i2c: Add bus driver for for OSIF USB i2c device.

OSIF, Open Source InterFace, is a USB based i2c bus master. The
origional design was based on i2c-tiny-usb, but more modern versions
of the firmware running on the MegaAVR microcontroller use a different
protocol over the USB. This code is based on Barry Carter
<[e-mail]> driver.

Signed-off-by: Andrew Lunn <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/busses/Kconfig

···
 	  This support is also available as a module.  If so, the module
 	  will be called i2c-parport-light.
 
+config I2C_ROBOTFUZZ_OSIF
+	tristate "RobotFuzz Open Source InterFace USB adapter"
+	depends on USB
+	help
+	  If you say yes to this option, support will be included for the
+	  RobotFuzz Open Source InterFace USB to I2C interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-osif.
+
 config I2C_TAOS_EVM
 	tristate "TAOS evaluation module"
 	depends on TTY

drivers/i2c/busses/Makefile

···
 obj-$(CONFIG_I2C_DIOLAN_U2C)	+= i2c-diolan-u2c.o
 obj-$(CONFIG_I2C_PARPORT)	+= i2c-parport.o
 obj-$(CONFIG_I2C_PARPORT_LIGHT)	+= i2c-parport-light.o
+obj-$(CONFIG_I2C_ROBOTFUZZ_OSIF)	+= i2c-robotfuzz-osif.o
 obj-$(CONFIG_I2C_TAOS_EVM)	+= i2c-taos-evm.o
 obj-$(CONFIG_I2C_TINY_USB)	+= i2c-tiny-usb.o
 obj-$(CONFIG_I2C_VIPERBOARD)	+= i2c-viperboard.o

