[PATCH] USB: ftdi_sio: add GPIO support

[Sascha Silbe <x-linux@xxxxxxxxxxxxxx>]

Most FTDI USB serial / parallel adapter chips support an asynchronous
"bitbang" mode. Make this functionality available as a GPIO controller
so they can be used with the Linux GPIO API instead of requiring
special user space software that only works with this particular
family of chips.

The chips can operate either in regular or in bitbang mode. Care was
taken to prevent using GPIOs if the serial device is in use and vice
versa.

At least the FT245RL will toggle several of its pins multiple times
during initialisation (even if connected to a dumb USB power supply,
so not a driver issue). Using synchronous bitbang mode might help
coping with this if the hardware connected to the FTDI chip supports
it. However, as synchronous mode isn't supported by the hardware used
for testing (SainSmart 8-channel USB relay card) and is not as
straightforward to use (reading the inputs requires the outputs to be
written first) it's left as a potential future enhancement.

Serial mode and GPIO mode were tested on FT232RL using a simple
loopback setup (TXD connected to RXD). In addition, GPIO output mode
was tested on FT245RL (8 channels).

Signed-off-by: Sascha Silbe <x-linux@xxxxxxxxxxxxxx>
---
Is making the GPIO support conditional on CONFIG_GPIOLIB enough or
should I introduce a new configuration option USB_SERIAL_FTDI_SIO_GPIO
that depends on CONFIG_GPIOLIB?

Signed-off-by: Sascha Silbe <x-linux@xxxxxxxxxxxxxx>
---
 drivers/usb/serial/ftdi_sio.c | 264 +++++++++++++++++++++++++++++++++++++++++-
 drivers/usb/serial/ftdi_sio.h |  26 +++++
 2 files changed, 289 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index edf3b12..92f5c14 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -33,6 +33,9 @@
 
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#ifdef CONFIG_GPIOLIB
+#include <linux/gpio.h>
+#endif
 #include <linux/slab.h>
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
@@ -53,6 +56,7 @@
 
 struct ftdi_private {
 	enum ftdi_chip_type chip_type;
+	struct usb_serial_port *port;
 				/* type of device, either SIO or FT8U232AM */
 	int baud_base;		/* baud base clock for divisor setting */
 	int custom_divisor;	/* custom_divisor kludge, this is for
@@ -77,6 +81,15 @@ 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() */
+#ifdef CONFIG_GPIOLIB
+	struct gpio_chip gc;
+	bool serial_open;
+	unsigned char open_gpios;
+	unsigned int bitmode;
+	unsigned char gpio_direction; /* data direction in bitbang
+				       * mode, 0=in / 1=out */
+	unsigned char gpo_values; /* GPIO output values */
+#endif
 };
 
 /* struct ftdi_sio_quirk is used by devices requiring special attention. */
@@ -973,6 +986,7 @@ static int  ftdi_sio_probe(struct usb_serial *serial,
 static int  ftdi_sio_port_probe(struct usb_serial_port *port);
 static int  ftdi_sio_port_remove(struct usb_serial_port *port);
 static int  ftdi_open(struct tty_struct *tty, struct usb_serial_port *port);
+static void ftdi_close(struct usb_serial_port *port);
 static void ftdi_dtr_rts(struct usb_serial_port *port, int on);
 static void ftdi_process_read_urb(struct urb *urb);
 static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
@@ -996,6 +1010,15 @@ static __u32 ftdi_232bm_baud_to_divisor(int baud);
 static __u32 ftdi_2232h_baud_base_to_divisor(int baud, int base);
 static __u32 ftdi_2232h_baud_to_divisor(int baud);
 
