Date:	Wed, 10 Dec 2014 14:04:12 +0100
From:	Johan Hovold <johan@...nel.org>
To:	George McCollister <george.mccollister@...il.com>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, johan@...nel.org
Subject: Re: [PATCH] USB: serial: add nt124 usb to serial driver

On Mon, Dec 08, 2014 at 05:24:17PM -0600, George McCollister wrote:
> This driver is for the NovaTech 124 4x serial expansion board for the
> NovaTech OrionLXm.
> 
> Firmware source code can be found here:
> https://github.com/novatechweb/nt124

Great, and thanks for the patch!

> Signed-off-by: George McCollister <george.mccollister@...il.com>
> ---
>  drivers/usb/serial/Kconfig  |   9 +
>  drivers/usb/serial/Makefile |   1 +
>  drivers/usb/serial/nt124.c  | 429 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 439 insertions(+)
>  create mode 100644 drivers/usb/serial/nt124.c
> 
> diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
> index a69f7cd..6dfc340 100644
> --- a/drivers/usb/serial/Kconfig
> +++ b/drivers/usb/serial/Kconfig
> @@ -509,6 +509,15 @@ config USB_SERIAL_NAVMAN
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called navman.
>  
> +config USB_SERIAL_NT124
> +	tristate "USB nt124 serial device"

USB NovaTech 124 Serial Driver (or NovaTech nt124)

> +	help
> +	  Say Y here if you want to use the NovaTech 124 4x USB to serial
> +	  board.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called nt124.
> +
>  config USB_SERIAL_PL2303
>  	tristate "USB Prolific 2303 Single Port Serial Driver"
>  	help
> diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
> index 349d9df..f88eaab 100644
> --- a/drivers/usb/serial/Makefile
> +++ b/drivers/usb/serial/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_USB_SERIAL_MOS7720)		+= mos7720.o
>  obj-$(CONFIG_USB_SERIAL_MOS7840)		+= mos7840.o
>  obj-$(CONFIG_USB_SERIAL_MXUPORT)		+= mxuport.o
>  obj-$(CONFIG_USB_SERIAL_NAVMAN)			+= navman.o
> +obj-$(CONFIG_USB_SERIAL_NT124)			+= nt124.o
>  obj-$(CONFIG_USB_SERIAL_OMNINET)		+= omninet.o
>  obj-$(CONFIG_USB_SERIAL_OPTICON)		+= opticon.o
>  obj-$(CONFIG_USB_SERIAL_OPTION)			+= option.o
> diff --git a/drivers/usb/serial/nt124.c b/drivers/usb/serial/nt124.c
> new file mode 100644
> index 0000000..d7557ff
> --- /dev/null
> +++ b/drivers/usb/serial/nt124.c
> @@ -0,0 +1,429 @@
> +/*
> + * nt124.c

Put a brief description here instead.

> + *
> + * Copyright (c) 2014 NovaTech LLC
> + *
> + * Driver for nt124 4x serial board based on STM32F103

For example use something like this above.

> + *
> + * Portions derived from the cdc-acm driver
> + *
> + * The original intention was to implement a cdc-acm compliant
> + * 4x USB to serial converter in the STM32F103 however several problems arose.
> + *   The STM32F103 didn't have enough end points to implement 4 ports.
> + *   CTS control was required by the application.
> + *   Accurate notification of transmission completion was required.
> + *   RTSCTS flow control support was required.
> + *
> + * The interrupt endpoint was eliminated and the control line information
> + * was moved to the first two bytes of the in endpoint message. CTS control

bulk in endpoint

> + * and mechanisms to enable RTSCTS flow control and deliver TXEMPTY
> + * information were added.
> + *
> + * Firmware source code can be found here:
> + * https://github.com/novatechweb/nt124
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/tty.h>
> +#include <linux/tty_driver.h>
> +#include <linux/tty_flip.h>
> +#include <linux/module.h>
> +#include <linux/usb.h>
> +#include <linux/usb/serial.h>
> +#include <asm/unaligned.h>
> +
> +#define NT124_VID		0x2aeb
> +#define NT124_USB_PID		124
> +
> +#define DRIVER_AUTHOR "George McCollister <george.mccollister@...il.com>"
> +#define DRIVER_DESC "nt124 USB serial driver"

Just use the MODULE macros directly (at the end of the file), no need
for the defines.