drivers/i2c/busses/i2c-robotfuzz-osif.c

···
+/*
+ * Driver for RobotFuzz OSIF
+ *
+ * Copyright (c) 2013 Andrew Lunn <[e-mail]>
+ * Copyright (c) 2007 Barry Carter <[e-mail]>
+ *
+ * Based on the i2c-tiny-usb by
+ *
+ * Copyright (C) 2006 Til Harbaum ([e-mail])
+ *
+ *	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, version 2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#define OSIFI2C_READ		20
+#define OSIFI2C_WRITE		21
+#define OSIFI2C_STOP		22
+#define OSIFI2C_STATUS		23
+#define OSIFI2C_SET_BIT_RATE	24
+
+#define STATUS_ADDRESS_ACK	0
+#define STATUS_ADDRESS_NAK	2
+
+struct osif_priv {
+	struct usb_device *usb_dev;
+	struct usb_interface *interface;
+	struct i2c_adapter adapter;
+	unsigned char status;
+};
+
+static int osif_usb_read(struct i2c_adapter *adapter, int cmd,
+			 int value, int index, void *data, int len)
+{
+	struct osif_priv *priv = adapter->algo_data;
+
+	return usb_control_msg(priv->usb_dev, usb_rcvctrlpipe(priv->usb_dev, 0),
+			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
+			       USB_DIR_IN, value, index, data, len, 2000);
+}
+
+static int osif_usb_write(struct i2c_adapter *adapter, int cmd,
+			  int value, int index, void *data, int len)
+{
+
+	struct osif_priv *priv = adapter->algo_data;
+
+	return usb_control_msg(priv->usb_dev, usb_sndctrlpipe(priv->usb_dev, 0),
+			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
+			       value, index, data, len, 2000);
+}
+
+static int osif_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
+			 int num)
+{
+	struct osif_priv *priv = adapter->algo_data;
+	struct i2c_msg *pmsg;
+	int ret = 0;
+	int i, cmd;
+
+	for (i = 0; ret >= 0 && i < num; i++) {
+		pmsg = &msgs[i];
+
+		if (pmsg->flags & I2C_M_RD) {
+			cmd = OSIFI2C_READ;
+
+			ret = osif_usb_read(adapter, cmd, pmsg->flags,
+					    pmsg->addr, pmsg->buf,
+					    pmsg->len);
+			if (ret != pmsg->len) {
+				dev_err(&adapter->dev, "failure reading data\n");
+				return -EREMOTEIO;
+			}
+		} else {
+			cmd = OSIFI2C_WRITE;
+
+			ret = osif_usb_write(adapter, cmd, pmsg->flags,
+					     pmsg->addr, pmsg->buf, pmsg->len);
+			if (ret != pmsg->len) {
+				dev_err(&adapter->dev, "failure writing data\n");
+				return -EREMOTEIO;
+			}
+		}
+
+		ret = osif_usb_read(adapter, OSIFI2C_STOP, 0, 0, NULL, 0);
+		if (ret) {
+			dev_err(&adapter->dev, "failure sending STOP\n");
+			return -EREMOTEIO;
+		}
+
+		/* read status */
+		ret = osif_usb_read(adapter, OSIFI2C_STATUS, 0, 0,
+				    &priv->status, 1);
+		if (ret != 1) {
+			dev_err(&adapter->dev, "failure reading status\n");
+			return -EREMOTEIO;
+		}
+
+		if (priv->status != STATUS_ADDRESS_ACK) {
+			dev_dbg(&adapter->dev, "status = %d\n", priv->status);
+			return -EREMOTEIO;
+		}
+	}
+
+	return i;
+}
+
+static u32 osif_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm osif_algorithm = {
+	.master_xfer	= osif_xfer,
+	.functionality	= osif_func,
+};
+
+#define USB_OSIF_VENDOR_ID	0x1964
+#define USB_OSIF_PRODUCT_ID	0x0001
+
+static struct usb_device_id osif_table[] = {
+	{ USB_DEVICE(USB_OSIF_VENDOR_ID, USB_OSIF_PRODUCT_ID) },
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, osif_table);
+
+static int osif_probe(struct usb_interface *interface,
+			     const struct usb_device_id *id)
+{
+	int ret;
+	struct osif_priv *priv;
+	u16 version;
+
+	priv = devm_kzalloc(&interface->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->usb_dev = usb_get_dev(interface_to_usbdev(interface));
+	priv->interface = interface;
+
+	usb_set_intfdata(interface, priv);
+
+	priv->adapter.owner = THIS_MODULE;
+	priv->adapter.class = I2C_CLASS_HWMON;
+	priv->adapter.algo = &osif_algorithm;
+	priv->adapter.algo_data = priv;
+	snprintf(priv->adapter.name, sizeof(priv->adapter.name),
+		 "OSIF at bus %03d device %03d",
+		 priv->usb_dev->bus->busnum, priv->usb_dev->devnum);
+
+	/*
+	 * Set bus frequency. The frequency is:
+	 * 120,000,000 / ( 16 + 2 * div * 4^prescale).
+	 * Using dev = 52, prescale = 0 give 100KHz */
+	ret = osif_usb_read(&priv->adapter, OSIFI2C_SET_BIT_RATE, 52, 0,
+			    NULL, 0);
+	if (ret) {
+		dev_err(&interface->dev, "failure sending bit rate");
+		usb_put_dev(priv->usb_dev);
+		return ret;
+	}
+
+	i2c_add_adapter(&(priv->adapter));
+
+	version = le16_to_cpu(priv->usb_dev->descriptor.bcdDevice);
+	dev_info(&interface->dev,
+		 "version %x.%02x found at bus %03d address %03d",
+		 version >> 8, version & 0xff,
+		 priv->usb_dev->bus->busnum, priv->usb_dev->devnum);
+
+	return 0;
+}
+
+static void osif_disconnect(struct usb_interface *interface)
+{
+	struct osif_priv *priv = usb_get_intfdata(interface);
+
+	i2c_del_adapter(&(priv->adapter));
+	usb_set_intfdata(interface, NULL);
+	usb_put_dev(priv->usb_dev);
+}
+
+static struct usb_driver osif_driver = {
+	.name		= "RobotFuzz Open Source InterFace, OSIF",
+	.probe		= osif_probe,
+	.disconnect	= osif_disconnect,
+	.id_table	= osif_table,
+};
+
+module_usb_driver(osif_driver);
+
+MODULE_AUTHOR("Andrew Lunn <[e-mail]>");
+MODULE_AUTHOR("Barry Carter <[e-mail]>");
+MODULE_DESCRIPTION("RobotFuzz OSIF driver");
+MODULE_LICENSE("GPL v2");