+#ifdef CONFIG_GPIOLIB
+static int ftdi_gpio_get(struct gpio_chip *gc, unsigned int gpio);
+static void ftdi_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val);
+static int ftdi_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio);
+static int ftdi_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val);
+static int ftdi_gpio_request(struct gpio_chip *chip, unsigned offset);
+static void ftdi_gpio_free(struct gpio_chip *chip, unsigned offset);
+#endif
+
 static struct usb_serial_driver ftdi_sio_device = {
 	.driver = {
 		.owner =	THIS_MODULE,
@@ -1010,6 +1033,7 @@ static struct usb_serial_driver ftdi_sio_device = {
 	.port_probe =		ftdi_sio_port_probe,
 	.port_remove =		ftdi_sio_port_remove,
 	.open =			ftdi_open,
+	.close =			ftdi_close,
 	.dtr_rts =		ftdi_dtr_rts,
 	.throttle =		usb_serial_generic_throttle,
 	.unthrottle =		usb_serial_generic_unthrottle,
@@ -1379,6 +1403,59 @@ static int read_latency_timer(struct usb_serial_port *port)
 	return rv;
 }
 
+#ifdef CONFIG_GPIOLIB
+static int write_bitmode(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_device *udev = port->serial->dev;
+	int rv;
+	int bitmode = priv->bitmode;
+	int gpio_direction = priv->gpio_direction;
+
+	dev_dbg(&port->dev, "%s: setting bitmode = %i, direction = %i\n",
+		__func__, bitmode, gpio_direction);
+
+	rv = usb_control_msg(udev,
+			     usb_sndctrlpipe(udev, 0),
+			     FTDI_SIO_SET_BITMODE_REQUEST,
+			     FTDI_SIO_SET_BITMODE_REQUEST_TYPE,
+			     gpio_direction | bitmode, priv->interface,
+			     NULL, 0, WDR_TIMEOUT);
+	if (rv < 0)
+		dev_err(&port->dev, "Unable to write bitmode: %i\n", rv);
+	return rv;
+}
+
+/*
+ * Returns the GPIO pin values, or negative error code.
+ */
+static int read_pins(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_device *udev = port->serial->dev;
+	unsigned char *buf;
+	unsigned char pin_states;
+	int rv;
+
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	rv = usb_control_msg(udev,
+			     usb_rcvctrlpipe(udev, 0),
+			     FTDI_SIO_READ_PINS_REQUEST,
+			     FTDI_SIO_READ_PINS_REQUEST_TYPE,
+			     0, priv->interface,
+			     buf, 1, WDR_TIMEOUT);
+	if (rv < 0)
+		dev_err(&port->dev, "Unable to read pins: %i\n", rv);
+
+	pin_states = buf[0];
+	kfree(buf);
+	return (rv < 0) ? rv : pin_states;
+}
+#endif
+
 static int get_serial_info(struct usb_serial_port *port,
 				struct serial_struct __user *retinfo)
 {
@@ -1731,7 +1808,7 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv;
 	struct ftdi_sio_quirk *quirk = usb_get_serial_data(port->serial);
-
+	int error;
 
 	priv = kzalloc(sizeof(struct ftdi_private), GFP_KERNEL);
 	if (!priv)
@@ -1752,6 +1829,57 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 		priv->latency = 16;
 	write_latency_timer(port);
 	create_sysfs_attrs(port);
+
+#ifdef CONFIG_GPIOLIB
+	priv->serial_open = false;
+	priv->gpo_values = 0;
+	priv->gpio_direction = 0;
+	priv->open_gpios = 0;
+	priv->port = port;
+	priv->gc.owner = THIS_MODULE;
+	priv->gc.direction_input = ftdi_gpio_dir_in;
+	priv->gc.direction_output = ftdi_gpio_dir_out;
+	priv->gc.get = ftdi_gpio_get;
+	priv->gc.set = ftdi_gpio_set;
+	priv->gc.request = ftdi_gpio_request;
+	priv->gc.free = ftdi_gpio_free;
+	priv->gc.can_sleep = true;
+	priv->gc.base = -1;
+	switch (priv->chip_type) {
+	case SIO:
+	case FT8U232AM:
+		priv->gc.ngpio = 0;
+		break;
+	case FT232BM:
+	case FT2232C:
+	case FT232RL:
+	case FT2232H:
+	case FT4232H:
+	case FT232H:
+		priv->gc.ngpio = 8;
+		break;
+	case FTX:
+		/* 8 on FT231X and FT240X, but only 4 on FT230X and
+		 * FT234XD. We don't know of any way to distinguish
+		 * these chips, so we use the higher value. */
+		priv->gc.ngpio = 8;
+		break;
+	}
+	priv->gc.dev = &port->dev;
+	priv->gc.label = dev_name(&port->dev);
+
+	dev_dbg(&port->dev, "ngpio=%d\n", priv->gc.ngpio);
+	if (!priv->gc.ngpio)
+		return 0;
+
+	error = gpiochip_add(&priv->gc);
+	if (error) {
+		dev_err(&port->dev, "ftdi_sio: Failed to register GPIOs\n");
+		/* We can still use it as a serial port. Just mark the
+		 * GPIOs as unused for ftdi_sio_port_remove(). */
+		priv->gc.ngpio = 0;
+	}
+#endif
 	return 0;
 }
 