> +
> +static const struct usb_device_id id_table[] = {
> +	{ USB_DEVICE(NT124_VID, NT124_USB_PID) },
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(usb, id_table);
> +
> +/*
> + * Output control lines.
> + */
> +

No new line.

> +#define NT124_CTRL_DTR		0x01
> +#define NT124_CTRL_RTS		0x02
> +
> +/*
> + * Input control lines and line errors.
> + */
> +

Same here.

> +#define NT124_CTRL_DCD		0x01
> +#define NT124_CTRL_DSR		0x02
> +#define NT124_CTRL_BRK		0x04
> +#define NT124_CTRL_RI		0x08
> +#define NT124_CTRL_FRAMING	0x10
> +#define NT124_CTRL_PARITY	0x20
> +#define NT124_CTRL_OVERRUN	0x40
> +#define NT124_CTRL_TXEMPTY	0x80
> +#define NT124_CTRL_CTS		0x100
> +
> +#define USB_NT124_REQ_SET_LINE_CODING		0x20
> +#define USB_NT124_REQ_SET_CONTROL_LINE_STATE	0x22
> +#define USB_NT124_REQ_SEND_BREAK		0x23
> +#define USB_NT124_SET_FLOW_CONTROL		0x90
> +
> +struct nt124_line_coding {
> +	__le32	dwDTERate;
> +	u8	bCharFormat;
> +	u8	bParityType;
> +	u8	bDataBits;
> +} __packed;

__packed not needed.

> +
> +struct nt124_private {
> +	/* USB interface */

Superfluous comment.

> +	u16 bInterfaceNumber;
> +	/* input control lines (DCD, DSR, RI, break, overruns) */
> +	unsigned int ctrlin;
> +	/* output control lines (DTR, RTS) */
> +	unsigned int ctrlout;

Locking is missing for both of these (cdc-acm isn't always a great
example).

Use u16 for both?

> +	/* termios CLOCAL */
> +	unsigned char clocal;

Not needed (see below).

> +	/* bits, stop, parity */

Superfluous comment.

> +	struct nt124_line_coding line;
> +	int serial_transmit;

Comment on this one, or just call it tx_empty.

And use bool.

> +	unsigned int flowctrl;

Don't think you need this one either (more below).

> +};


> +
> +static int nt124_ctrl_msg(struct usb_serial_port *port, int request, int value,
> +			  void *buf, int len)

Use u16 (or unsigned int) for request and value, size_t for len.

> +{
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	int retval;
> +
> +	retval = usb_control_msg(port->serial->dev,
> +			usb_sndctrlpipe(port->serial->dev, 0),
> +			request, USB_TYPE_CLASS | USB_RECIP_INTERFACE, value,
> +			priv->bInterfaceNumber,
> +			buf, len, 5000);

Use a define for the timeout (e.g. USB_CTRL_SET_TIMEOUT).

> +
> +	dev_dbg(&port->dev,
> +			"%s - rq 0x%02x, val %#x, len %#x, result %d\n",

Request and val are 16-bit so use %04x for both, and %zu for len.

> +			__func__, request, value, len, retval);
> +
> +	return retval < 0 ? retval : 0;

Avoid ?: constructs.

Add proper error handling and add a dev_err for that case.

> +}
> +
> +#define nt124_set_control(port, control) \
> +	nt124_ctrl_msg(port, USB_NT124_REQ_SET_CONTROL_LINE_STATE, control, \
> +	NULL, 0)
> +#define nt124_set_line(port, line) \
> +	nt124_ctrl_msg(port, USB_NT124_REQ_SET_LINE_CODING, 0, line, \
> +	sizeof *(line))
> +#define nt124_send_break(port, ms) \
> +	nt124_ctrl_msg(port, USB_NT124_REQ_SEND_BREAK, ms, NULL, 0)
> +#define nt124_set_flowctrl(port, flowctrl) \
> +	nt124_ctrl_msg(port, USB_NT124_SET_FLOW_CONTROL, flowctrl, NULL, 0)

Don't use macros for these. Either call the ctrl_msg helper directly or
define proper inline functions.

