diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index 533f127..64c9f2e 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -181,6 +181,15 @@ config USB_SERIAL_FTDI_SIO
 	  To compile this driver as a module, choose M here: the
 	  module will be called ftdi_sio.
 
+config USB_SERIAL_FTDI_SIO_CBUS_GPIO
+	bool "USB FDTI CBUS GPIO support"
+	depends on USB_SERIAL_FTDI_SIO
+	depends on GPIOLIB
+	help
+	  Say yes here to add support for the CBUS bit-bang mode, allowing CBUS
+	  pins to act as GPIOs. Note that pins must first be configured for GPIO
+	  in the device's EEPROM. The FT232R and FT-X series support this mode.
+
 config USB_SERIAL_VISOR
 	tristate "USB Handspring Visor / Palm m50x / Sony Clie Driver"
 	help
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index b5cef32..e90cae6 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -33,6 +33,7 @@
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>
+#include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/mutex.h>
@@ -40,12 +41,21 @@
 #include <linux/usb.h>
 #include <linux/serial.h>
 #include <linux/usb/serial.h>
+
 #include "ftdi_sio.h"
 #include "ftdi_sio_ids.h"
 
 #define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>, Bill Ryder <bryder@sgi.com>, Kuba Ober <kuba@mareimbrium.org>, Andreas Mohr, Johan Hovold <jhovold@gmail.com>"
 #define DRIVER_DESC "USB FTDI Serial Converters Driver"
 
+#define FTDI_CBUS_PIN_COUNT 4
+
+struct ftdi_gpiochip {
+	struct gpio_chip gc;
+	struct usb_serial_port *port;
+	unsigned int cbus_map[FTDI_CBUS_PIN_COUNT];
+	unsigned long cbus_mask;
+};
 
 struct ftdi_private {
 	enum ftdi_chip_type chip_type;
@@ -72,6 +82,8 @@ struct ftdi_private {
 	unsigned int latency;		/* latency setting in use */
 	unsigned short max_packet_size;
 	struct mutex cfg_lock; /* Avoid mess by parallel calls of config ioctl() and change_speed() */
+
+	struct ftdi_gpiochip *fgc;
 };
 
 /* struct ftdi_sio_quirk is used by devices requiring special attention. */
@@ -1528,6 +1540,224 @@ static int get_lsr_info(struct usb_serial_port *port,
 	return 0;
 }
 
