra <w.terpstra@gsi.de>
+ * Copyright (C) 2013 GSI Helmholtz Centre for Heavy Ion Research GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+#include <linux/uaccess.h>
+
+#define GSI_VENDOR_OPENCLOSE 0xB0
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE_AND_INTERFACE_INFO(0x1D50, 0x6062, 0xFF, 0xFF, 0xFF) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+/*
+ * Etherbone must be told that a new stream has begun before data arrives.
+ * This is necessary to restart the negotiation of Wishbone bus parameters.
+ * Similarly, when the stream ends, Etherbone must be told so that the cycle
+ * line can be driven low in the case that userspace failed to do so.
+ */
+static int usb_gsi_openclose(struct usb_serial_port *port, int value)
+{
+	struct usb_device *dev = port->serial->dev;
+
+	return usb_control_msg(
+		dev,
+		usb_sndctrlpipe(dev, 0), /* Send to EP0OUT */
+		GSI_VENDOR_OPENCLOSE,
+		USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
+		value, /* wValue = device is open(1) or closed(0) */
+		port->serial->interface->cur_altsetting->desc.bInterfaceNumber,
+		0, 0,  /* There is no data stage */
+		5000); /* Timeout till operation fails */
+}
+
+static int wishbone_serial_open(struct tty_struct *tty,
+				struct usb_serial_port *port)
+{
+	int retval;
+
+	retval = usb_gsi_openclose(port, 1);
+	if (retval) {
+		dev_err(&port->serial->dev->dev,
+		       "Could not mark device as open (%d)\n",
+		       retval);
+		return retval;
+	}
+
+	retval = usb_serial_generic_open(tty, port);
+	if (retval)
+		usb_gsi_openclose(port, 0);
+
+	return retval;
+}
+
+static void wishbone_serial_close(struct usb_serial_port *port)
+{
+	usb_serial_generic_close(port);
+	usb_gsi_openclose(port, 0);
+}
+
+static struct usb_serial_driver wishbone_serial_device = {
+	.driver = {
+		.owner =	THIS_MODULE,
+		.name =		"wishbone_serial",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.open =			&wishbone_serial_open,
+	.close =		&wishbone_serial_close,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&wishbone_serial_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR("Wesley W. Terpstra <w.terpstra@gsi.de>");
+MODULE_DESCRIPTION("USB Wishbone-Serial adapter");
+MODULE_LICENSE("GPL");