USB: usb-serial ch341: support for DTR/RTS/CTS

commit 664d5df9 upstream.

Fixup of Werner Cornelius patch to the ch341 USB-serial driver, which adds:
- support all baudrates, not just a hard-coded set
- support for controlling DTR, RTS and CTS

Features still missing:
- character length other than 8 bits
- parity settings
- break control

I adapted his patch for the new usb_serial API introduced in 2.6.25-git8 by
Alan Cox on 22 July 2008. Non-compliance to the new API was a reason for
refusing a similar patch from Tollef Fog Heen.

Usage example by Tollef Fog Heen :
        TEMPer USB thermometer <http://err.no/src/TEMPer.c>

based on a patch by:

	From: Tollef Fog Heen <tfheen@err.no>

	* Implement support for all baud rates rather than just a hard
	  coded set.
	* Make it possible to control status and control lines
	* Grab a bunch of #defines from FreeBSD to reduce the number of
	  magic numbers in the file
Signed-off-by: Werner Cornelius <Werner.Cornelius@cornelius-consult.de>
Signed-off-by: Boris Hajduk <boris@hajduk.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Tollef Fog Heen <tfheen@err.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ch341.c

 /*
  * Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
+ * Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
+ * Copyright 2009, Boris Hajduk <boris@hajduk.org>
  *
  * ch341.c implements a serial port driver for the Winchiphead CH341.
  *
@@ -21,9 +23,39 @@
 #include <linux/usb/serial.h>
 #include <linux/serial.h>
 
-#define DEFAULT_BAUD_RATE 2400
+#define DEFAULT_BAUD_RATE 9600
 #define DEFAULT_TIMEOUT   1000
 
+/* flags for IO-Bits */
+#define CH341_BIT_RTS (1 << 6)
+#define CH341_BIT_DTR (1 << 5)
+
+/******************************/
+/* interrupt pipe definitions */
+/******************************/
+/* always 4 interrupt bytes */
+/* first irq byte normally 0x08 */
+/* second irq byte base 0x7d + below */
+/* third irq byte base 0x94 + below */
+/* fourth irq byte normally 0xee */
+
+/* second interrupt byte */
+#define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
+
+/* status returned in third interrupt answer byte, inverted in data
+   from irq */
+#define CH341_BIT_CTS 0x01
+#define CH341_BIT_DSR 0x02
+#define CH341_BIT_RI  0x04
+#define CH341_BIT_DCD 0x08
+#define CH341_BITS_MODEM_STAT 0x0f /* all bits */
+
+/*******************************/
+/* baudrate calculation factor */
+/*******************************/
+#define CH341_BAUDBASE_FACTOR 1532620800
+#define CH341_BAUDBASE_DIVMAX 3
+
 static int debug;
 
 static struct usb_device_id id_table [] = {
@@ -34,9 +66,12 @@ static struct usb_device_id id_table [] = {
 MODULE_DEVICE_TABLE(usb, id_table);
 
 struct ch341_private {
-	unsigned baud_rate;
-	u8 dtr;
-	u8 rts;
+	spinlock_t lock; /* access lock */
+	wait_queue_head_t delta_msr_wait; /* wait queue for modem status */
+	unsigned baud_rate; /* set baud rate */
+	u8 line_control; /* set line control value RTS/DTR */
+	u8 line_status; /* active status of modem control inputs */
+	u8 multi_status_change; /* status changed multiple since last call */
 };
 
 static int ch341_control_out(struct usb_device *dev, u8 request,
@@ -72,37 +107,28 @@ static int ch341_set_baudrate(struct usb_device *dev,
 {
 	short a, b;
 	int r;
+	unsigned long factor;
+	short divisor;
 
 	dbg("ch341_set_baudrate(%d)", priv->baud_rate);
-	switch (priv->baud_rate) {
-	case 2400:
-		a = 0xd901;
-		b = 0x0038;
-		break;
-	case 4800:
-		a = 0x6402;
-		b = 0x001f;
-		break;
-	case 9600:
-		a = 0xb202;
-		b = 0x0013;
-		break;
-	case 19200:
-		a = 0xd902;
-		b = 0x000d;
-		break;
-	case 38400:
-		a = 0x6403;
-		b = 0x000a;
-		break;
-	case 115200:
-		a = 0xcc03;
-		b = 0x0008;
-		break;
-	default:
+
+	if (!priv->baud_rate)
 		return -EINVAL;
+	factor = (CH341_BAUDBASE_FACTOR / priv->baud_rate);
+	divisor = CH341_BAUDBASE_DIVMAX;
+
+	while ((factor > 0xfff0) && divisor) {
+		factor >>= 3;
+		divisor--;
 	}
 
