Merge tag 'usb-serial-5.11-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial into usb-next

Johan writes:

USB-serial updates for 5.11-rc1

Here are the USB-serial updates for 5.11-rc1, including:

 - keyspan_pda write-implementation fixes
 - digi_acceleport write-wakeup fix
 - mos7720 parport-restore fix
 - mos7720 parport-tasklet removal
 - cp210x termios-handling cleanups
 - option device-flag fix
 - ftdi_sio GPIO CBUS-configuration improvements
 - removal of in_interrupt() uses

Included are also various clean ups.

All have been in linux-next with no reported issues.

* tag 'usb-serial-5.11-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial: (30 commits)
  USB: serial: ftdi_sio: log the CBUS GPIO validity
  USB: serial: ftdi_sio: drop GPIO line checking dead code
  USB: serial: ftdi_sio: report the valid GPIO lines to gpiolib
  USB: serial: option: add interface-number sanity check to flag handling
  USB: serial: cp210x: clean up dtr_rts()
  USB: serial: cp210x: refactor flow-control handling
  USB: serial: cp210x: drop flow-control debugging
  USB: serial: cp210x: set terminal settings on open
  USB: serial: cp210x: clean up line-control handling
  USB: serial: cp210x: return early on unchanged termios
  USB: serial: mos7720: defer state restore to a workqueue
  USB: serial: mos7720: fix parallel-port state restore
  USB: serial: remove write wait queue
  USB: serial: digi_acceleport: fix write-wakeup deadlocks
  USB: serial: keyspan_pda: drop redundant usb-serial pointer
  USB: serial: keyspan_pda: use BIT() macro
  USB: serial: keyspan_pda: clean up comments and whitespace
  USB: serial: keyspan_pda: clean up xircom/entrega support
  USB: serial: keyspan_pda: add write-fifo support
  USB: serial: keyspan_pda: increase transmitter threshold
  ...

18 files changed, 444 insertions, 979 deletions

diff --git a/arch/arm/configs/badge4_defconfig b/arch/arm/configs/badge4_defconfig
index ef484c4cfd1a..d9119da65f48 100644
--- a/arch/arm/configs/badge4_defconfig
+++ b/arch/arm/configs/badge4_defconfig
@@ -89,7 +89,6 @@ CONFIG_USB_SERIAL_KEYSPAN=m
 CONFIG_USB_SERIAL_MCT_U232=m
 CONFIG_USB_SERIAL_PL2303=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_EXT2_FS=m
 CONFIG_EXT3_FS=m
diff --git a/arch/arm/configs/corgi_defconfig b/arch/arm/configs/corgi_defconfig
index 4fec2ec379ad..911e880f06ed 100644
--- a/arch/arm/configs/corgi_defconfig
+++ b/arch/arm/configs/corgi_defconfig
@@ -191,7 +191,6 @@ CONFIG_USB_SERIAL_PL2303=m
 CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_EMI62=m
 CONFIG_USB_EMI26=m
diff --git a/arch/arm/configs/pxa_defconfig b/arch/arm/configs/pxa_defconfig
index d7b9eaf4783c..8654ece13004 100644
--- a/arch/arm/configs/pxa_defconfig
+++ b/arch/arm/configs/pxa_defconfig
@@ -574,7 +574,6 @@ CONFIG_USB_SERIAL_PL2303=m
 CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_EMI62=m
 CONFIG_USB_EMI26=m
diff --git a/arch/arm/configs/spitz_defconfig b/arch/arm/configs/spitz_defconfig
index a1cdbfa064c5..8b2c14424927 100644
--- a/arch/arm/configs/spitz_defconfig
+++ b/arch/arm/configs/spitz_defconfig
@@ -185,7 +185,6 @@ CONFIG_USB_SERIAL_PL2303=m
 CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_EMI62=m
 CONFIG_USB_EMI26=m
diff --git a/arch/mips/configs/mtx1_defconfig b/arch/mips/configs/mtx1_defconfig
index 914af125a7fa..9750bcc38f05 100644
--- a/arch/mips/configs/mtx1_defconfig
+++ b/arch/mips/configs/mtx1_defconfig
@@ -565,7 +565,6 @@ CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_SIERRAWIRELESS=m
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OPTION=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_EMI62=m
diff --git a/arch/mips/configs/rm200_defconfig b/arch/mips/configs/rm200_defconfig
index 30d7c3db884e..3dc2da2bee0d 100644
--- a/arch/mips/configs/rm200_defconfig
+++ b/arch/mips/configs/rm200_defconfig
@@ -311,7 +311,6 @@ CONFIG_USB_SERIAL_PL2303=m
 CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_SAFE_PADDED=y
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_LEGOTOWER=m
 CONFIG_USB_LCD=m
diff --git a/arch/powerpc/configs/g5_defconfig b/arch/powerpc/configs/g5_defconfig
index 1c674c4c1d86..1de0dbf6cbba 100644
--- a/arch/powerpc/configs/g5_defconfig
+++ b/arch/powerpc/configs/g5_defconfig
@@ -194,7 +194,6 @@ CONFIG_USB_SERIAL_SAFE=m
 CONFIG_USB_SERIAL_SAFE_PADDED=y
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_APPLEDISPLAY=m
 CONFIG_EXT2_FS=y
diff --git a/arch/powerpc/configs/ppc6xx_defconfig b/arch/powerpc/configs/ppc6xx_defconfig
index 66e9a0fd64ff..ac92cbe1f581 100644
--- a/arch/powerpc/configs/ppc6xx_defconfig
+++ b/arch/powerpc/configs/ppc6xx_defconfig
@@ -911,7 +911,6 @@ CONFIG_USB_SERIAL_SAFE_PADDED=y
 CONFIG_USB_SERIAL_SIERRAWIRELESS=m
 CONFIG_USB_SERIAL_TI=m
 CONFIG_USB_SERIAL_CYBERJACK=m
-CONFIG_USB_SERIAL_XIRCOM=m
 CONFIG_USB_SERIAL_OPTION=m
 CONFIG_USB_SERIAL_OMNINET=m
 CONFIG_USB_SERIAL_DEBUG=m
diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index 4007fa25a8ff..a21ff5ab6df9 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -298,12 +298,12 @@ config USB_SERIAL_IUU
 	  module will be called iuu_phoenix.o
 
 config USB_SERIAL_KEYSPAN_PDA
-	tristate "USB Keyspan PDA Single Port Serial Driver"
+	tristate "USB Keyspan PDA / Xircom Single Port Serial Driver"
 	select USB_EZUSB_FX2
 	help
-	  Say Y here if you want to use a Keyspan PDA single port USB to
-	  serial converter device.  This driver makes use of firmware
-	  developed from scratch by Brian Warner.
+	  Say Y here if you want to use a Keyspan PDA, Xircom or Entrega single
+	  port USB to serial converter device. This driver makes use of
+	  firmware developed from scratch by Brian Warner.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called keyspan_pda.
@@ -538,17 +538,6 @@ config USB_SERIAL_CYBERJACK
 
 	  If unsure, say N.
 
-config USB_SERIAL_XIRCOM
-	tristate "USB Xircom / Entrega Single Port Serial Driver"
-	select USB_EZUSB_FX2
-	help
-	  Say Y here if you want to use a Xircom or Entrega single port USB to
-	  serial converter device.  This driver makes use of firmware
-	  developed from scratch by Brian Warner.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called keyspan_pda.
-
 config USB_SERIAL_WWAN
 	tristate
 
diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
index 2d491e434f11..50c53aed787a 100644
--- a/drivers/usb/serial/Makefile
+++ b/drivers/usb/serial/Makefile
@@ -61,5 +61,4 @@ obj-$(CONFIG_USB_SERIAL_UPD78F0730)		+= upd78f0730.o
 obj-$(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_XSENS_MT)		+= xsens_mt.o
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index d0c05aa8a0d6..fbb10dfc56e3 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -31,9 +31,6 @@
  */
 static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *);
 static void cp210x_close(struct usb_serial_port *);
-static void cp210x_get_termios(struct tty_struct *, struct usb_serial_port *);
-static void cp210x_get_termios_port(struct usb_serial_port *port,
-	tcflag_t *cflagp, unsigned int *baudp);
 static void cp210x_change_speed(struct tty_struct *, struct usb_serial_port *,
 							struct ktermios *);
 static void cp210x_set_termios(struct tty_struct *, struct usb_serial_port *,
@@ -49,7 +46,7 @@ static void cp210x_disconnect(struct usb_serial *);
 static void cp210x_release(struct usb_serial *);
 static int cp210x_port_probe(struct usb_serial_port *);
 static int cp210x_port_remove(struct usb_serial_port *);
-static void cp210x_dtr_rts(struct usb_serial_port *p, int on);
+static void cp210x_dtr_rts(struct usb_serial_port *port, int on);
 static void cp210x_process_read_urb(struct urb *urb);
 static void cp210x_enable_event_mode(struct usb_serial_port *port);
 static void cp210x_disable_event_mode(struct usb_serial_port *port);
@@ -267,7 +264,6 @@ enum cp210x_event_state {
 
 struct cp210x_port_private {
 	u8			bInterfaceNumber;
-	bool			has_swapped_line_ctl;
 	bool			event_mode;
 	enum cp210x_event_state event_state;
 	u8 lsr;
@@ -559,14 +555,8 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 	int result;
 
 	dmabuf = kmalloc(bufsize, GFP_KERNEL);
-	if (!dmabuf) {
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		memset(buf, 0, bufsize);
+	if (!dmabuf)
 		return -ENOMEM;
-	}
 
 	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
 			req, REQTYPE_INTERFACE_TO_HOST, 0,
@@ -580,12 +570,6 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 				req, bufsize, result);
 		if (result >= 0)
 			result = -EIO;
-
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		memset(buf, 0, bufsize);
 	}
 
 	kfree(dmabuf);
@@ -594,46 +578,6 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 }
 
 /*
- * Reads any 32-bit CP210X_ register identified by req.
- */
-static int cp210x_read_u32_reg(struct usb_serial_port *port, u8 req, u32 *val)
-{
-	__le32 le32_val;
-	int err;
-
-	err = cp210x_read_reg_block(port, req, &le32_val, sizeof(le32_val));
-	if (err) {
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		*val = 0;
-		return err;
-	}
-
-	*val = le32_to_cpu(le32_val);
-
-	return 0;
-}
-
-/*
- * Reads any 16-bit CP210X_ register identified by req.
- */
-static int cp210x_read_u16_reg(struct usb_serial_port *port, u8 req, u16 *val)
-{
-	__le16 le16_val;
-	int err;
-
-	err = cp210x_read_reg_block(port, req, &le16_val, sizeof(le16_val));
-	if (err)
-		return err;
-
-	*val = le16_to_cpu(le16_val);
-
-	return 0;
-}
-
-/*
  * Reads any 8-bit CP210X_ register identified by req.
  */
 static int cp210x_read_u8_reg(struct usb_serial_port *port, u8 req, u8 *val)
@@ -780,59 +724,6 @@ static int cp210x_write_vendor_block(struct usb_serial *serial, u8 type,
 }
 #endif
 