> +
> +static void nt124_process_notify(struct usb_serial_port *port,

Rename process_status?

> +				 struct nt124_private *priv,
> +				 unsigned char *data)
> +{
> +	int newctrl;

Use an unsigned type.

> +	unsigned long flags;
> +
> +	newctrl = get_unaligned_le16(data);
> +	if (newctrl & NT124_CTRL_TXEMPTY) {
> +		spin_lock_irqsave(&port->lock, flags);
> +		priv->serial_transmit = 0;
> +		spin_unlock_irqrestore(&port->lock, flags);
> +		tty_port_tty_wakeup(&port->port);
> +	}

Just store tx_empty. No need to do the wake up and not sure you'll need
the locking (see below).

> +
> +	if (!priv->clocal && (priv->ctrlin & ~newctrl & NT124_CTRL_DCD)) {
> +		dev_dbg(&port->dev, "%s - calling hangup\n",
> +				__func__);
> +		tty_port_tty_hangup(&port->port, false);
> +	}

Call usb_serial_handle_dcd_change() unconditionally when DCD has changed
here instead.

> +
> +	priv->ctrlin = newctrl;

Locking missing.

> +}
> +
> +static void nt124_process_read_urb(struct urb *urb)
> +{
> +	struct usb_serial_port *port = urb->context;
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	unsigned char *data = (unsigned char *)urb->transfer_buffer;
> +
> +	if (urb->actual_length < 2)
> +		return;
> +
> +	nt124_process_notify(port, priv, data);
> +
> +	if (urb->actual_length == 2)
> +		return;
> +
> +	tty_insert_flip_string(&port->port, &data[2],
> +			urb->actual_length - 2);

No need to break line.

Use a temporary for length as well.

> +	tty_flip_buffer_push(&port->port);
> +}
> +
> +static int nt124_tiocmget(struct tty_struct *tty)
> +{
> +	struct usb_serial_port *port = tty->driver_data;
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +
> +	return (priv->ctrlout & NT124_CTRL_DTR ? TIOCM_DTR : 0) |
> +	       (priv->ctrlout & NT124_CTRL_RTS ? TIOCM_RTS : 0) |
> +	       (priv->ctrlin  & NT124_CTRL_DSR ? TIOCM_DSR : 0) |
> +	       (priv->ctrlin  & NT124_CTRL_RI  ? TIOCM_RI  : 0) |
> +	       (priv->ctrlin  & NT124_CTRL_DCD ? TIOCM_CD  : 0) |
> +	       (priv->ctrlin  & NT124_CTRL_CTS ? TIOCM_CTS : 0);

Locking is missing. Use temporary variables.

> +}
> +
> +static int nt124_port_tiocmset(struct usb_serial_port *port,
> +			       unsigned int set, unsigned int clear)
> +{
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	unsigned int newctrl;
> +
> +	newctrl = priv->ctrlout;

Locking throughout.

> +	set = (set & TIOCM_DTR ? NT124_CTRL_DTR : 0) |
> +		(set & TIOCM_RTS ? NT124_CTRL_RTS : 0);
> +	clear = (clear & TIOCM_DTR ? NT124_CTRL_DTR : 0) |
> +		(clear & TIOCM_RTS ? NT124_CTRL_RTS : 0);

Expand these without the ?:.

> +
> +	newctrl = (newctrl & ~clear) | set;
> +
> +	if (priv->ctrlout == newctrl)
> +		return 0;

Add newline.

> +	return nt124_set_control(port, priv->ctrlout = newctrl);

Don't do assignments in the argument list.

Also use usb_translate_errors on any error returned from USB core before
passing it to user space here.

> +}
> +
> +static int nt124_tiocmset(struct tty_struct *tty,
> +			  unsigned int set, unsigned int clear)
> +{
> +	struct usb_serial_port *port = tty->driver_data;
> +
> +	return nt124_port_tiocmset(port, set, clear);
> +}
> +
> +static void nt124_dtr_rts(struct usb_serial_port *port, int on)
> +{
> +	if (on)
> +		nt124_port_tiocmset(port, TIOCM_DTR|TIOCM_RTS, 0);

Spaces around |.