+	if (factor > 0xfff0)
+		return -EINVAL;
+
+	factor = 0x10000 - factor;
+	a = (factor & 0xff00) | divisor;
+	b = factor & 0xff;
+
 	r = ch341_control_out(dev, 0x9a, 0x1312, a);
 	if (!r)
 		r = ch341_control_out(dev, 0x9a, 0x0f2c, b);
@@ -110,19 +136,18 @@ static int ch341_set_baudrate(struct usb_device *dev,
 	return r;
 }
 
-static int ch341_set_handshake(struct usb_device *dev,
-			       struct ch341_private *priv)
+static int ch341_set_handshake(struct usb_device *dev, u8 control)
 {
-	dbg("ch341_set_handshake(%d,%d)", priv->dtr, priv->rts);
-	return ch341_control_out(dev, 0xa4,
-		~((priv->dtr?1<<5:0)|(priv->rts?1<<6:0)), 0);
+	dbg("ch341_set_handshake(0x%02x)", control);
+	return ch341_control_out(dev, 0xa4, ~control, 0);
 }
 
-static int ch341_get_status(struct usb_device *dev)
+static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
 {
 	char *buffer;
 	int r;
 	const unsigned size = 8;
+	unsigned long flags;
 
 	dbg("ch341_get_status()");
 
@@ -134,10 +159,15 @@ static int ch341_get_status(struct usb_device *dev)
 	if (r < 0)
 		goto out;
 
-	/* Not having the datasheet for the CH341, we ignore the bytes returned
-	 * from the device. Return error if the device did not respond in time.
-	 */
-	r = 0;
+	/* setup the private status if available */
+	if (r == 2) {
+		r = 0;
+		spin_lock_irqsave(&priv->lock, flags);
+		priv->line_status = (~(*buffer)) & CH341_BITS_MODEM_STAT;
+		priv->multi_status_change = 0;
+		spin_unlock_irqrestore(&priv->lock, flags);
+	} else
+		r = -EPROTO;
 
 out:	kfree(buffer);
 	return r;
@@ -180,7 +210,7 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 		goto out;
 
 	/* expect 0xff 0xee */
-	r = ch341_get_status(dev);
+	r = ch341_get_status(dev, priv);
 	if (r < 0)
 		goto out;
 
@@ -192,12 +222,12 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 	if (r < 0)
 		goto out;
 
-	r = ch341_set_handshake(dev, priv);
+	r = ch341_set_handshake(dev, priv->line_control);
 	if (r < 0)
 		goto out;
 
 	/* expect 0x9f 0xee */
-	r = ch341_get_status(dev);
+	r = ch341_get_status(dev, priv);
 
 out:	kfree(buffer);
 	return r;
@@ -216,9 +246,10 @@ static int ch341_attach(struct usb_serial *serial)
 	if (!priv)
 		return -ENOMEM;
 
+	spin_lock_init(&priv->lock);
+	init_waitqueue_head(&priv->delta_msr_wait);
 	priv->baud_rate = DEFAULT_BAUD_RATE;
-	priv->dtr = 1;
-	priv->rts = 1;
+	priv->line_control = CH341_BIT_RTS | CH341_BIT_DTR;
 
 	r = ch341_configure(serial->dev, priv);
 	if (r < 0)
@@ -231,6 +262,35 @@ error:	kfree(priv);
 	return r;
 }
 
+static void ch341_close(struct tty_struct *tty, struct usb_serial_port *port,
+				struct file *filp)
+{
+	struct ch341_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	unsigned int c_cflag;
+
+	dbg("%s - port %d", __func__, port->number);
+
+	/* shutdown our urbs */
+	dbg("%s - shutting down urbs", __func__);
+	usb_kill_urb(port->write_urb);
+	usb_kill_urb(port->read_urb);
+	usb_kill_urb(port->interrupt_in_urb);
+
+	if (tty) {
+		c_cflag = tty->termios->c_cflag;
+		if (c_cflag & HUPCL) {
+			/* drop DTR and RTS */
+			spin_lock_irqsave(&priv->lock, flags);
+			priv->line_control = 0;
+			spin_unlock_irqrestore(&priv->lock, flags);
+			ch341_set_handshake(port->serial->dev, 0);
+		}
+	}
+	wake_up_interruptible(&priv->delta_msr_wait);
+}
+
+
 /* open this device, set default parameters */
 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port,
 				struct file *filp)
@@ -242,14 +302,13 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port,
 	dbg("ch341_open()");
 
 	priv->baud_rate = DEFAULT_BAUD_RATE;
-	priv->dtr = 1;
-	priv->rts = 1;
+	priv->line_control = CH341_BIT_RTS | CH341_BIT_DTR;
 
 	r = ch341_configure(serial->dev, priv);
 	if (r)
 		goto out;
 