-/*
- * Detect CP2108 GET_LINE_CTL bug and activate workaround.
- * Write a known good value 0x800, read it back.
- * If it comes back swapped the bug is detected.
- * Preserve the original register value.
- */
-static int cp210x_detect_swapped_line_ctl(struct usb_serial_port *port)
-{
-	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
-	u16 line_ctl_save;
-	u16 line_ctl_test;
-	int err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_save);
-	if (err)
-		return err;
-
-	err = cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, 0x800);
-	if (err)
-		return err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_test);
-	if (err)
-		return err;
-
-	if (line_ctl_test == 8) {
-		port_priv->has_swapped_line_ctl = true;
-		line_ctl_save = swab16(line_ctl_save);
-	}
-
-	return cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, line_ctl_save);
-}
-
-/*
- * Must always be called instead of cp210x_read_u16_reg(CP210X_GET_LINE_CTL)
- * to workaround cp2108 bug and get correct value.
- */
-static int cp210x_get_line_ctl(struct usb_serial_port *port, u16 *ctl)
-{
-	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
-	int err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, ctl);
-	if (err)
-		return err;
-
-	/* Workaround swapped bytes in 16-bit value from CP210X_GET_LINE_CTL */
-	if (port_priv->has_swapped_line_ctl)
-		*ctl = swab16(*ctl);
-
-	return 0;
-}
-
 static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
@@ -844,16 +735,8 @@ static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
 		return result;
 	}
 
-	/* Configure the termios structure */
-	cp210x_get_termios(tty, port);
-
-	if (tty) {
-		/* The baud rate must be initialised on cp2104 */
-		cp210x_change_speed(tty, port, NULL);
-
-		if (I_INPCK(tty))
-			cp210x_enable_event_mode(port);
-	}
+	if (tty)
+		cp210x_set_termios(tty, port, NULL);
 
 	result = usb_serial_generic_open(tty, port);
 	if (result)
@@ -1032,167 +915,6 @@ static bool cp210x_tx_empty(struct usb_serial_port *port)
 	return !count;
 }
 
-/*
- * cp210x_get_termios
- * Reads the baud rate, data bits, parity, stop bits and flow control mode
- * from the device, corrects any unsupported values, and configures the
- * termios structure to reflect the state of the device
- */
-static void cp210x_get_termios(struct tty_struct *tty,
-	struct usb_serial_port *port)
-{
-	unsigned int baud;
-
-	if (tty) {
-		cp210x_get_termios_port(tty->driver_data,
-			&tty->termios.c_cflag, &baud);
-		tty_encode_baud_rate(tty, baud, baud);
-	} else {
-		tcflag_t cflag;
-		cflag = 0;
-		cp210x_get_termios_port(port, &cflag, &baud);
-	}
-}
-
-/*
- * cp210x_get_termios_port
- * This is the heart of cp210x_get_termios which always uses a &usb_serial_port.
- */
-static void cp210x_get_termios_port(struct usb_serial_port *port,
-	tcflag_t *cflagp, unsigned int *baudp)
-{
-	struct device *dev = &port->dev;
-	tcflag_t cflag;
-	struct cp210x_flow_ctl flow_ctl;
-	u32 baud;
-	u16 bits;
-	u32 ctl_hs;
-	u32 flow_repl;
-
-	cp210x_read_u32_reg(port, CP210X_GET_BAUDRATE, &baud);
-
-	dev_dbg(dev, "%s - baud rate = %d\n", __func__, baud);
-	*baudp = baud;
-
-	cflag = *cflagp;
-
-	cp210x_get_line_ctl(port, &bits);
-	cflag &= ~CSIZE;
-	switch (bits & BITS_DATA_MASK) {
-	case BITS_DATA_5:
-		dev_dbg(dev, "%s - data bits = 5\n", __func__);
-		cflag |= CS5;
-		break;
-	case BITS_DATA_6:
-		dev_dbg(dev, "%s - data bits = 6\n", __func__);
-		cflag |= CS6;
-		break;
-	case BITS_DATA_7:
-		dev_dbg(dev, "%s - data bits = 7\n", __func__);
-		cflag |= CS7;
-		break;
-	case BITS_DATA_8:
-		dev_dbg(dev, "%s - data bits = 8\n", __func__);
-		cflag |= CS8;
-		break;
-	case BITS_DATA_9:
-		dev_dbg(dev, "%s - data bits = 9 (not supported, using 8 data bits)\n", __func__);
-		cflag |= CS8;
-		bits &= ~BITS_DATA_MASK;
-		bits |= BITS_DATA_8;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown number of data bits, using 8\n", __func__);
-		cflag |= CS8;
-		bits &= ~BITS_DATA_MASK;
-		bits |= BITS_DATA_8;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	switch (bits & BITS_PARITY_MASK) {
-	case BITS_PARITY_NONE:
-		dev_dbg(dev, "%s - parity = NONE\n", __func__);
-		cflag &= ~PARENB;
-		break;
-	case BITS_PARITY_ODD:
-		dev_dbg(dev, "%s - parity = ODD\n", __func__);
-		cflag |= (PARENB|PARODD);
-		break;
-	case BITS_PARITY_EVEN:
-		dev_dbg(dev, "%s - parity = EVEN\n", __func__);
-		cflag &= ~PARODD;
-		cflag |= PARENB;
-		break;
-	case BITS_PARITY_MARK:
-		dev_dbg(dev, "%s - parity = MARK\n", __func__);
-		cflag |= (PARENB|PARODD|CMSPAR);
-		break;
-	case BITS_PARITY_SPACE:
-		dev_dbg(dev, "%s - parity = SPACE\n", __func__);
-		cflag &= ~PARODD;
-		cflag |= (PARENB|CMSPAR);
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown parity mode, disabling parity\n", __func__);
-		cflag &= ~PARENB;
-		bits &= ~BITS_PARITY_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	cflag &= ~CSTOPB;
-	switch (bits & BITS_STOP_MASK) {
-	case BITS_STOP_1:
-		dev_dbg(dev, "%s - stop bits = 1\n", __func__);
-		break;
-	case BITS_STOP_1_5:
-		dev_dbg(dev, "%s - stop bits = 1.5 (not supported, using 1 stop bit)\n", __func__);
-		bits &= ~BITS_STOP_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	case BITS_STOP_2:
-		dev_dbg(dev, "%s - stop bits = 2\n", __func__);
-		cflag |= CSTOPB;
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown number of stop bits, using 1 stop bit\n", __func__);
-		bits &= ~BITS_STOP_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
-			sizeof(flow_ctl));
-	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
-	if (ctl_hs & CP210X_SERIAL_CTS_HANDSHAKE) {
-		dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
-		/*
-		 * When the port is closed, the CP210x hardware disables
-		 * auto-RTS and RTS is deasserted but it leaves auto-CTS when
-		 * in hardware flow control mode. When re-opening the port, if
-		 * auto-CTS is enabled on the cp210x, then auto-RTS must be
-		 * re-enabled in the driver.
-		 */
-		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
-		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);
-		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
-		cp210x_write_reg_block(port,
-				CP210X_SET_FLOW,
-				&flow_ctl,
-				sizeof(flow_ctl));
-
-		cflag |= CRTSCTS;
-	} else {
-		dev_dbg(dev, "%s - flow control = NONE\n", __func__);
-		cflag &= ~CRTSCTS;
-	}
-
-	*cflagp = cflag;
-}
-
 struct cp210x_rate {
 	speed_t rate;
 	speed_t high;
@@ -1352,127 +1074,121 @@ static void cp210x_disable_event_mode(struct usb_serial_port *port)
 	port_priv->event_mode = false;
 }
 
+static bool cp210x_termios_change(const struct ktermios *a, const struct ktermios *b)
+{
+	bool iflag_change;
+
+	iflag_change = ((a->c_iflag ^ b->c_iflag) & INPCK);
+
+	return tty_termios_hw_change(a, b) || iflag_change;
+}
+
+static void cp210x_set_flow_control(struct tty_struct *tty,
+		struct usb_serial_port *port, struct ktermios *old_termios)
+{
+	struct cp210x_flow_ctl flow_ctl;
+	u32 flow_repl;
+	u32 ctl_hs;
+	int ret;
+
+	if (old_termios && C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS))
+		return;
+
+	ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
+			sizeof(flow_ctl));
+	if (ret)
+		return;
+
+	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
+	flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
+
+	ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
+	ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
+	ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
+	ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
+	ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
+
+	if (C_CRTSCTS(tty)) {
+		ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
+		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
+		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);
+	} else {
+		ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
+		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
+		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);
+	}
+
+	dev_dbg(&port->dev, "%s - ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
+			__func__, ctl_hs, flow_repl);
+
+	flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
+	flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
+
+	cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
+			sizeof(flow_ctl));
+}
+
 static void cp210x_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
-	struct device *dev = &port->dev;
-	unsigned int cflag, old_cflag;
+	struct cp210x_serial_private *priv = usb_get_serial_data(port->serial);
 	u16 bits;
+	int ret;
 
-	cflag = tty->termios.c_cflag;
-	old_cflag = old_termios->c_cflag;
+	if (old_termios && !cp210x_termios_change(&tty->termios, old_termios))
+		return;
 
-	if (tty->termios.c_ospeed != old_termios->c_ospeed)
+	if (!old_termios || tty->termios.c_ospeed != old_termios->c_ospeed)
 		cp210x_change_speed(tty, port, old_termios);
 
-	/* If the number of data bits is to be updated */
-	if ((cflag & CSIZE) != (old_cflag & CSIZE)) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_DATA_MASK;
-		switch (cflag & CSIZE) {
-		case CS5:
-			bits |= BITS_DATA_5;
-			dev_dbg(dev, "%s - data bits = 5\n", __func__);
-			break;
-		case CS6:
-			bits |= BITS_DATA_6;
-			dev_dbg(dev, "%s - data bits = 6\n", __func__);
-			break;
-		case CS7:
-			bits |= BITS_DATA_7;
-			dev_dbg(dev, "%s - data bits = 7\n", __func__);
-			break;
-		case CS8:
-		default:
-			bits |= BITS_DATA_8;
-			dev_dbg(dev, "%s - data bits = 8\n", __func__);
-			break;
-		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Number of data bits requested not supported by device\n");
+	/* CP2101 only supports CS8, 1 stop bit and non-stick parity. */
+	if (priv->partnum == CP210X_PARTNUM_CP2101) {
+		tty->termios.c_cflag &= ~(CSIZE | CSTOPB | CMSPAR);
+		tty->termios.c_cflag |= CS8;
 	}
 