@@ -1881,7 +2009,15 @@ static int ftdi_mtxorb_hack_setup(struct usb_serial *serial)
 static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	int error;
 
+#ifdef CONFIG_GPIOLIB
+	if (priv->gc.ngpio) {
+		error = gpiochip_remove(&priv->gc);
+		if (error)
+			return error;
+	}
+#endif
 	remove_sysfs_attrs(port);
 
 	kfree(priv);
@@ -1893,6 +2029,19 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct usb_device *dev = port->serial->dev;
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	int error;
+
+#ifdef CONFIG_GPIOLIB
+	if (priv->open_gpios)
+		return -ENXIO;
+
+	mutex_lock(&priv->cfg_lock);
+	priv->bitmode = FTDI_SIO_SET_BITMODE_RESET;
+	error = write_bitmode(port);
+	mutex_unlock(&priv->cfg_lock);
+	if (error)
+		return -EIO;
+#endif
 
 	/* No error checking for this (will get errors later anyway) */
 	/* See ftdi_sio.h for description of what is reset */
@@ -1909,9 +2058,20 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 	if (tty)
 		ftdi_set_termios(tty, port, NULL);
 
+#ifdef CONFIG_GPIOLIB
+	priv->serial_open = true;
+#endif
 	return usb_serial_generic_open(tty, port);
 }
 
+static void ftdi_close(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+
+	priv->serial_open = false;
+	usb_serial_generic_close(port);
+}
+
 static void ftdi_dtr_rts(struct usb_serial_port *port, int on)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
@@ -2452,6 +2612,108 @@ static int ftdi_ioctl(struct tty_struct *tty,
 	return -ENOIOCTLCMD;
 }
 