-	r = ch341_set_handshake(serial->dev, priv);
+	r = ch341_set_handshake(serial->dev, priv->line_control);
 	if (r)
 		goto out;
 
@@ -257,6 +316,16 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port,
 	if (r)
 		goto out;
 
+	dbg("%s - submitting interrupt urb", __func__);
+	port->interrupt_in_urb->dev = serial->dev;
+	r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+	if (r) {
+		dev_err(&port->dev, "%s - failed submitting interrupt urb,"
+			" error %d\n", __func__, r);
+		ch341_close(tty, port, NULL);
+		return -EPROTO;
+	}
+
 	r = usb_serial_generic_open(tty, port, filp);
 
 out:	return r;
@@ -270,38 +339,194 @@ static void ch341_set_termios(struct tty_struct *tty,
 {
 	struct ch341_private *priv = usb_get_serial_port_data(port);
 	unsigned baud_rate;
+	unsigned long flags;
 
 	dbg("ch341_set_termios()");
 
+	if (!tty || !tty->termios)
+		return;
+
 	baud_rate = tty_get_baud_rate(tty);
 
-	switch (baud_rate) {
-	case 2400:
-	case 4800:
-	case 9600:
-	case 19200:
-	case 38400:
-	case 115200:
-		priv->baud_rate = baud_rate;
-		break;
-	default:
-		dbg("Rate %d not supported, using %d",
-			baud_rate, DEFAULT_BAUD_RATE);
-		priv->baud_rate = DEFAULT_BAUD_RATE;
+	priv->baud_rate = baud_rate;
+
+	if (baud_rate) {
+		spin_lock_irqsave(&priv->lock, flags);
+		priv->line_control |= (CH341_BIT_DTR | CH341_BIT_RTS);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		ch341_set_baudrate(port->serial->dev, priv);
+	} else {
+		spin_lock_irqsave(&priv->lock, flags);
+		priv->line_control &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
+		spin_unlock_irqrestore(&priv->lock, flags);
 	}
 
-	ch341_set_baudrate(port->serial->dev, priv);
+	ch341_set_handshake(port->serial->dev, priv->line_control);
 