-	if ((cflag     & (PARENB|PARODD|CMSPAR)) !=
-	    (old_cflag & (PARENB|PARODD|CMSPAR))) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_PARITY_MASK;
-		if (cflag & PARENB) {
-			if (cflag & CMSPAR) {
-				if (cflag & PARODD) {
-					bits |= BITS_PARITY_MARK;
-					dev_dbg(dev, "%s - parity = MARK\n", __func__);
-				} else {
-					bits |= BITS_PARITY_SPACE;
-					dev_dbg(dev, "%s - parity = SPACE\n", __func__);
-				}
-			} else {
-				if (cflag & PARODD) {
-					bits |= BITS_PARITY_ODD;
-					dev_dbg(dev, "%s - parity = ODD\n", __func__);
-				} else {
-					bits |= BITS_PARITY_EVEN;
-					dev_dbg(dev, "%s - parity = EVEN\n", __func__);
-				}
-			}
-		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Parity mode not supported by device\n");
+	bits = 0;
+
+	switch (C_CSIZE(tty)) {
+	case CS5:
+		bits |= BITS_DATA_5;
+		break;
+	case CS6:
+		bits |= BITS_DATA_6;
+		break;
+	case CS7:
+		bits |= BITS_DATA_7;
+		break;
+	case CS8:
+	default:
+		bits |= BITS_DATA_8;
+		break;
 	}
 
-	if ((cflag & CSTOPB) != (old_cflag & CSTOPB)) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_STOP_MASK;
-		if (cflag & CSTOPB) {
-			bits |= BITS_STOP_2;
-			dev_dbg(dev, "%s - stop bits = 2\n", __func__);
+	if (C_PARENB(tty)) {
+		if (C_CMSPAR(tty)) {
+			if (C_PARODD(tty))
+				bits |= BITS_PARITY_MARK;
+			else
+				bits |= BITS_PARITY_SPACE;
 		} else {
-			bits |= BITS_STOP_1;
-			dev_dbg(dev, "%s - stop bits = 1\n", __func__);
+			if (C_PARODD(tty))
+				bits |= BITS_PARITY_ODD;
+			else
+				bits |= BITS_PARITY_EVEN;
 		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Number of stop bits requested not supported by device\n");
 	}
 
-	if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
-		struct cp210x_flow_ctl flow_ctl;
-		u32 ctl_hs;
-		u32 flow_repl;
-
-		cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
-				sizeof(flow_ctl));
-		ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
-		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
-		dev_dbg(dev, "%s - read ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
-				__func__, ctl_hs, flow_repl);
-
-		ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
-		ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
-		ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
-		ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
-		ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
-		if (cflag & CRTSCTS) {
-			ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
-
-			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
-					CP210X_SERIAL_RTS_FLOW_CTL);
-			dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
-		} else {
-			ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
+	if (C_CSTOPB(tty))
+		bits |= BITS_STOP_2;
+	else
+		bits |= BITS_STOP_1;
 
-			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
-					CP210X_SERIAL_RTS_ACTIVE);
-			dev_dbg(dev, "%s - flow control = NONE\n", __func__);
-		}
+	ret = cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
+	if (ret)
+		dev_err(&port->dev, "failed to set line control: %d\n", ret);
 
-		dev_dbg(dev, "%s - write ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
-				__func__, ctl_hs, flow_repl);
-		flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
-		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
-		cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
-				sizeof(flow_ctl));
-	}
+	cp210x_set_flow_control(tty, port, old_termios);
 
 	/*
 	 * Enable event-insertion mode only if input parity checking is
@@ -1518,12 +1234,12 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
 	return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
 }
 
-static void cp210x_dtr_rts(struct usb_serial_port *p, int on)
+static void cp210x_dtr_rts(struct usb_serial_port *port, int on)
 {
 	if (on)
-		cp210x_tiocmset_port(p, TIOCM_DTR|TIOCM_RTS, 0);
+		cp210x_tiocmset_port(port, TIOCM_DTR | TIOCM_RTS, 0);
 	else
-		cp210x_tiocmset_port(p, 0, TIOCM_DTR|TIOCM_RTS);
+		cp210x_tiocmset_port(port, 0, TIOCM_DTR | TIOCM_RTS);
 }
 
 static int cp210x_tiocmget(struct tty_struct *tty)
@@ -1986,7 +1702,6 @@ static int cp210x_port_probe(struct usb_serial_port *port)
 {
 	struct usb_serial *serial = port->serial;
 	struct cp210x_port_private *port_priv;
-	int ret;
 
 	port_priv = kzalloc(sizeof(*port_priv), GFP_KERNEL);
 	if (!port_priv)
@@ -1996,12 +1711,6 @@ static int cp210x_port_probe(struct usb_serial_port *port)
 
 	usb_set_serial_port_data(port, port_priv);
 
-	ret = cp210x_detect_swapped_line_ctl(port);
-	if (ret) {
-		kfree(port_priv);
-		return ret;
-	}
-
 	return 0;
 }
 
diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 91055a191995..0ecd5316d85f 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -19,7 +19,6 @@
 #include <linux/tty_flip.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
-#include <linux/workqueue.h>
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 #include <linux/wait.h>
@@ -198,14 +197,13 @@ struct digi_port {
 	int dp_throttle_restart;
 	wait_queue_head_t dp_flush_wait;
 	wait_queue_head_t dp_close_wait;	/* wait queue for close */
-	struct work_struct dp_wakeup_work;
+	wait_queue_head_t write_wait;
 	struct usb_serial_port *dp_port;
 };
 
 
 /* Local Function Declarations */
 
-static void digi_wakeup_write_lock(struct work_struct *work);
 static int digi_write_oob_command(struct usb_serial_port *port,
 	unsigned char *buf, int count, int interruptible);
 static int digi_write_inb_command(struct usb_serial_port *port,
@@ -356,26 +354,6 @@ __releases(lock)
 	return timeout;
 }
 
-
-/*
- *  Digi Wakeup Write
- *
- *  Wake up port, line discipline, and tty processes sleeping
- *  on writes.
- */
-
-static void digi_wakeup_write_lock(struct work_struct *work)
-{
-	struct digi_port *priv =
-			container_of(work, struct digi_port, dp_wakeup_work);
-	struct usb_serial_port *port = priv->dp_port;
-	unsigned long flags;
-
-	spin_lock_irqsave(&priv->dp_port_lock, flags);
-	tty_port_tty_wakeup(&port->port);
-	spin_unlock_irqrestore(&priv->dp_port_lock, flags);
-}
-
 /*
  *  Digi Write OOB Command
  *
@@ -404,7 +382,7 @@ static int digi_write_oob_command(struct usb_serial_port *port,
 	while (count > 0) {
 		while (oob_priv->dp_write_urb_in_use) {
 			cond_wait_interruptible_timeout_irqrestore(
-				&oob_port->write_wait, DIGI_RETRY_TIMEOUT,
+				&oob_priv->write_wait, DIGI_RETRY_TIMEOUT,
 				&oob_priv->dp_port_lock, flags);
 			if (interruptible && signal_pending(current))
 				return -EINTR;
@@ -467,7 +445,7 @@ static int digi_write_inb_command(struct usb_serial_port *port,
 		while (priv->dp_write_urb_in_use &&
 		       time_before(jiffies, timeout)) {
 			cond_wait_interruptible_timeout_irqrestore(
-				&port->write_wait, DIGI_RETRY_TIMEOUT,
+				&priv->write_wait, DIGI_RETRY_TIMEOUT,
 				&priv->dp_port_lock, flags);
 			if (signal_pending(current))
 				return -EINTR;
@@ -546,7 +524,7 @@ static int digi_set_modem_signals(struct usb_serial_port *port,
 	while (oob_priv->dp_write_urb_in_use) {
 		spin_unlock(&port_priv->dp_port_lock);
 		cond_wait_interruptible_timeout_irqrestore(
-			&oob_port->write_wait, DIGI_RETRY_TIMEOUT,
+			&oob_priv->write_wait, DIGI_RETRY_TIMEOUT,
 			&oob_priv->dp_port_lock, flags);
 		if (interruptible && signal_pending(current))
 			return -EINTR;
@@ -911,9 +889,8 @@ static int digi_write(struct tty_struct *tty, struct usb_serial_port *port,
 	unsigned char *data = port->write_urb->transfer_buffer;
 	unsigned long flags = 0;
 
-	dev_dbg(&port->dev,
-		"digi_write: TOP: port=%d, count=%d, in_interrupt=%ld\n",
-		priv->dp_port_num, count, in_interrupt());
+	dev_dbg(&port->dev, "digi_write: TOP: port=%d, count=%d\n",
+		priv->dp_port_num, count);
 
 	/* copy user data (which can sleep) before getting spin lock */
 	count = min(count, port->bulk_out_size-2);
@@ -986,6 +963,7 @@ static void digi_write_bulk_callback(struct urb *urb)
 	unsigned long flags;
 	int ret = 0;
 	int status = urb->status;
+	bool wakeup;
 
 	/* port and serial sanity check */
 	if (port == NULL || (priv = usb_get_serial_port_data(port)) == NULL) {
@@ -1006,12 +984,13 @@ static void digi_write_bulk_callback(struct urb *urb)
 		dev_dbg(&port->dev, "digi_write_bulk_callback: oob callback\n");
 		spin_lock_irqsave(&priv->dp_port_lock, flags);
 		priv->dp_write_urb_in_use = 0;
-		wake_up_interruptible(&port->write_wait);
+		wake_up_interruptible(&priv->write_wait);
 		spin_unlock_irqrestore(&priv->dp_port_lock, flags);
 		return;
 	}
 
 	/* try to send any buffered data on this port */
+	wakeup = true;
 	spin_lock_irqsave(&priv->dp_port_lock, flags);
 	priv->dp_write_urb_in_use = 0;
 	if (priv->dp_out_buf_len > 0) {
@@ -1027,19 +1006,18 @@ static void digi_write_bulk_callback(struct urb *urb)
 		if (ret == 0) {
 			priv->dp_write_urb_in_use = 1;
 			priv->dp_out_buf_len = 0;
+			wakeup = false;
 		}
 	}
-	/* wake up processes sleeping on writes immediately */
-	tty_port_tty_wakeup(&port->port);
-	/* also queue up a wakeup at scheduler time, in case we */
-	/* lost the race in write_chan(). */
-	schedule_work(&priv->dp_wakeup_work);
-
 	spin_unlock_irqrestore(&priv->dp_port_lock, flags);
+
 	if (ret && ret != -EPERM)
 		dev_err_console(port,
 			"%s: usb_submit_urb failed, ret=%d, port=%d\n",
 			__func__, ret, priv->dp_port_num);
+
+	if (wakeup)
+		tty_port_tty_wakeup(&port->port);
 }
 
 static int digi_write_room(struct tty_struct *tty)
@@ -1239,11 +1217,9 @@ static int digi_port_init(struct usb_serial_port *port, unsigned port_num)
 	init_waitqueue_head(&priv->dp_transmit_idle_wait);
 	init_waitqueue_head(&priv->dp_flush_wait);
 	init_waitqueue_head(&priv->dp_close_wait);
-	INIT_WORK(&priv->dp_wakeup_work, digi_wakeup_write_lock);
+	init_waitqueue_head(&priv->write_wait);
 	priv->dp_port = port;
 