+#ifdef CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO
+
+#define FTX_CBUS_MUX_EEPROM_ADDR 0x1a
+
+static int ftdi_read_eeprom(struct usb_device *udev, unsigned int off,
+			    void *val, size_t bytes)
+{
+	unsigned int read = 0;
+
+	if (bytes % 2) /* 16-bit word eeprom */
+		bytes--;
+
+	while (read < bytes) {
+		int rv;
+
+		rv = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
+				     FTDI_SIO_READ_EEPROM_REQUEST,
+				     FTDI_SIO_READ_EEPROM_REQUEST_TYPE,
+				     0, (off + read) / 2, val + read, 2,
+				     WDR_TIMEOUT);
+		if (rv < 0)
+			break;
+
+		read += 2;
+	}
+
+	return read;
+}
+
+static int ftdi_set_bitmode(struct usb_serial_port *port, u8 bitmask,
+			    u8 bitmode)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	__u16 urb_value = 0;
+
+	urb_value = bitmode << 8 | bitmask;
+
+	if (usb_control_msg(port->serial->dev,
+			    usb_sndctrlpipe(port->serial->dev, 0),
+			    FTDI_SIO_SET_BITMODE_REQUEST,
+			    FTDI_SIO_SET_BITMODE_REQUEST_TYPE,
+			    urb_value, priv->interface, NULL, 0,
+			    WDR_SHORT_TIMEOUT) < 0) {
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int ftdi_read_pins(struct usb_serial_port *port, u8 *val)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	unsigned char *buf;
+
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	if (usb_control_msg(port->serial->dev,
+			    usb_rcvctrlpipe(port->serial->dev, 0),
+			    FTDI_SIO_READ_PINS_REQUEST,
+			    FTDI_SIO_READ_PINS_REQUEST_TYPE,
+			    0, priv->interface, buf, 1, WDR_TIMEOUT) < 0) {
+		kfree(buf);
+		return -EIO;
+	}
+
+	*val = buf[0];
+	kfree(buf);
+
+	return 0;
+}
+
+static int ftdi_cbus_gpio_dir_out(struct gpio_chip *gc, unsigned gpio, int val)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];
+
+	/*
+	 * CBUS mask is an 8-bit register controlling the direction and value
+	 * of CBUS pins in Bit-Bang mode. cf application note AN_373/AN_232R-01.
+	 * | bit 7 | bit 6 | bit 5 | bit 4 | bit 3 | bit 2 | bit 1 | bit 0 |
+	 * | CBUS3 | CBUS2 | CBUS1 | CBUS0 | CBUS3 | CBUS2 | CBUS1 | CBUS0 |
+	 * |  I/O  |  I/O  |  I/O  |  I/O  | Hi/Lo | Hi/Lo | Hi/Lo | Hi/Lo |
+	 */
+	set_bit(cbus_idx + 4, &fgc->cbus_mask); /* direction */
+	set_bit(cbus_idx, &fgc->cbus_mask); /* value */
+
+	return ftdi_set_bitmode(fgc->port, fgc->cbus_mask,
+				FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_cbus_gpio_dir_in(struct gpio_chip *gc, unsigned gpio)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];
+
+	clear_bit(cbus_idx + 4, &fgc->cbus_mask);
+
+	return ftdi_set_bitmode(fgc->port, fgc->cbus_mask,
+				FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_cbus_gpio_get(struct gpio_chip *gc, unsigned gpio)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];
+	u8 val = 0;
+	int rv;
+
+	rv = ftdi_read_pins(fgc->port, &val);
+	if (rv)
+		return rv;
+
+	return !!(val & BIT(cbus_idx));
+}
+
+static void ftdi_cbus_gpio_set(struct gpio_chip *gc, unsigned gpio, int val)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+
+	if (val)
+		set_bit(fgc->cbus_map[gpio], &fgc->cbus_mask);
+	else
+		clear_bit(fgc->cbus_map[gpio], &fgc->cbus_mask);
+
+	ftdi_set_bitmode(fgc->port, fgc->cbus_mask, FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_register_cbus_gpiochip(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_device *udev = port->serial->dev;
+	struct ftdi_gpiochip *fgc;
+	int rv = 0;
+
+	fgc = kzalloc(sizeof(*fgc), GFP_KERNEL);
+	if (!fgc)
+		return -ENOMEM;
+
+	if (priv->chip_type == FTX) {
+		unsigned char *cbus_mux;
+		unsigned int i;
+
+		/*
+		 * Each individual CBUS pin is controlled by a separate 8-bit
+		 * MUX control value stored in the EEPROM, starting at 0x1a:
+		 * | 0x1a CBUS0 | 0x1b CBUS1 | 0x1c CBUS2 | 0x1d CBUS3 | ...
+		 * cf application note AN_201.
+		 */
+
+		cbus_mux = kmalloc(FTDI_CBUS_PIN_COUNT, GFP_KERNEL);
+		if (!cbus_mux)
+			return -ENOMEM;
+
+		rv = ftdi_read_eeprom(udev, FTX_CBUS_MUX_EEPROM_ADDR, cbus_mux,
+				      FTDI_CBUS_PIN_COUNT);
+		if (rv < 0) {
+			dev_err(&udev->dev, "Unable to read CBUS config\n");
+			kfree(cbus_mux);
+			goto exit_release;
+		}
+
+		for (i = 0; i < rv; i++) {
+			if (cbus_mux[i] == FTX_CBUS_MUX_IO)
+				fgc->cbus_map[fgc->gc.ngpio++] = i;
+		}
+
+		rv = 0;
+		kfree(cbus_mux);
+	}
+
+	if (!fgc->gc.ngpio)
+		goto exit_release;
+
+	fgc->gc.label = "ftdi-cbus-gpio";
+	fgc->gc.direction_input = ftdi_cbus_gpio_dir_in;
+	fgc->gc.direction_output = ftdi_cbus_gpio_dir_out;
+	fgc->gc.set = ftdi_cbus_gpio_set;
+	fgc->gc.get = ftdi_cbus_gpio_get;
+	fgc->gc.can_sleep = true;
+	fgc->gc.parent = &udev->dev;
+	fgc->gc.base = -1;
+	fgc->gc.owner = THIS_MODULE;
+	fgc->port = port;
+
+	rv = gpiochip_add_data(&fgc->gc, fgc);
+	if (rv) {
+		dev_err(&udev->dev, "Unable to add gpiochip\n");
+		goto exit_release;
+	}
+
+	priv->fgc = fgc;
+
+	dev_info(&udev->dev,
+		 "FTDI USB GPIO controller Registered, base=%d, ngpio=%u\n",
+		 fgc->gc.base, fgc->gc.ngpio);
+
+	return 0;
+
+exit_release:
+	kfree(fgc);
+	return rv;
+}
+
+static void ftdi_unregister_cbus_gpiochip(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct ftdi_gpiochip *fgc = priv->fgc;
+
+	if (!fgc)
+		return;
+
+	gpiochip_remove(&fgc->gc);
+	kfree(fgc);
+}
+
+#endif /*  CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO */
 
 /* Determine type of FTDI chip based on USB config and descriptor. */
 static void ftdi_determine_type(struct usb_serial_port *port)
@@ -1813,6 +2043,10 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 		priv->latency = 16;
 	write_latency_timer(port);
 	create_sysfs_attrs(port);
+#ifdef CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO
+	ftdi_register_cbus_gpiochip(port);
+#endif
+
 	return 0;
 }
 