 	/* Unimplemented:
 	 * (cflag & CSIZE) : data bits [5, 8]
 	 * (cflag & PARENB) : parity {NONE, EVEN, ODD}
 	 * (cflag & CSTOPB) : stop bits [1, 2]
 	 */
+}
+
+static int ch341_tiocmset(struct tty_struct *tty, struct file *file,
+			  unsigned int set, unsigned int clear)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct ch341_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	u8 control;
+
+	spin_lock_irqsave(&priv->lock, flags);
+	if (set & TIOCM_RTS)
+		priv->line_control |= CH341_BIT_RTS;
+	if (set & TIOCM_DTR)
+		priv->line_control |= CH341_BIT_DTR;
+	if (clear & TIOCM_RTS)
+		priv->line_control &= ~CH341_BIT_RTS;
+	if (clear & TIOCM_DTR)
+		priv->line_control &= ~CH341_BIT_DTR;
+	control = priv->line_control;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return ch341_set_handshake(port->serial->dev, control);
+}
+
+static void ch341_read_int_callback(struct urb *urb)
+{
+	struct usb_serial_port *port = (struct usb_serial_port *) urb->context;
+	unsigned char *data = urb->transfer_buffer;
+	unsigned int actual_length = urb->actual_length;
+	int status;
+
+	dbg("%s (%d)", __func__, port->number);
+
+	switch (urb->status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dbg("%s - urb shutting down with status: %d", __func__,
+		    urb->status);
+		return;
+	default:
+		dbg("%s - nonzero urb status received: %d", __func__,
+		    urb->status);
+		goto exit;
+	}
+
+	usb_serial_debug_data(debug, &port->dev, __func__,
+			      urb->actual_length, urb->transfer_buffer);
+
+	if (actual_length >= 4) {
+		struct ch341_private *priv = usb_get_serial_port_data(port);
+		unsigned long flags;
+
+		spin_lock_irqsave(&priv->lock, flags);
+		priv->line_status = (~(data[2])) & CH341_BITS_MODEM_STAT;
+		if ((data[1] & CH341_MULT_STAT))
+			priv->multi_status_change = 1;
+		spin_unlock_irqrestore(&priv->lock, flags);
+		wake_up_interruptible(&priv->delta_msr_wait);
+	}
+
+exit:
+	status = usb_submit_urb(urb, GFP_ATOMIC);
+	if (status)
+		dev_err(&urb->dev->dev,
+			"%s - usb_submit_urb failed with result %d\n",
+			__func__, status);
+}
+
+static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
+{
+	struct ch341_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	u8 prevstatus;
+	u8 status;
+	u8 changed;
+	u8 multi_change = 0;
+
+	spin_lock_irqsave(&priv->lock, flags);
+	prevstatus = priv->line_status;
+	priv->multi_status_change = 0;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	while (!multi_change) {
+		interruptible_sleep_on(&priv->delta_msr_wait);
+		/* see if a signal did it */
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+
+		spin_lock_irqsave(&priv->lock, flags);
+		status = priv->line_status;
+		multi_change = priv->multi_status_change;
+		spin_unlock_irqrestore(&priv->lock, flags);
+
+		changed = prevstatus ^ status;
+
+		if (((arg & TIOCM_RNG) && (changed & CH341_BIT_RI)) ||
+		    ((arg & TIOCM_DSR) && (changed & CH341_BIT_DSR)) ||
+		    ((arg & TIOCM_CD)  && (changed & CH341_BIT_DCD)) ||
+		    ((arg & TIOCM_CTS) && (changed & CH341_BIT_CTS))) {
+			return 0;
+		}
+		prevstatus = status;
+	}
+
+	return 0;
+}
+
+/*static int ch341_ioctl(struct usb_serial_port *port, struct file *file,*/
+static int ch341_ioctl(struct tty_struct *tty, struct file *file,
+			unsigned int cmd, unsigned long arg)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	dbg("%s (%d) cmd = 0x%04x", __func__, port->number, cmd);
+
+	switch (cmd) {
+	case TIOCMIWAIT:
+		dbg("%s (%d) TIOCMIWAIT", __func__,  port->number);
+		return wait_modem_info(port, arg);
+
+	default:
+		dbg("%s not supported = 0x%04x", __func__, cmd);
+		break;
+	}
+
+	return -ENOIOCTLCMD;
+}
+
+static int ch341_tiocmget(struct tty_struct *tty, struct file *file)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct ch341_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	u8 mcr;
+	u8 status;
+	unsigned int result;
+
+	dbg("%s (%d)", __func__, port->number);
+
+	spin_lock_irqsave(&priv->lock, flags);
+	mcr = priv->line_control;
+	status = priv->line_status;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	result = ((mcr & CH341_BIT_DTR)		? TIOCM_DTR : 0)
+		  | ((mcr & CH341_BIT_RTS)	? TIOCM_RTS : 0)
+		  | ((status & CH341_BIT_CTS)	? TIOCM_CTS : 0)
+		  | ((status & CH341_BIT_DSR)	? TIOCM_DSR : 0)
+		  | ((status & CH341_BIT_RI)	? TIOCM_RI  : 0)
+		  | ((status & CH341_BIT_DCD)	? TIOCM_CD  : 0);
+
+	dbg("%s - result = %x", __func__, result);
 
-	 /* Copy back the old hardware settings */
-	 tty_termios_copy_hw(tty->termios, old_termios);
-	 /* And re-encode with the new baud */
-	 tty_encode_baud_rate(tty, baud_rate, baud_rate);
+	return result;
 }
 
 
@@ -339,12 +564,17 @@ static struct usb_serial_driver ch341_device = {
 		.owner	= THIS_MODULE,
 		.name	= "ch341-uart",
 	},
-	.id_table         = id_table,
-	.usb_driver       = &ch341_driver,
-	.num_ports        = 1,
-	.open             = ch341_open,
-	.set_termios      = ch341_set_termios,
-	.attach           = ch341_attach,
+	.id_table          = id_table,
+	.usb_driver        = &ch341_driver,
+	.num_ports         = 1,
+	.open              = ch341_open,
+	.close             = ch341_close,
+	.ioctl             = ch341_ioctl,
+	.set_termios       = ch341_set_termios,
+	.tiocmget          = ch341_tiocmget,
+	.tiocmset          = ch341_tiocmset,
+	.read_int_callback = ch341_read_int_callback,
+	.attach            = ch341_attach,
 };
 
 static int __init ch341_init(void)