-	init_waitqueue_head(&port->write_wait);
-
 	usb_set_serial_port_data(port, priv);
 
 	return 0;
@@ -1508,13 +1484,14 @@ static int digi_read_oob_callback(struct urb *urb)
 			rts = C_CRTSCTS(tty);
 
 		if (tty && opcode == DIGI_CMD_READ_INPUT_SIGNALS) {
+			bool wakeup = false;
+
 			spin_lock_irqsave(&priv->dp_port_lock, flags);
 			/* convert from digi flags to termiox flags */
 			if (val & DIGI_READ_INPUT_SIGNALS_CTS) {
 				priv->dp_modem_signals |= TIOCM_CTS;
-				/* port must be open to use tty struct */
 				if (rts)
-					tty_port_tty_wakeup(&port->port);
+					wakeup = true;
 			} else {
 				priv->dp_modem_signals &= ~TIOCM_CTS;
 				/* port must be open to use tty struct */
@@ -1533,6 +1510,9 @@ static int digi_read_oob_callback(struct urb *urb)
 				priv->dp_modem_signals &= ~TIOCM_CD;
 
 			spin_unlock_irqrestore(&priv->dp_port_lock, flags);
+
+			if (wakeup)
+				tty_port_tty_wakeup(&port->port);
 		} else if (opcode == DIGI_CMD_TRANSMIT_IDLE) {
 			spin_lock_irqsave(&priv->dp_port_lock, flags);
 			priv->dp_transmit_idle = 1;
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index e0f4c3d9649c..94398f89e600 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1841,9 +1841,6 @@ static int ftdi_gpio_request(struct gpio_chip *gc, unsigned int offset)
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 	int result;
 
-	if (priv->gpio_altfunc & BIT(offset))
-		return -ENODEV;
-
 	mutex_lock(&priv->gpio_lock);
 	if (!priv->gpio_used) {
 		/* Set default pin states, as we cannot get them from device */
@@ -2002,6 +1999,25 @@ static int ftdi_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio,
 	return result;
 }
 
+static int ftdi_gpio_init_valid_mask(struct gpio_chip *gc,
+				     unsigned long *valid_mask,
+				     unsigned int ngpios)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	unsigned long map = priv->gpio_altfunc;
+
+	bitmap_complement(valid_mask, &map, ngpios);
+
+	if (bitmap_empty(valid_mask, ngpios))
+		dev_dbg(&port->dev, "no CBUS pin configured for GPIO\n");
+	else
+		dev_dbg(&port->dev, "CBUS%*pbl configured for GPIO\n", ngpios,
+			valid_mask);
+
+	return 0;
+}
+
 static int ftdi_read_eeprom(struct usb_serial *serial, void *dst, u16 addr,
 				u16 nbytes)
 {
@@ -2173,6 +2189,7 @@ static int ftdi_gpio_init(struct usb_serial_port *port)
 	priv->gc.get_direction = ftdi_gpio_direction_get;
 	priv->gc.direction_input = ftdi_gpio_direction_input;
 	priv->gc.direction_output = ftdi_gpio_direction_output;
+	priv->gc.init_valid_mask = ftdi_gpio_init_valid_mask;
 	priv->gc.get = ftdi_gpio_get;
 	priv->gc.set = ftdi_gpio_set;
 	priv->gc.get_multiple = ftdi_gpio_get_multiple;
diff --git a/drivers/usb/serial/iuu_phoenix.c b/drivers/usb/serial/iuu_phoenix.c
index b4ba79123d9d..f1201d4de297 100644
--- a/drivers/usb/serial/iuu_phoenix.c
+++ b/drivers/usb/serial/iuu_phoenix.c
@@ -850,7 +850,6 @@ static int iuu_uart_baud(struct usb_serial_port *port, u32 baud_base,
 	default:
 		kfree(dataout);
 		return IUU_INVALID_PARAMETER;
-		break;
 	}
 
 	switch (parity & 0xF0) {
@@ -864,7 +863,6 @@ static int iuu_uart_baud(struct usb_serial_port *port, u32 baud_base,
 	default:
 		kfree(dataout);
 		return IUU_INVALID_PARAMETER;
-		break;
 	}
 
 	status = bulk_immediate(port, dataout, DataCount);
diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index c1333919716b..e6f933e8d25f 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -5,12 +5,12 @@
  * Copyright (C) 1999 - 2001 Greg Kroah-Hartman	<greg@kroah.com>
  * Copyright (C) 1999, 2000 Brian Warner	<warner@lothar.com>
  * Copyright (C) 2000 Al Borchers		<borchers@steinerpoint.com>
+ * Copyright (C) 2020 Johan Hovold <johan@kernel.org>
  *
  * See Documentation/usb/usb-serial.rst for more information on using this
  * driver
  */
 
-
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
@@ -25,30 +25,19 @@
 #include <linux/usb/serial.h>
 #include <linux/usb/ezusb.h>
 
-/* make a simple define to handle if we are compiling keyspan_pda or xircom support */
-#if IS_ENABLED(CONFIG_USB_SERIAL_KEYSPAN_PDA)
-	#define KEYSPAN
-#else
-	#undef KEYSPAN
-#endif
-#if IS_ENABLED(CONFIG_USB_SERIAL_XIRCOM)
-	#define XIRCOM
-#else
-	#undef XIRCOM
-#endif
-
-#define DRIVER_AUTHOR "Brian Warner <warner@lothar.com>"
+#define DRIVER_AUTHOR "Brian Warner <warner@lothar.com>, Johan Hovold <johan@kernel.org>"
 #define DRIVER_DESC "USB Keyspan PDA Converter driver"
 
+#define KEYSPAN_TX_THRESHOLD	128
+
 struct keyspan_pda_private {
 	int			tx_room;
-	int			tx_throttled;
-	struct work_struct			wakeup_work;
-	struct work_struct			unthrottle_work;
+	struct work_struct	unthrottle_work;
 	struct usb_serial	*serial;
 	struct usb_serial_port	*port;
 };
 
+static int keyspan_pda_write_start(struct usb_serial_port *port);
 
 #define KEYSPAN_VENDOR_ID		0x06cd
 #define KEYSPAN_PDA_FAKE_ID		0x0103
@@ -62,18 +51,13 @@ struct keyspan_pda_private {
 #define ENTREGA_FAKE_ID			0x8093
 
 static const struct usb_device_id id_table_combined[] = {
-#ifdef KEYSPAN
 	{ USB_DEVICE(KEYSPAN_VENDOR_ID, KEYSPAN_PDA_FAKE_ID) },
-#endif
-#ifdef XIRCOM
 	{ USB_DEVICE(XIRCOM_VENDOR_ID, XIRCOM_FAKE_ID) },
 	{ USB_DEVICE(XIRCOM_VENDOR_ID, XIRCOM_FAKE_ID_2) },
 	{ USB_DEVICE(ENTREGA_VENDOR_ID, ENTREGA_FAKE_ID) },
-#endif
 	{ USB_DEVICE(KEYSPAN_VENDOR_ID, KEYSPAN_PDA_ID) },
 	{ }						/* Terminating entry */
 };
-
 MODULE_DEVICE_TABLE(usb, id_table_combined);
 
 static const struct usb_device_id id_table_std[] = {
@@ -81,46 +65,71 @@ static const struct usb_device_id id_table_std[] = {
 	{ }						/* Terminating entry */
 };
 
-#ifdef KEYSPAN
 static const struct usb_device_id id_table_fake[] = {
 	{ USB_DEVICE(KEYSPAN_VENDOR_ID, KEYSPAN_PDA_FAKE_ID) },
-	{ }						/* Terminating entry */
-};
-#endif
-
-#ifdef XIRCOM
-static const struct usb_device_id id_table_fake_xircom[] = {
 	{ USB_DEVICE(XIRCOM_VENDOR_ID, XIRCOM_FAKE_ID) },
 	{ USB_DEVICE(XIRCOM_VENDOR_ID, XIRCOM_FAKE_ID_2) },
 	{ USB_DEVICE(ENTREGA_VENDOR_ID, ENTREGA_FAKE_ID) },
-	{ }
+	{ }						/* Terminating entry */
 };
-#endif
 
-static void keyspan_pda_wakeup_write(struct work_struct *work)
+static int keyspan_pda_get_write_room(struct keyspan_pda_private *priv)
 {
-	struct keyspan_pda_private *priv =
-		container_of(work, struct keyspan_pda_private, wakeup_work);
 	struct usb_serial_port *port = priv->port;
+	struct usb_serial *serial = port->serial;
+	u8 *room;
+	int rc;
+
+	room = kmalloc(1, GFP_KERNEL);
+	if (!room)
+		return -ENOMEM;
 
-	tty_port_tty_wakeup(&port->port);
+	rc = usb_control_msg(serial->dev,
+			     usb_rcvctrlpipe(serial->dev, 0),
+			     6, /* write_room */
+			     USB_TYPE_VENDOR | USB_RECIP_INTERFACE
+			     | USB_DIR_IN,
+			     0, /* value: 0 means "remaining room" */
+			     0, /* index */
+			     room,
+			     1,
+			     2000);
+	if (rc != 1) {
+		if (rc >= 0)
+			rc = -EIO;
+		dev_dbg(&port->dev, "roomquery failed: %d\n", rc);
+		goto out_free;
+	}
+
+	dev_dbg(&port->dev, "roomquery says %d\n", *room);
+	rc = *room;
+out_free:
+	kfree(room);
+
+	return rc;
 }
 
 static void keyspan_pda_request_unthrottle(struct work_struct *work)
 {
 	struct keyspan_pda_private *priv =
 		container_of(work, struct keyspan_pda_private, unthrottle_work);
-	struct usb_serial *serial = priv->serial;
+	struct usb_serial_port *port = priv->port;
+	struct usb_serial *serial = port->serial;
+	unsigned long flags;
 	int result;
 
-	/* ask the device to tell us when the tx buffer becomes
-	   sufficiently empty */
+	dev_dbg(&port->dev, "%s\n", __func__);
+
+	/*
+	 * Ask the device to tell us when the tx buffer becomes
+	 * sufficiently empty.
+	 */
 	result = usb_control_msg(serial->dev,
 				 usb_sndctrlpipe(serial->dev, 0),
 				 7, /* request_unthrottle */
 				 USB_TYPE_VENDOR | USB_RECIP_INTERFACE
 				 | USB_DIR_OUT,
-				 16, /* value: threshold */
+				 KEYSPAN_TX_THRESHOLD,
 				 0, /* index */
 				 NULL,
 				 0,
@@ -128,9 +137,20 @@ static void keyspan_pda_request_unthrottle(struct work_struct *work)
 	if (result < 0)
 		dev_dbg(&serial->dev->dev, "%s - error %d from usb_control_msg\n",
 			__func__, result);
+	/*
+	 * Need to check available space after requesting notification in case
+	 * buffer is already empty so that no notification is sent.
+	 */
+	result = keyspan_pda_get_write_room(priv);
+	if (result > KEYSPAN_TX_THRESHOLD) {
+		spin_lock_irqsave(&port->lock, flags);
+		priv->tx_room = max(priv->tx_room, result);
+		spin_unlock_irqrestore(&port->lock, flags);
+
+		usb_serial_port_softint(port);
+	}
 }
 