> +	else
> +		nt124_port_tiocmset(port, 0, TIOCM_DTR|TIOCM_RTS);

Ditto.

> +}
> +
> +static void nt124_set_termios(struct tty_struct *tty,
> +			      struct usb_serial_port *port,
> +			      struct ktermios *termios_old)
> +{
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	struct ktermios *termios = &tty->termios;
> +	struct nt124_line_coding newline;
> +	int newctrl = priv->ctrlout;
> +
> +	newline.dwDTERate = cpu_to_le32(tty_get_baud_rate(tty));
> +	newline.bCharFormat = termios->c_cflag & CSTOPB ? 2 : 0;

Do you support 1.5 stop bits (e.g. when using 5 data bits)?

> +	newline.bParityType = termios->c_cflag & PARENB ?
> +				(termios->c_cflag & PARODD ? 1 : 2) +
> +				(termios->c_cflag & CMSPAR ? 2 : 0) : 0;

This hardly readable. Don't use ?:

Add new line.

> +	switch (termios->c_cflag & CSIZE) {

C_CSIZE(tty)

> +	case CS5:
> +		newline.bDataBits = 5;
> +		break;
> +	case CS6:
> +		newline.bDataBits = 6;
> +		break;
> +	case CS7:
> +		newline.bDataBits = 7;
> +		break;
> +	case CS8:
> +	default:
> +		newline.bDataBits = 8;
> +		break;
> +	}
> +	priv->clocal = ((termios->c_cflag & CLOCAL) != 0);

Not needed.

> +
> +	if (C_BAUD(tty) == B0) {
> +		newline.dwDTERate = priv->line.dwDTERate;
> +		newctrl &= ~NT124_CTRL_DTR;
> +	} else if (termios_old && (termios_old->c_cflag & CBAUD) == B0) {
> +		newctrl |=  NT124_CTRL_DTR;
> +	}

You need to raise or lower RTS here as well.

And you might need to take flow control into account as well (e.g. see
mxuport driver).

> +
> +	if (newctrl != priv->ctrlout)
> +		nt124_set_control(port, priv->ctrlout = newctrl);

No assignments in argument lists.

Locking.

> +
> +	if (memcmp(&priv->line, &newline, sizeof(newline))) {
> +		memcpy(&priv->line, &newline, sizeof(newline));
> +		dev_dbg(&port->dev, "%s - set line: %d %d %d %d\n",
> +			__func__,

%u

> +			le32_to_cpu(newline.dwDTERate),
> +			newline.bCharFormat, newline.bParityType,
> +			newline.bDataBits);
> +		nt124_set_line(port, &priv->line);
> +	}
> +
> +	if (termios->c_cflag & CRTSCTS && !priv->flowctrl) {

C_CRTSCTS(tty), just compare with old termios for changes, no need to
store flowctrl.

> +		priv->flowctrl = 1;
> +		nt124_set_flowctrl(port, priv->flowctrl);
> +	} else if (!(termios->c_cflag & CRTSCTS) && priv->flowctrl) {
> +		priv->flowctrl = 0;
> +		nt124_set_flowctrl(port, priv->flowctrl);
> +	}
> +}
> +
> +static void nt124_write_bulk_callback(struct urb *urb)
> +{
> +	unsigned long flags;
> +	struct usb_serial_port *port = urb->context;
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i) {
> +		if (port->write_urbs[i] == urb)
> +			break;
> +	}
> +	spin_lock_irqsave(&port->lock, flags);
> +	port->tx_bytes -= urb->transfer_buffer_length;
> +	if (!urb->status)
> +		priv->serial_transmit = 1;

Why do you do this?

This functions is just a copy of usb_serial_generic_write_bulk_callback
apart from this, and you probably don't need it.