+#ifdef CONFIG_GPIOLIB
+static inline struct ftdi_private *gc_to_ftdi_private(struct gpio_chip *gc)
+{
+	return container_of(gc, struct ftdi_private, gc);
+}
+
+static int ftdi_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+	int value = read_pins(priv->port);
+	dev_dbg(&port->dev, "%s - value=%d\n", __func__, value);
+	if (value < 0)
+		return value;
+	return (value & (1 << gpio)) ? 1 : 0;
+}
+
+static void ftdi_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+	struct tty_struct *tty = tty_port_tty_get(&port->port);
+	struct device *dev = &port->dev;
+	int sent;
+
+	mutex_lock(&priv->cfg_lock);
+	if (val)
+		priv->gpo_values |= 1 << gpio;
+	else
+		priv->gpo_values &= ~(1 << gpio);
+	dev_dbg(dev, "%s - gpo_values=%d\n", __func__, priv->gpo_values);
+	sent = port->serial->type->write(tty, port, &(priv->gpo_values), 1);
+	mutex_unlock(&priv->cfg_lock);
+	if (sent < 1)
+		dev_err(dev, "error %d setting outputs (ignored)\n", sent);
+}
+
+static int ftdi_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+	struct device *dev = &port->dev;
+	int error;
+
+	mutex_lock(&priv->cfg_lock);
+	priv->gpio_direction &= ~(1 << gpio);
+	dev_dbg(dev, "%s - direction=%d\n", __func__, priv->gpio_direction);
+	error = write_bitmode(priv->port);
+	mutex_unlock(&priv->cfg_lock);
+	dev_dbg(dev, "%s - error=%d\n", __func__, error);
+	return error ? -EIO : 0;
+}
+
+static int ftdi_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+	struct device *dev = &port->dev;
+	int error;
+
+	gc->set(gc, gpio, val);
+	mutex_lock(&priv->cfg_lock);
+	priv->gpio_direction |= (1 << gpio);
+	dev_dbg(dev, "%s - direction=%d\n", __func__, priv->gpio_direction);
+	error = write_bitmode(priv->port);
+	mutex_unlock(&priv->cfg_lock);
+	dev_dbg(dev, "%s - error=%d\n", __func__, error);
+	return error ? -EIO : 0;
+}
+
+static int ftdi_gpio_request(struct gpio_chip *gc, unsigned offset)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+	int error;
+
+	if (priv->serial_open)
+		return -ENXIO;
+
+	mutex_lock(&priv->cfg_lock);
+	priv->bitmode = FTDI_SIO_SET_BITMODE_BITBANG;
+	error = write_bitmode(priv->port);
+	if (!error)
+		priv->open_gpios |= 1 << offset;
+	dev_dbg(&port->dev, "%s - open_gpios=%d\n", __func__, priv->open_gpios);
+	mutex_unlock(&priv->cfg_lock);
+	dev_dbg(&port->dev, "%s - error=%d\n", __func__, error);
+	return error ? -EIO : 0;
+}
+
+static void ftdi_gpio_free(struct gpio_chip *gc, unsigned offset)
+{
+	struct ftdi_private *priv = gc_to_ftdi_private(gc);
+	struct usb_serial_port *port = priv->port;
+
+	mutex_lock(&priv->cfg_lock);
+	priv->open_gpios &= ~(1 << offset);
+	dev_dbg(&port->dev, "%s - open_gpios=%d\n", __func__, priv->open_gpios);
+	mutex_unlock(&priv->cfg_lock);
+}
+#endif
+
 module_usb_serial_driver(serial_drivers, id_table_combined);
 
 MODULE_AUTHOR(DRIVER_AUTHOR);
diff --git a/drivers/usb/serial/ftdi_sio.h b/drivers/usb/serial/ftdi_sio.h
index ed58c6f..53ea96d 100644
--- a/drivers/usb/serial/ftdi_sio.h
+++ b/drivers/usb/serial/ftdi_sio.h
@@ -35,6 +35,8 @@
 #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 transfer mode */
+#define FTDI_SIO_READ_PINS		12 /* Read pin values in GPIO mode */
 
 /* Interface indices for FT2232, FT2232H and FT4232H devices */
 #define INTERFACE_A		1
@@ -345,6 +347,30 @@ enum ftdi_sio_baudrate {
  */
 
 /*
+ * FTDI_SIO_SET_BITMODE
+ */
+#define FTDI_SIO_SET_BITMODE_REQUEST FTDI_SIO_SET_BITMODE
+#define FTDI_SIO_SET_BITMODE_REQUEST_TYPE 0x40
+
+#define FTDI_SIO_SET_BITMODE_MASK 0x4F
+#define FTDI_SIO_SET_BITMODE_RESET (0x00 << 8)
+#define FTDI_SIO_SET_BITMODE_BITBANG (0x01 << 8)
+#define FTDI_SIO_SET_BITMODE_MPSSE (0x02 << 8)
+#define FTDI_SIO_SET_BITMODE_SYNCBB (0x04 << 8)
+#define FTDI_SIO_SET_BITMODE_MCU (0x08 << 8)
+#define FTDI_SIO_SET_BITMODE_OPTO (0x10 << 8)
+#define FTDI_SIO_SET_BITMODE_CBUS (0x20 << 8)
+#define FTDI_SIO_SET_BITMODE_SYNCFF (0x40 << 8)
+
+/*
+ * FTDI_SIO_READ_PINS
+ *
+ * Read the GPIO pin values without any buffering.
+ */
+#define  FTDI_SIO_READ_PINS_REQUEST FTDI_SIO_READ_PINS
+#define  FTDI_SIO_READ_PINS_REQUEST_TYPE 0xC0
+
+/*
  * FTDI_SIO_SET_EVENT_CHAR
  *
  * Set the special event character for the specified communications port.
-- 
1.9.1

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