-
 static void keyspan_pda_rx_interrupt(struct urb *urb)
 {
 	struct usb_serial_port *port = urb->context;
@@ -139,6 +159,8 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
 	int retval;
 	int status = urb->status;
 	struct keyspan_pda_private *priv;
+	unsigned long flags;
+
 	priv = usb_get_serial_port_data(port);
 
 	switch (status) {
@@ -172,18 +194,22 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
 		break;
 	case 1:
 		/* status interrupt */
-		if (len < 3) {
+		if (len < 2) {
 			dev_warn(&port->dev, "short interrupt message received\n");
 			break;
 		}
-		dev_dbg(&port->dev, "rx int, d1=%d, d2=%d\n", data[1], data[2]);
+		dev_dbg(&port->dev, "rx int, d1=%d\n", data[1]);
 		switch (data[1]) {
 		case 1: /* modemline change */
 			break;
 		case 2: /* tx unthrottle interrupt */
-			priv->tx_throttled = 0;
-			/* queue up a wakeup at scheduler time */
-			schedule_work(&priv->wakeup_work);
+			spin_lock_irqsave(&port->lock, flags);
+			priv->tx_room = max(priv->tx_room, KEYSPAN_TX_THRESHOLD);
+			spin_unlock_irqrestore(&port->lock, flags);
+
+			keyspan_pda_write_start(port);
+
+			usb_serial_port_softint(port);
 			break;
 		default:
 			break;
@@ -201,31 +227,30 @@ exit:
 			__func__, retval);
 }
 
-
 static void keyspan_pda_rx_throttle(struct tty_struct *tty)
 {
-	/* stop receiving characters. We just turn off the URB request, and
-	   let chars pile up in the device. If we're doing hardware
-	   flowcontrol, the device will signal the other end when its buffer
-	   fills up. If we're doing XON/XOFF, this would be a good time to
-	   send an XOFF, although it might make sense to foist that off
-	   upon the device too. */
 	struct usb_serial_port *port = tty->driver_data;
 
+	/*
+	 * Stop receiving characters. We just turn off the URB request, and
+	 * let chars pile up in the device. If we're doing hardware
+	 * flowcontrol, the device will signal the other end when its buffer
+	 * fills up. If we're doing XON/XOFF, this would be a good time to
+	 * send an XOFF, although it might make sense to foist that off upon
+	 * the device too.
+	 */
 	usb_kill_urb(port->interrupt_in_urb);
 }
 
-
 static void keyspan_pda_rx_unthrottle(struct tty_struct *tty)
 {
 	struct usb_serial_port *port = tty->driver_data;
-	/* just restart the receive interrupt URB */
 
+	/* just restart the receive interrupt URB */
 	if (usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL))
 		dev_dbg(&port->dev, "usb_submit_urb(read urb) failed\n");
 }
 
-
 static speed_t keyspan_pda_setbaud(struct usb_serial *serial, speed_t baud)
 {
 	int rc;
@@ -267,8 +292,6 @@ static speed_t keyspan_pda_setbaud(struct usb_serial *serial, speed_t baud)
 		baud = 9600;
 	}
 
-	/* rather than figure out how to sleep while waiting for this
-	   to complete, I just use the "legacy" API. */
 	rc = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
 			     0, /* set baud */
 			     USB_TYPE_VENDOR
@@ -281,10 +304,10 @@ static speed_t keyspan_pda_setbaud(struct usb_serial *serial, speed_t baud)
 			     2000); /* timeout */
 	if (rc < 0)
 		return 0;
+
 	return baud;
 }
 
-
 static void keyspan_pda_break_ctl(struct tty_struct *tty, int break_state)
 {
 	struct usb_serial_port *port = tty->driver_data;
@@ -296,6 +319,7 @@ static void keyspan_pda_break_ctl(struct tty_struct *tty, int break_state)
 		value = 1; /* start break */
 	else
 		value = 0; /* clear break */
+
 	result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
 			4, /* set break */
 			USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_OUT,
@@ -303,39 +327,35 @@ static void keyspan_pda_break_ctl(struct tty_struct *tty, int break_state)
 	if (result < 0)
 		dev_dbg(&port->dev, "%s - error %d from usb_control_msg\n",
 			__func__, result);
-	/* there is something funky about this.. the TCSBRK that 'cu' performs
-	   ought to translate into a break_ctl(-1),break_ctl(0) pair HZ/4
-	   seconds apart, but it feels like the break sent isn't as long as it
-	   is on /dev/ttyS0 */
 }
 
-
 static void keyspan_pda_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
 	struct usb_serial *serial = port->serial;
 	speed_t speed;
 
-	/* cflag specifies lots of stuff: number of stop bits, parity, number
-	   of data bits, baud. What can the device actually handle?:
-	   CSTOPB (1 stop bit or 2)
-	   PARENB (parity)
-	   CSIZE (5bit .. 8bit)
-	   There is minimal hw support for parity (a PSW bit seems to hold the
-	   parity of whatever is in the accumulator). The UART either deals
-	   with 10 bits (start, 8 data, stop) or 11 bits (start, 8 data,
-	   1 special, stop). So, with firmware changes, we could do:
-	   8N1: 10 bit
-	   8N2: 11 bit, extra bit always (mark?)
-	   8[EOMS]1: 11 bit, extra bit is parity
-	   7[EOMS]1: 10 bit, b0/b7 is parity
-	   7[EOMS]2: 11 bit, b0/b7 is parity, extra bit always (mark?)
-
-	   HW flow control is dictated by the tty->termios.c_cflags & CRTSCTS
-	   bit.
-
-	   For now, just do baud. */
-
+	/*
+	 * cflag specifies lots of stuff: number of stop bits, parity, number
+	 * of data bits, baud. What can the device actually handle?:
+	 * CSTOPB (1 stop bit or 2)
+	 * PARENB (parity)
+	 * CSIZE (5bit .. 8bit)
+	 * There is minimal hw support for parity (a PSW bit seems to hold the
+	 * parity of whatever is in the accumulator). The UART either deals
+	 * with 10 bits (start, 8 data, stop) or 11 bits (start, 8 data,
+	 * 1 special, stop). So, with firmware changes, we could do:
+	 * 8N1: 10 bit
+	 * 8N2: 11 bit, extra bit always (mark?)
+	 * 8[EOMS]1: 11 bit, extra bit is parity
+	 * 7[EOMS]1: 10 bit, b0/b7 is parity
+	 * 7[EOMS]2: 11 bit, b0/b7 is parity, extra bit always (mark?)
+	 *
+	 * HW flow control is dictated by the tty->termios.c_cflags & CRTSCTS
+	 * bit.
+	 *
+	 * For now, just do baud.
+	 */
 	speed = tty_get_baud_rate(tty);
 	speed = keyspan_pda_setbaud(serial, speed);
 
@@ -344,17 +364,19 @@ static void keyspan_pda_set_termios(struct tty_struct *tty,
 		/* It hasn't changed so.. */
 		speed = tty_termios_baud_rate(old_termios);
 	}
-	/* Only speed can change so copy the old h/w parameters
-	   then encode the new speed */
+	/*
+	 * Only speed can change so copy the old h/w parameters then encode
+	 * the new speed.
+	 */
 	tty_termios_copy_hw(&tty->termios, old_termios);
 	tty_encode_baud_rate(tty, speed, speed);
 }
 
-
-/* modem control pins: DTR and RTS are outputs and can be controlled.
-   DCD, RI, DSR, CTS are inputs and can be read. All outputs can also be
-   read. The byte passed is: DTR(b7) DCD RI DSR CTS RTS(b2) unused unused */
-
+/*
+ * Modem control pins: DTR and RTS are outputs and can be controlled.
+ * DCD, RI, DSR, CTS are inputs and can be read. All outputs can also be
+ * read. The byte passed is: DTR(b7) DCD RI DSR CTS RTS(b2) unused unused.
+ */
 static int keyspan_pda_get_modem_info(struct usb_serial *serial,
 				      unsigned char *value)
 {
@@ -378,7 +400,6 @@ static int keyspan_pda_get_modem_info(struct usb_serial *serial,
 	return rc;
 }
 
-
 static int keyspan_pda_set_modem_info(struct usb_serial *serial,
 				      unsigned char value)
 {
@@ -401,13 +422,14 @@ static int keyspan_pda_tiocmget(struct tty_struct *tty)
 	rc = keyspan_pda_get_modem_info(serial, &status);
 	if (rc < 0)
 		return rc;
-	value =
-		((status & (1<<7)) ? TIOCM_DTR : 0) |
-		((status & (1<<6)) ? TIOCM_CAR : 0) |
-		((status & (1<<5)) ? TIOCM_RNG : 0) |
-		((status & (1<<4)) ? TIOCM_DSR : 0) |
-		((status & (1<<3)) ? TIOCM_CTS : 0) |
-		((status & (1<<2)) ? TIOCM_RTS : 0);
+
+	value = ((status & BIT(7)) ? TIOCM_DTR : 0) |
+		((status & BIT(6)) ? TIOCM_CAR : 0) |
+		((status & BIT(5)) ? TIOCM_RNG : 0) |
+		((status & BIT(4)) ? TIOCM_DSR : 0) |
+		((status & BIT(3)) ? TIOCM_CTS : 0) |
+		((status & BIT(2)) ? TIOCM_RTS : 0);
+
 	return value;
 }
 
@@ -424,186 +446,127 @@ static int keyspan_pda_tiocmset(struct tty_struct *tty,
 		return rc;
 
 	if (set & TIOCM_RTS)
-		status |= (1<<2);
+		status |= BIT(2);
 	if (set & TIOCM_DTR)
-		status |= (1<<7);
+		status |= BIT(7);
 
 	if (clear & TIOCM_RTS)
-		status &= ~(1<<2);
+		status &= ~BIT(2);
 	if (clear & TIOCM_DTR)
-		status &= ~(1<<7);
+		status &= ~BIT(7);
 	rc = keyspan_pda_set_modem_info(serial, status);
 	return rc;
 }
 
-static int keyspan_pda_write(struct tty_struct *tty,
-	struct usb_serial_port *port, const unsigned char *buf, int count)
+static int keyspan_pda_write_start(struct usb_serial_port *port)
 {
-	struct usb_serial *serial = port->serial;
-	int request_unthrottle = 0;
-	int rc = 0;
-	struct keyspan_pda_private *priv;
+	struct keyspan_pda_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	struct urb *urb;
+	int count;
+	int room;
+	int rc;
 