> +	set_bit(i, &port->write_urbs_free);
> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	switch (urb->status) {
> +	case 0:
> +		break;
> +	case -ENOENT:
> +	case -ECONNRESET:
> +	case -ESHUTDOWN:
> +		dev_dbg(&port->dev, "%s - urb stopped: %d\n",
> +							__func__, urb->status);
> +		return;
> +	case -EPIPE:
> +		dev_err_console(port, "%s - urb stopped: %d\n",
> +							__func__, urb->status);
> +		return;
> +	default:
> +		dev_err_console(port, "%s - nonzero urb status: %d\n",
> +							__func__, urb->status);
> +		goto resubmit;
> +	}
> +
> +resubmit:
> +	usb_serial_generic_write_start(port, GFP_ATOMIC);
> +	usb_serial_port_softint(port);
> +}
> +
> +static int nt124_chars_in_buffer(struct tty_struct *tty)
> +{
> +	struct usb_serial_port *port = tty->driver_data;
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	unsigned long flags;
> +	int chars;
> +
> +	if (!port->bulk_out_size)
> +		return 0;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	chars = kfifo_len(&port->write_fifo) + port->tx_bytes +
> +		priv->serial_transmit;

This is not correct.

Implement the tx_empty() callback instead, and use the generic
chars_in_buffer implementation.

> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
> +	return chars;
> +}
> +
> +static void nt124_break_ctl(struct tty_struct *tty, int state)
> +{
> +	struct usb_serial_port *port = tty->driver_data;
> +	int retval;
> +
> +	retval = nt124_send_break(port, state ? 0xffff : 0);

No ?:

Use defines for 0xffff and 0 (e.g. break on and off).

> +	if (retval < 0)
> +		dev_dbg(&port->dev, "%s - send break failed\n", __func__);

dev_err

> +}
> +
> +static int nt124_open(struct tty_struct *tty,
> +		      struct usb_serial_port *port)
> +{
> +	struct nt124_private *priv = usb_get_serial_port_data(port);
> +	int result = 0;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	port->throttled = 0;
> +	port->throttle_req = 0;
> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	priv->flowctrl = 0;

Drop this and keep the current settings.

> +	nt124_set_termios(tty, port, NULL);
> +	nt124_set_flowctrl(port, priv->flowctrl);

Drop this. This is handled by tty and dtr_rts().

> +
> +	if (port->bulk_in_size)
> +		result = usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);

Call usb_serial_generic_open() instead (and skip the throttle-flags bit
above).

> +
> +	return result;
> +}
> +
> +static int nt124_port_probe(struct usb_serial_port *port)
> +{
> +	struct usb_interface *interface = port->serial->interface;
> +	struct usb_host_interface *cur_altsetting = interface->cur_altsetting;
> +	struct nt124_private *priv;
> +
> +	priv = devm_kzalloc(&port->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->bInterfaceNumber = cur_altsetting->desc.bInterfaceNumber;
> +
> +	usb_set_serial_port_data(port, priv);
> +
> +	return 0;
> +}
> +
> +static struct usb_serial_driver nt124_device = {
> +	.driver = {
> +		.owner =	THIS_MODULE,
> +		.name =		"nt124",
> +	},
> +	.id_table =		id_table,
> +	.num_ports =		1,
> +	.bulk_in_size =		32,
> +	.bulk_out_size =	32,

Why do you reduce these buffer sizes? They can be bigger than the
endpoint size for increased throughput.

> +	.open =			nt124_open,
> +	.process_read_urb =	nt124_process_read_urb,
> +	.write_bulk_callback =	nt124_write_bulk_callback,
> +	.chars_in_buffer =	nt124_chars_in_buffer,
> +	.throttle =		usb_serial_generic_throttle,
> +	.unthrottle =		usb_serial_generic_unthrottle,
> +	.set_termios =		nt124_set_termios,
> +	.tiocmget =		nt124_tiocmget,
> +	.tiocmset =		nt124_tiocmset,
> +	.dtr_rts =		nt124_dtr_rts,
> +	.break_ctl =		nt124_break_ctl,
> +	.port_probe =		nt124_port_probe,
> +};
> +
> +static struct usb_serial_driver * const serial_drivers[] = {
> +	&nt124_device, NULL
> +};
> +
> +module_usb_serial_driver(serial_drivers, id_table);
> +
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> +MODULE_DESCRIPTION(DRIVER_DESC);
> +MODULE_LICENSE("GPL");

Thanks,
Johan
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