@@ -1930,6 +2164,10 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 
+#ifdef CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO
+	ftdi_unregister_cbus_gpiochip(port);
+#endif
+
 	remove_sysfs_attrs(port);
 
 	kfree(priv);
diff --git a/drivers/usb/serial/ftdi_sio.h b/drivers/usb/serial/ftdi_sio.h
index dcd0b6e..3bd248f 100644
--- a/drivers/usb/serial/ftdi_sio.h
+++ b/drivers/usb/serial/ftdi_sio.h
@@ -36,6 +36,10 @@
 #define FTDI_SIO_SET_ERROR_CHAR		7 /* Set the error character */
 #define FTDI_SIO_SET_LATENCY_TIMER	9 /* Set the latency timer */
 #define FTDI_SIO_GET_LATENCY_TIMER	10 /* Get the latency timer */
+#define FTDI_SIO_SET_BITMODE		11 /* Set the bitmode */
+#define FTDI_SIO_READ_PINS		12 /* Read pins in bitmode */
+#define FTDI_SIO_READ_EEPROM		0x90 /* Read eeprom */
+#define FTDI_SIO_WRITE_EEPROM		0x91 /* Write eeprom */
 
 /* Interface indices for FT2232, FT2232H and FT4232H devices */
 #define INTERFACE_A		1
@@ -400,6 +404,60 @@ enum ftdi_sio_baudrate {
  *
  */
 
+ /* FTDI_SIO_READ_EEPROM */
+#define FTDI_SIO_READ_EEPROM_REQUEST_TYPE 0xc0
+#define FTDI_SIO_READ_EEPROM_REQUEST FTDI_SIO_READ_EEPROM
+/*
+ *  BmRequestType:   1100 0000b
+ *  bRequest:        FTDI_SIO_READ_EEPROM
+ *  wValue:          0
+ *  wIndex:          Word Index
+ *  wLength:         2
+ *  Data:            return data (a word)
+ *
+ */
+
+/* FTDI_SIO_WRITE_EEPROM */
+#define FTDI_SIO_WRITE_EEPROM_REQUEST_TYPE 0x40
+#define FTDI_SIO_WRITE_EEPROM_REQUEST FTDI_SIO_WRITE_EEPROM
+/*
+ *  BmRequestType:   0100 0000b
+ *  bRequest:        FTDI_SIO_WRITE_EEPROM
+ *  wValue:          Data (word)
+ *  wIndex:          Word Index
+ *  wLength:         0
+ *  Data:            None
+ *
+ */
+
+ /* FTDI_SIO_SET_BITMODE */
+#define FTDI_SIO_SET_BITMODE_REQUEST_TYPE 0x40
+#define FTDI_SIO_SET_BITMODE_REQUEST FTDI_SIO_SET_BITMODE
+#define FTDI_SIO_BITMODE_RESET 0x00
+#define FTDI_SIO_BITMODE_CBUS 0x20
+/*
+ *  BmRequestType:   0100 0000b
+ *  bRequest:        FTDI_SIO_SET_BITMODE
+ *  wValue:          [0-7] bitmask, [8-15] bitmode
+ *  wIndex:          Port
+ *  wLength:         0
+ *  Data:            None
+ *
+ */
+
+/* FTDI_SIO_READ_PINS */
+#define FTDI_SIO_READ_PINS_REQUEST_TYPE 0xC0
+#define FTDI_SIO_READ_PINS_REQUEST FTDI_SIO_READ_PINS
+/*
+ *  BmRequestType:   1100 0000b
+ *  bRequest:        FTDI_SIO_READ_PINS
+ *  wValue:          0
+ *  wIndex:          Port
+ *  wLength:         2
+ *  Data:            return data (a word)
+ *
+ */
+
 /* FTDI_SIO_GET_MODEM_STATUS */
 /* Retrieve the current value of the modem status register */
 
@@ -563,3 +621,28 @@ enum ftdi_sio_baudrate {
  * B2..7	Length of message - (not including Byte 0)
  *
  */
+
+enum ftdi_ftx_cbus_mux {
+	FTX_CBUS_MUX_TRISTATE,
+	FTX_CBUS_MUX_RXLED,
+	FTX_CBUS_MUX_TXLED,
+	FTX_CBUS_MUX_TXRXLED,
+	FTX_CBUS_MUX_PWREN,
+	FTX_CBUS_MUX_SLEEP,
+	FTX_CBUS_MUX_DRIVE0,
+	FTX_CBUS_MUX_DRIVE1,
+	FTX_CBUS_MUX_IO,
+	FTX_CBUS_MUX_TXDEN,
+	FTX_CBUS_MUX_CLK24,
+	FTX_CBUS_MUX_CLK12,
+	FTX_CBUS_MUX_CLK6,
+	FTX_CBUS_MUX_BCD_CHARGER,
+	FTX_CBUS_MUX_BCD_CHARGER_N,
+	FTX_CBUS_MUX_I2C_TXE,
+	FTX_CBUS_MUX_I2C_RXF,
+	FTX_CBUS_MUX_VBUS_SENSE,
+	FTX_CBUS_MUX_BITBANG_WR,
+	FTX_CBUS_MUX_BITBANG_RD,
+	FTX_CBUS_MUX_TIMESTAMP,
+	FTX_CBUS_MUX_KEEP_AWAKE
+};