-	priv = usb_get_serial_port_data(port);
-	/* guess how much room is left in the device's ring buffer, and if we
-	   want to send more than that, check first, updating our notion of
-	   what is left. If our write will result in no room left, ask the
-	   device to give us an interrupt when the room available rises above
-	   a threshold, and hold off all writers (eventually, those using
-	   select() or poll() too) until we receive that unthrottle interrupt.
-	   Block if we can't write anything at all, otherwise write as much as
-	   we can. */
-	if (count == 0) {
-		dev_dbg(&port->dev, "write request of 0 bytes\n");
-		return 0;
-	}
+	/*
+	 * Guess how much room is left in the device's ring buffer. If our
+	 * write will result in no room left, ask the device to give us an
+	 * interrupt when the room available rises above a threshold but also
+	 * query how much room is currently available (in case our guess was
+	 * too conservative and the buffer is already empty when the
+	 * unthrottle work is scheduled).
+	 */
+
+	/*
+	 * We might block because of:
+	 * the TX urb is in-flight (wait until it completes)
+	 * the device is full (wait until it says there is room)
+	 */
+	spin_lock_irqsave(&port->lock, flags);
+
+	room = priv->tx_room;
+	count = kfifo_len(&port->write_fifo);
 
-	/* we might block because of:
-	   the TX urb is in-flight (wait until it completes)
-	   the device is full (wait until it says there is room)
-	*/
-	spin_lock_bh(&port->lock);
-	if (!test_bit(0, &port->write_urbs_free) || priv->tx_throttled) {
-		spin_unlock_bh(&port->lock);
+	if (!test_bit(0, &port->write_urbs_free) || count == 0 || room == 0) {
+		spin_unlock_irqrestore(&port->lock, flags);
 		return 0;
 	}
-	clear_bit(0, &port->write_urbs_free);
-	spin_unlock_bh(&port->lock);
-
-	/* At this point the URB is in our control, nobody else can submit it
-	   again (the only sudden transition was the one from EINPROGRESS to
-	   finished).  Also, the tx process is not throttled. So we are
-	   ready to write. */
-
-	count = (count > port->bulk_out_size) ? port->bulk_out_size : count;
-
-	/* Check if we might overrun the Tx buffer.   If so, ask the
-	   device how much room it really has.  This is done only on
-	   scheduler time, since usb_control_msg() sleeps. */
-	if (count > priv->tx_room && !in_interrupt()) {
-		u8 *room;
-
-		room = kmalloc(1, GFP_KERNEL);
-		if (!room) {
-			rc = -ENOMEM;
-			goto exit;
-		}
+	__clear_bit(0, &port->write_urbs_free);
 
-		rc = usb_control_msg(serial->dev,
-				     usb_rcvctrlpipe(serial->dev, 0),
-				     6, /* write_room */
-				     USB_TYPE_VENDOR | USB_RECIP_INTERFACE
-				     | USB_DIR_IN,
-				     0, /* value: 0 means "remaining room" */
-				     0, /* index */
-				     room,
-				     1,
-				     2000);
-		if (rc > 0) {
-			dev_dbg(&port->dev, "roomquery says %d\n", *room);
-			priv->tx_room = *room;
-		}
-		kfree(room);
-		if (rc < 0) {
-			dev_dbg(&port->dev, "roomquery failed\n");
-			goto exit;
-		}
-		if (rc == 0) {
-			dev_dbg(&port->dev, "roomquery returned 0 bytes\n");
-			rc = -EIO; /* device didn't return any data */
-			goto exit;
-		}
-	}
-	if (count > priv->tx_room) {
-		/* we're about to completely fill the Tx buffer, so
-		   we'll be throttled afterwards. */
-		count = priv->tx_room;
-		request_unthrottle = 1;
-	}
+	if (count > room)
+		count = room;
+	if (count > port->bulk_out_size)
+		count = port->bulk_out_size;
 
-	if (count) {
-		/* now transfer data */
-		memcpy(port->write_urb->transfer_buffer, buf, count);
-		/* send the data out the bulk port */
-		port->write_urb->transfer_buffer_length = count;
+	urb = port->write_urb;
+	count = kfifo_out(&port->write_fifo, urb->transfer_buffer, count);
+	urb->transfer_buffer_length = count;
 
-		priv->tx_room -= count;
+	port->tx_bytes += count;
+	priv->tx_room -= count;
 
-		rc = usb_submit_urb(port->write_urb, GFP_ATOMIC);
-		if (rc) {
-			dev_dbg(&port->dev, "usb_submit_urb(write bulk) failed\n");
-			goto exit;
-		}
-	} else {
-		/* There wasn't any room left, so we are throttled until
-		   the buffer empties a bit */
-		request_unthrottle = 1;
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	dev_dbg(&port->dev, "%s - count = %d, txroom = %d\n", __func__, count, room);
+
+	rc = usb_submit_urb(urb, GFP_ATOMIC);
+	if (rc) {
+		dev_dbg(&port->dev, "usb_submit_urb(write bulk) failed\n");
+
+		spin_lock_irqsave(&port->lock, flags);
+		port->tx_bytes -= count;
+		priv->tx_room = max(priv->tx_room, room + count);
+		__set_bit(0, &port->write_urbs_free);
+		spin_unlock_irqrestore(&port->lock, flags);
+
+		return rc;
 	}
 
-	if (request_unthrottle) {
-		priv->tx_throttled = 1; /* block writers */
+	if (count == room)
 		schedule_work(&priv->unthrottle_work);
-	}
 
-	rc = count;
-exit:
-	if (rc < 0)
-		set_bit(0, &port->write_urbs_free);
-	return rc;
+	return count;
 }
 
-
 static void keyspan_pda_write_bulk_callback(struct urb *urb)
 {
 	struct usb_serial_port *port = urb->context;
-	struct keyspan_pda_private *priv;
+	unsigned long flags;
 
-	set_bit(0, &port->write_urbs_free);
-	priv = usb_get_serial_port_data(port);
+	spin_lock_irqsave(&port->lock, flags);
+	port->tx_bytes -= urb->transfer_buffer_length;
+	__set_bit(0, &port->write_urbs_free);
+	spin_unlock_irqrestore(&port->lock, flags);
 
-	/* queue up a wakeup at scheduler time */
-	schedule_work(&priv->wakeup_work);
-}
+	keyspan_pda_write_start(port);
 
+	usb_serial_port_softint(port);
+}
 
-static int keyspan_pda_write_room(struct tty_struct *tty)
+static int keyspan_pda_write(struct tty_struct *tty, struct usb_serial_port *port,
+		const unsigned char *buf, int count)
 {
-	struct usb_serial_port *port = tty->driver_data;
-	struct keyspan_pda_private *priv;
-	priv = usb_get_serial_port_data(port);
-	/* used by n_tty.c for processing of tabs and such. Giving it our
-	   conservative guess is probably good enough, but needs testing by
-	   running a console through the device. */
-	return priv->tx_room;
-}
+	int rc;
 
+	dev_dbg(&port->dev, "%s - count = %d\n", __func__, count);
 
-static int keyspan_pda_chars_in_buffer(struct tty_struct *tty)
-{
-	struct usb_serial_port *port = tty->driver_data;
-	struct keyspan_pda_private *priv;
-	unsigned long flags;
-	int ret = 0;
+	if (!count)
+		return 0;
 
-	priv = usb_get_serial_port_data(port);
+	count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
 
-	/* when throttled, return at least WAKEUP_CHARS to tell select() (via
-	   n_tty.c:normal_poll() ) that we're not writeable. */
+	rc = keyspan_pda_write_start(port);
+	if (rc)
+		return rc;
 
-	spin_lock_irqsave(&port->lock, flags);
-	if (!test_bit(0, &port->write_urbs_free) || priv->tx_throttled)
-		ret = 256;
-	spin_unlock_irqrestore(&port->lock, flags);
-	return ret;
+	return count;
 }
 
-
 static void keyspan_pda_dtr_rts(struct usb_serial_port *port, int on)
 {
 	struct usb_serial *serial = port->serial;
 
 	if (on)
-		keyspan_pda_set_modem_info(serial, (1 << 7) | (1 << 2));
+		keyspan_pda_set_modem_info(serial, BIT(7) | BIT(2));
 	else
 		keyspan_pda_set_modem_info(serial, 0);
 }
@@ -612,74 +575,63 @@ static void keyspan_pda_dtr_rts(struct usb_serial_port *port, int on)
 static int keyspan_pda_open(struct tty_struct *tty,
 					struct usb_serial_port *port)
 {
-	struct usb_serial *serial = port->serial;
-	u8 *room;
-	int rc = 0;
-	struct keyspan_pda_private *priv;
+	struct keyspan_pda_private *priv = usb_get_serial_port_data(port);
+	int rc;
 
 	/* find out how much room is in the Tx ring */
-	room = kmalloc(1, GFP_KERNEL);
-	if (!room)
-		return -ENOMEM;
+	rc = keyspan_pda_get_write_room(priv);
+	if (rc < 0)
+		return rc;
 
-	rc = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
-			     6, /* write_room */
-			     USB_TYPE_VENDOR | USB_RECIP_INTERFACE
-			     | USB_DIR_IN,
-			     0, /* value */
-			     0, /* index */
-			     room,
-			     1,
-			     2000);
-	if (rc < 0) {
-		dev_dbg(&port->dev, "%s - roomquery failed\n", __func__);
-		goto error;
-	}
-	if (rc == 0) {
-		dev_dbg(&port->dev, "%s - roomquery returned 0 bytes\n", __func__);
-		rc = -EIO;
-		goto error;
-	}
-	priv = usb_get_serial_port_data(port);
-	priv->tx_room = *room;
-	priv->tx_throttled = *room ? 0 : 1;
+	spin_lock_irq(&port->lock);
+	priv->tx_room = rc;
+	spin_unlock_irq(&port->lock);
 
-	/*Start reading from the device*/
 	rc = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 	if (rc) {
 		dev_dbg(&port->dev, "%s - usb_submit_urb(read int) failed\n", __func__);
-		goto error;
+		return rc;
 	}
-error:
-	kfree(room);
-	return rc;
+
+	return 0;
 }
+
 static void keyspan_pda_close(struct usb_serial_port *port)
 {
-	usb_kill_urb(port->write_urb);
+	struct keyspan_pda_private *priv = usb_get_serial_port_data(port);
+
+	/*
+	 * Stop the interrupt URB first as its completion handler may submit
+	 * the write URB.
+	 */
 	usb_kill_urb(port->interrupt_in_urb);
-}
+	usb_kill_urb(port->write_urb);
+
+	cancel_work_sync(&priv->unthrottle_work);
 
+	spin_lock_irq(&port->lock);
+	kfifo_reset(&port->write_fifo);
+	spin_unlock_irq(&port->lock);
+}
 
 /* download the firmware to a "fake" device (pre-renumeration) */
 static int keyspan_pda_fake_startup(struct usb_serial *serial)
 {
+	unsigned int vid = le16_to_cpu(serial->dev->descriptor.idVendor);
 	const char *fw_name;
 
 	/* download the firmware here ... */
 	ezusb_fx1_set_reset(serial->dev, 1);
 
-	if (0) { ; }
-#ifdef KEYSPAN
-	else if (le16_to_cpu(serial->dev->descriptor.idVendor) == KEYSPAN_VENDOR_ID)
+	switch (vid) {
+	case KEYSPAN_VENDOR_ID:
 		fw_name = "keyspan_pda/keyspan_pda.fw";
-#endif
-#ifdef XIRCOM
-	else if ((le16_to_cpu(serial->dev->descriptor.idVendor) == XIRCOM_VENDOR_ID) ||
-		 (le16_to_cpu(serial->dev->descriptor.idVendor) == ENTREGA_VENDOR_ID))
+		break;
+	case XIRCOM_VENDOR_ID:
+	case ENTREGA_VENDOR_ID:
 		fw_name = "keyspan_pda/xircom_pgs.fw";
-#endif
-	else {
+		break;
+	default:
 		dev_err(&serial->dev->dev, "%s: unknown vendor, aborting.\n",
 			__func__);
 		return -ENODEV;
@@ -691,19 +643,17 @@ static int keyspan_pda_fake_startup(struct usb_serial *serial)
 		return -ENOENT;
 	}
 
-	/* after downloading firmware Renumeration will occur in a
-	  moment and the new device will bind to the real driver */
+	/*
+	 * After downloading firmware renumeration will occur in a moment and
+	 * the new device will bind to the real driver.
+	 */
 
-	/* we want this device to fail to have a driver assigned to it. */
+	/* We want this device to fail to have a driver assigned to it. */
 	return 1;
 }
 
-#ifdef KEYSPAN
 MODULE_FIRMWARE("keyspan_pda/keyspan_pda.fw");
-#endif
-#ifdef XIRCOM
 MODULE_FIRMWARE("keyspan_pda/xircom_pgs.fw");
-#endif
 
 static int keyspan_pda_port_probe(struct usb_serial_port *port)
 {
@@ -714,9 +664,7 @@ static int keyspan_pda_port_probe(struct usb_serial_port *port)
 	if (!priv)
 		return -ENOMEM;
 
-	INIT_WORK(&priv->wakeup_work, keyspan_pda_wakeup_write);
 	INIT_WORK(&priv->unthrottle_work, keyspan_pda_request_unthrottle);
-	priv->serial = port->serial;
 	priv->port = port;
 
 	usb_set_serial_port_data(port, priv);
@@ -734,7 +682,6 @@ static int keyspan_pda_port_remove(struct usb_serial_port *port)
 	return 0;
 }
 
-#ifdef KEYSPAN
 static struct usb_serial_driver keyspan_pda_fake_device = {
 	.driver = {
 		.owner =	THIS_MODULE,
@@ -745,20 +692,6 @@ static struct usb_serial_driver keyspan_pda_fake_device = {
 	.num_ports =		1,
 	.attach =		keyspan_pda_fake_startup,
 };
-#endif
-
-#ifdef XIRCOM
-static struct usb_serial_driver xircom_pgs_fake_device = {
-	.driver = {
-		.owner =	THIS_MODULE,
-		.name =		"xircom_no_firm",
-	},
-	.description =		"Xircom / Entrega PGS - (prerenumeration)",
-	.id_table =		id_table_fake_xircom,
-	.num_ports =		1,
-	.attach =		keyspan_pda_fake_startup,
-};
-#endif
 
 static struct usb_serial_driver keyspan_pda_device = {
 	.driver = {
@@ -774,10 +707,8 @@ static struct usb_serial_driver keyspan_pda_device = {
 	.open =			keyspan_pda_open,
 	.close =		keyspan_pda_close,
 	.write =		keyspan_pda_write,
-	.write_room =		keyspan_pda_write_room,
-	.write_bulk_callback = 	keyspan_pda_write_bulk_callback,
+	.write_bulk_callback =	keyspan_pda_write_bulk_callback,
 	.read_int_callback =	keyspan_pda_rx_interrupt,
-	.chars_in_buffer =	keyspan_pda_chars_in_buffer,
 	.throttle =		keyspan_pda_rx_throttle,
 	.unthrottle =		keyspan_pda_rx_unthrottle,
 	.set_termios =		keyspan_pda_set_termios,
@@ -790,12 +721,7 @@ static struct usb_serial_driver keyspan_pda_device = {
 
 static struct usb_serial_driver * const serial_drivers[] = {
 	&keyspan_pda_device,
-#ifdef KEYSPAN
 	&keyspan_pda_fake_device,
-#endif
-#ifdef XIRCOM
-	&xircom_pgs_fake_device,
-#endif
 	NULL
 };
 
diff --git a/drivers/usb/serial/mos7720.c b/drivers/usb/serial/mos7720.c
index 5eed1078fac8..41ee2984a0df 100644
--- a/drivers/usb/serial/mos7720.c
+++ b/drivers/usb/serial/mos7720.c
@@ -79,14 +79,6 @@ MODULE_DEVICE_TABLE(usb, id_table);
 #define DCR_INIT_VAL       0x0c	/* SLCTIN, nINIT */
 #define ECR_INIT_VAL       0x00	/* SPP mode */
 
-struct urbtracker {
-	struct mos7715_parport  *mos_parport;
-	struct list_head        urblist_entry;
-	struct kref             ref_count;
-	struct urb              *urb;
-	struct usb_ctrlrequest	*setup;
-};
-
 enum mos7715_pp_modes {
 	SPP = 0<<5,
 	PS2 = 1<<5,      /* moschip calls this 'NIBBLE' mode */
@@ -96,12 +88,9 @@ enum mos7715_pp_modes {
 struct mos7715_parport {
 	struct parport          *pp;	       /* back to containing struct */
 	struct kref             ref_count;     /* to instance of this struct */
-	struct list_head        deferred_urbs; /* list deferred async urbs */
-	struct list_head        active_urbs;   /* list async urbs in flight */
-	spinlock_t              listlock;      /* protects list access */
 	bool                    msg_pending;   /* usb sync call pending */
 	struct completion       syncmsg_compl; /* usb sync call completed */
-	struct tasklet_struct   urb_tasklet;   /* for sending deferred urbs */
+	struct work_struct      work;          /* restore deferred writes */
 	struct usb_serial       *serial;       /* back to containing struct */
 	__u8	                shadowECR;     /* parallel port regs... */
 	__u8	                shadowDCR;
@@ -265,174 +254,8 @@ static void destroy_mos_parport(struct kref *kref)
 	kfree(mos_parport);
 }
 
-static void destroy_urbtracker(struct kref *kref)
-{
-	struct urbtracker *urbtrack =
-		container_of(kref, struct urbtracker, ref_count);
-	struct mos7715_parport *mos_parport = urbtrack->mos_parport;
-
-	usb_free_urb(urbtrack->urb);
-	kfree(urbtrack->setup);
-	kfree(urbtrack);
-	kref_put(&mos_parport->ref_count, destroy_mos_parport);
-}
-
 /*
- * This runs as a tasklet when sending an urb in a non-blocking parallel
- * port callback had to be deferred because the disconnect mutex could not be
- * obtained at the time.
- */
-static void send_deferred_urbs(struct tasklet_struct *t)
-{
-	int ret_val;
-	unsigned long flags;
-	struct mos7715_parport *mos_parport = from_tasklet(mos_parport, t,
-							   urb_tasklet);
-	struct urbtracker *urbtrack, *tmp;
-	struct list_head *cursor, *next;
-	struct device *dev;
-
-	/* if release function ran, game over */
-	if (unlikely(mos_parport->serial == NULL))
-		return;
-
-	dev = &mos_parport->serial->dev->dev;
-
-	/* try again to get the mutex */
-	if (!mutex_trylock(&mos_parport->serial->disc_mutex)) {
-		dev_dbg(dev, "%s: rescheduling tasklet\n", __func__);
-		tasklet_schedule(&mos_parport->urb_tasklet);
-		return;
-	}
-
-	/* if device disconnected, game over */
-	if (unlikely(mos_parport->serial->disconnected)) {
-		mutex_unlock(&mos_parport->serial->disc_mutex);
-		return;
-	}
-
-	spin_lock_irqsave(&mos_parport->listlock, flags);
-	if (list_empty(&mos_parport->deferred_urbs)) {
-		spin_unlock_irqrestore(&mos_parport->listlock, flags);
-		mutex_unlock(&mos_parport->serial->disc_mutex);
-		dev_dbg(dev, "%s: deferred_urbs list empty\n", __func__);
-		return;
-	}
-
-	/* move contents of deferred_urbs list to active_urbs list and submit */
-	list_for_each_safe(cursor, next, &mos_parport->deferred_urbs)
-		list_move_tail(cursor, &mos_parport->active_urbs);
-	list_for_each_entry_safe(urbtrack, tmp, &mos_parport->active_urbs,
-			    urblist_entry) {
-		ret_val = usb_submit_urb(urbtrack->urb, GFP_ATOMIC);
-		dev_dbg(dev, "%s: urb submitted\n", __func__);
-		if (ret_val) {
-			dev_err(dev, "usb_submit_urb() failed: %d\n", ret_val);
-			list_del(&urbtrack->urblist_entry);
-			kref_put(&urbtrack->ref_count, destroy_urbtracker);
-		}
-	}
-	spin_unlock_irqrestore(&mos_parport->listlock, flags);
-	mutex_unlock(&mos_parport->serial->disc_mutex);
-}
-
-/* callback for parallel port control urbs submitted asynchronously */
-static void async_complete(struct urb *urb)
-{
-	struct urbtracker *urbtrack = urb->context;
-	int status = urb->status;
-	unsigned long flags;
-
-	if (unlikely(status))
-		dev_dbg(&urb->dev->dev, "%s - nonzero urb status received: %d\n", __func__, status);
-
-	/* remove the urbtracker from the active_urbs list */
-	spin_lock_irqsave(&urbtrack->mos_parport->listlock, flags);
-	list_del(&urbtrack->urblist_entry);
-	spin_unlock_irqrestore(&urbtrack->mos_parport->listlock, flags);
-	kref_put(&urbtrack->ref_count, destroy_urbtracker);
-}
-
-static int write_parport_reg_nonblock(struct mos7715_parport *mos_parport,
-				      enum mos_regs reg, __u8 data)
-{
-	struct urbtracker *urbtrack;
-	int ret_val;
-	unsigned long flags;
-	struct usb_serial *serial = mos_parport->serial;
-	struct usb_device *usbdev = serial->dev;
-
-	/* create and initialize the control urb and containing urbtracker */
-	urbtrack = kmalloc(sizeof(struct urbtracker), GFP_ATOMIC);
-	if (!urbtrack)
-		return -ENOMEM;
-
-	urbtrack->urb = usb_alloc_urb(0, GFP_ATOMIC);
-	if (!urbtrack->urb) {
-		kfree(urbtrack);
-		return -ENOMEM;
-	}
-	urbtrack->setup = kmalloc(sizeof(*urbtrack->setup), GFP_ATOMIC);
-	if (!urbtrack->setup) {
-		usb_free_urb(urbtrack->urb);
-		kfree(urbtrack);
-		return -ENOMEM;
-	}
-	urbtrack->setup->bRequestType = (__u8)0x40;
-	urbtrack->setup->bRequest = (__u8)0x0e;
-	urbtrack->setup->wValue = cpu_to_le16(get_reg_value(reg, dummy));
-	urbtrack->setup->wIndex = cpu_to_le16(get_reg_index(reg));
-	urbtrack->setup->wLength = 0;
-	usb_fill_control_urb(urbtrack->urb, usbdev,
-			     usb_sndctrlpipe(usbdev, 0),
-			     (unsigned char *)urbtrack->setup,
-			     NULL, 0, async_complete, urbtrack);
-	kref_get(&mos_parport->ref_count);
-	urbtrack->mos_parport = mos_parport;
-	kref_init(&urbtrack->ref_count);
-	INIT_LIST_HEAD(&urbtrack->urblist_entry);
-
-	/*
-	 * get the disconnect mutex, or add tracker to the deferred_urbs list
-	 * and schedule a tasklet to try again later
-	 */
-	if (!mutex_trylock(&serial->disc_mutex)) {
-		spin_lock_irqsave(&mos_parport->listlock, flags);
-		list_add_tail(&urbtrack->urblist_entry,
-			      &mos_parport->deferred_urbs);
-		spin_unlock_irqrestore(&mos_parport->listlock, flags);
-		tasklet_schedule(&mos_parport->urb_tasklet);
-		dev_dbg(&usbdev->dev, "tasklet scheduled\n");
-		return 0;
-	}
-
-	/* bail if device disconnected */
-	if (serial->disconnected) {
-		kref_put(&urbtrack->ref_count, destroy_urbtracker);
-		mutex_unlock(&serial->disc_mutex);
-		return -ENODEV;
-	}
-
-	/* add the tracker to the active_urbs list and submit */
-	spin_lock_irqsave(&mos_parport->listlock, flags);
-	list_add_tail(&urbtrack->urblist_entry, &mos_parport->active_urbs);
-	spin_unlock_irqrestore(&mos_parport->listlock, flags);
-	ret_val = usb_submit_urb(urbtrack->urb, GFP_ATOMIC);
-	mutex_unlock(&serial->disc_mutex);
-	if (ret_val) {
-		dev_err(&usbdev->dev,
-			"%s: submit_urb() failed: %d\n", __func__, ret_val);
-		spin_lock_irqsave(&mos_parport->listlock, flags);
-		list_del(&urbtrack->urblist_entry);
-		spin_unlock_irqrestore(&mos_parport->listlock, flags);
-		kref_put(&urbtrack->ref_count, destroy_urbtracker);
-		return ret_val;
-	}
-	return 0;
-}
-
-/*
- * This is the the common top part of all parallel port callback operations that
+ * This is the common top part of all parallel port callback operations that
  * send synchronous messages to the device.  This implements convoluted locking
  * that avoids two scenarios: (1) a port operation is called after usbserial
  * has called our release function, at which point struct mos7715_parport has
@@ -458,6 +281,10 @@ static int parport_prologue(struct parport *pp)
 	reinit_completion(&mos_parport->syncmsg_compl);
 	spin_unlock(&release_lock);
 
+	/* ensure writes from restore are submitted before new requests */
+	if (work_pending(&mos_parport->work))
+		flush_work(&mos_parport->work);
+
 	mutex_lock(&mos_parport->serial->disc_mutex);
 	if (mos_parport->serial->disconnected) {
 		/* device disconnected */
@@ -482,6 +309,26 @@ static inline void parport_epilogue(struct parport *pp)
 	complete(&mos_parport->syncmsg_compl);
 }
 
+static void deferred_restore_writes(struct work_struct *work)
+{
+	struct mos7715_parport *mos_parport;
+
+	mos_parport = container_of(work, struct mos7715_parport, work);
+
+	mutex_lock(&mos_parport->serial->disc_mutex);
+
+	/* if device disconnected, game over */
+	if (mos_parport->serial->disconnected)
+		goto done;
+
+	write_mos_reg(mos_parport->serial, dummy, MOS7720_DCR,
+		      mos_parport->shadowDCR);
+	write_mos_reg(mos_parport->serial, dummy, MOS7720_ECR,
+		      mos_parport->shadowECR);
+done:
+	mutex_unlock(&mos_parport->serial->disc_mutex);
+}
+
 static void parport_mos7715_write_data(struct parport *pp, unsigned char d)
 {
 	struct mos7715_parport *mos_parport = pp->private_data;
@@ -639,10 +486,10 @@ static void parport_mos7715_restore_state(struct parport *pp,
 		spin_unlock(&release_lock);
 		return;
 	}
-	write_parport_reg_nonblock(mos_parport, MOS7720_DCR,
-				   mos_parport->shadowDCR);
-	write_parport_reg_nonblock(mos_parport, MOS7720_ECR,
-				   mos_parport->shadowECR);
+	mos_parport->shadowDCR = s->u.pc.ctr;
+	mos_parport->shadowECR = s->u.pc.ecr;
+
+	schedule_work(&mos_parport->work);
 	spin_unlock(&release_lock);
 }
 
@@ -712,12 +559,9 @@ static int mos7715_parport_init(struct usb_serial *serial)
 
 	mos_parport->msg_pending = false;
 	kref_init(&mos_parport->ref_count);
-	spin_lock_init(&mos_parport->listlock);
-	INIT_LIST_HEAD(&mos_parport->active_urbs);
-	INIT_LIST_HEAD(&mos_parport->deferred_urbs);
 	usb_set_serial_data(serial, mos_parport); /* hijack private pointer */
 	mos_parport->serial = serial;
-	tasklet_setup(&mos_parport->urb_tasklet, send_deferred_urbs);
+	INIT_WORK(&mos_parport->work, deferred_restore_writes);
 	init_completion(&mos_parport->syncmsg_compl);
 
 	/* cycle parallel port reset bit */
@@ -1867,8 +1711,6 @@ static void mos7720_release(struct usb_serial *serial)
 
 	if (le16_to_cpu(serial->dev->descriptor.idProduct)
 	    == MOSCHIP_DEVICE_ID_7715) {
-		struct urbtracker *urbtrack;
-		unsigned long flags;
 		struct mos7715_parport *mos_parport =
 			usb_get_serial_data(serial);
 
@@ -1881,21 +1723,17 @@ static void mos7720_release(struct usb_serial *serial)
 		if (mos_parport->msg_pending)
 			wait_for_completion_timeout(&mos_parport->syncmsg_compl,
 					    msecs_to_jiffies(MOS_WDR_TIMEOUT));
+		/*
+		 * If delayed work is currently scheduled, wait for it to
+		 * complete. This also implies barriers that ensure the
+		 * below serial clearing is not hoisted above the ->work.
+		 */
+		cancel_work_sync(&mos_parport->work);
 
 		parport_remove_port(mos_parport->pp);
 		usb_set_serial_data(serial, NULL);
 		mos_parport->serial = NULL;
 
-		/* if tasklet currently scheduled, wait for it to complete */
-		tasklet_kill(&mos_parport->urb_tasklet);
-
-		/* unlink any urbs sent by the tasklet  */
-		spin_lock_irqsave(&mos_parport->listlock, flags);
-		list_for_each_entry(urbtrack,
-				    &mos_parport->active_urbs,
-				    urblist_entry)
-			usb_unlink_urb(urbtrack->urb);
-		spin_unlock_irqrestore(&mos_parport->listlock, flags);
 		parport_del_port(mos_parport->pp);
 
 		kref_put(&mos_parport->ref_count, destroy_mos_parport);
diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 56d6f6d83bd7..2c21e34235bb 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -563,6 +563,9 @@ static void option_instat_callback(struct urb *urb);
 
 /* Device flags */
 
+/* Highest interface number which can be used with NCTRL() and RSVD() */
+#define FLAG_IFNUM_MAX	7
+
 /* Interface does not support modem-control requests */
 #define NCTRL(ifnum)	((BIT(ifnum) & 0xff) << 8)
 
@@ -2101,6 +2104,14 @@ static struct usb_serial_driver * const serial_drivers[] = {
 
 module_usb_serial_driver(serial_drivers, option_ids);
 
+static bool iface_is_reserved(unsigned long device_flags, u8 ifnum)
+{
+	if (ifnum > FLAG_IFNUM_MAX)
+		return false;
+
+	return device_flags & RSVD(ifnum);
+}
+
 static int option_probe(struct usb_serial *serial,
 			const struct usb_device_id *id)
 {
@@ -2117,7 +2128,7 @@ static int option_probe(struct usb_serial *serial,
 	 * the same class/subclass/protocol as the serial interfaces.  Look at
 	 * the Windows driver .INF files for reserved interface numbers.
 	 */
-	if (device_flags & RSVD(iface_desc->bInterfaceNumber))
+	if (iface_is_reserved(device_flags, iface_desc->bInterfaceNumber))
 		return -ENODEV;
 
 	/*
@@ -2133,6 +2144,14 @@ static int option_probe(struct usb_serial *serial,
 	return 0;
 }
 
+static bool iface_no_modem_control(unsigned long device_flags, u8 ifnum)
+{
+	if (ifnum > FLAG_IFNUM_MAX)
+		return false;
+
+	return device_flags & NCTRL(ifnum);
+}
+
 static int option_attach(struct usb_serial *serial)
 {
 	struct usb_interface_descriptor *iface_desc;
@@ -2148,7 +2167,7 @@ static int option_attach(struct usb_serial *serial)
 
 	iface_desc = &serial->interface->cur_altsetting->desc;
 
-	if (!(device_flags & NCTRL(iface_desc->bInterfaceNumber)))
+	if (!iface_no_modem_control(device_flags, iface_desc->bInterfaceNumber))
 		data->use_send_setup = 1;
 
 	if (device_flags & ZLP)
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index 8e67eff9039f..1c09b922f8b0 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -62,7 +62,6 @@
  * @bulk_out_endpointAddress: endpoint address for the bulk out pipe for this
  *	port.
  * @flags: usb serial port flags
- * @write_wait: a wait_queue_head_t used by the port.
  * @work: work queue entry for the line discipline waking up.
  * @dev: pointer to the serial device
  *
@@ -108,7 +107,6 @@ struct usb_serial_port {
 	int			tx_bytes;
 
 	unsigned long		flags;
-	wait_queue_head_t	write_wait;
 	struct work_struct	work;
 	unsigned long		sysrq; /* sysrq timeout */
 	struct device		dev;