Commit 974e2f6a authored by Jarkko Sonninen's avatar Jarkko Sonninen Committed by Johan Hovold
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USB: serial: xr: add TIOCGRS485 and TIOCSRS485 ioctls 



Exar devices like XR21B1411 can control an RS485 transceiver by
automatically asserting the RTS#/RS485 pin before sending data
and deasserting it when the last stop bit has been transmitted.
The polarity of the RST#/RS485 signal is configurable and the
hardware also supports half-duplex turn-around delay and
address matching mode.

Add support for enabling and disabling RS-485 mode and
configuring the RST#/RS485 signal polarity using the TIOCGRS485
and TIOCSRS485 ioctls. Support for half-duplex turn-around delay
and address matching mode are left unimplemented for now.

User enables RS-485 mode by setting SER_RS485_ENABLED flag in
struct serial_rs485 flags. User should also set either
SER_RS485_RTS_ON_SEND or SER_RS485_RTS_AFTER_SEND to select the
behaviour of the RTS#/RS485 pin. Setting SER_RS485_RTS_ON_SEND
will drive RTS#/RS485 low during transmission.

Signed-off-by: default avatarJarkko Sonninen <kasper@iki.fi>
[ johan: let SER_RS485_RTS_ON_SEND determine SER_RS485_RTS_AFTER_SEND ]
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent fdf0eaf1

drivers/usb/serial/xr_serial.c

+88 −1
Original line number Diff line number Diff line
@@ -93,6 +93,7 @@ struct xr_txrx_clk_mask { 
#define XR_GPIO_MODE_SEL_DTR_DSR	0x2

#define XR_GPIO_MODE_SEL_RS485		0x3

#define XR_GPIO_MODE_SEL_RS485_ADDR	0x4

#define XR_GPIO_MODE_RS485_TX_H		0x8

#define XR_GPIO_MODE_TX_TOGGLE		0x100

#define XR_GPIO_MODE_RX_TOGGLE		0x200
@@ -237,6 +238,7 @@ static const struct xr_type xr_types[] = { 
struct xr_data {

	const struct xr_type *type;

	u8 channel;			/* zero-based index or interface number */

	struct serial_rs485 rs485;

};



static int xr_set_reg(struct usb_serial_port *port, u8 channel, u16 reg, u16 val)
@@ -629,6 +631,7 @@ static void xr_set_flow_mode(struct tty_struct *tty, 
	struct xr_data *data = usb_get_serial_port_data(port);

	const struct xr_type *type = data->type;

	u16 flow, gpio_mode;

	bool rs485_enabled;

	int ret;



	ret = xr_get_reg_uart(port, type->gpio_mode, &gpio_mode);
@@ -645,7 +648,17 @@ static void xr_set_flow_mode(struct tty_struct *tty, 
	/* Set GPIO mode for controlling the pins manually by default. */

	gpio_mode &= ~XR_GPIO_MODE_SEL_MASK;



	if (C_CRTSCTS(tty) && C_BAUD(tty) != B0) {

	rs485_enabled = !!(data->rs485.flags & SER_RS485_ENABLED);

	if (rs485_enabled) {

		dev_dbg(&port->dev, "Enabling RS-485\n");

		gpio_mode |= XR_GPIO_MODE_SEL_RS485;

		if (data->rs485.flags & SER_RS485_RTS_ON_SEND)

			gpio_mode &= ~XR_GPIO_MODE_RS485_TX_H;

		else

			gpio_mode |= XR_GPIO_MODE_RS485_TX_H;

	}



	if (C_CRTSCTS(tty) && C_BAUD(tty) != B0 && !rs485_enabled) {

		dev_dbg(&port->dev, "Enabling hardware flow ctrl\n");

		gpio_mode |= XR_GPIO_MODE_SEL_RTS_CTS;

		flow = XR_UART_FLOW_MODE_HW;
@@ -809,6 +822,79 @@ static void xr_cdc_set_line_coding(struct tty_struct *tty, 
	kfree(lc);

}



static void xr_sanitize_serial_rs485(struct serial_rs485 *rs485)

{

	if (!(rs485->flags & SER_RS485_ENABLED)) {

		memset(rs485, 0, sizeof(*rs485));

		return;

	}



	/* RTS always toggles after TX */

	if (rs485->flags & SER_RS485_RTS_ON_SEND)

		rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;

	else

		rs485->flags |= SER_RS485_RTS_AFTER_SEND;



	/* Only the flags are implemented at the moment */

	rs485->flags &= SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |

			SER_RS485_RTS_AFTER_SEND;

	rs485->delay_rts_before_send = 0;

	rs485->delay_rts_after_send = 0;

	memset(rs485->padding, 0, sizeof(rs485->padding));

}



static int xr_get_rs485_config(struct tty_struct *tty,

			       struct serial_rs485 __user *argp)

{

	struct usb_serial_port *port = tty->driver_data;

	struct xr_data *data = usb_get_serial_port_data(port);



	down_read(&tty->termios_rwsem);

	if (copy_to_user(argp, &data->rs485, sizeof(data->rs485))) {

		up_read(&tty->termios_rwsem);

		return -EFAULT;

	}

	up_read(&tty->termios_rwsem);



	return 0;

}



static int xr_set_rs485_config(struct tty_struct *tty,

			       struct serial_rs485 __user *argp)

{

	struct usb_serial_port *port = tty->driver_data;

	struct xr_data *data = usb_get_serial_port_data(port);

	struct serial_rs485 rs485;



	if (copy_from_user(&rs485, argp, sizeof(rs485)))

		return -EFAULT;

	xr_sanitize_serial_rs485(&rs485);



	down_write(&tty->termios_rwsem);

	data->rs485 = rs485;

	xr_set_flow_mode(tty, port, NULL);

	up_write(&tty->termios_rwsem);



	if (copy_to_user(argp, &rs485, sizeof(rs485)))

		return -EFAULT;



	return 0;

}



static int xr_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)

{

	void __user *argp = (void __user *)arg;



	switch (cmd) {

	case TIOCGRS485:

		return xr_get_rs485_config(tty, argp);

	case TIOCSRS485:

		return xr_set_rs485_config(tty, argp);

	}



	return -ENOIOCTLCMD;

}



static void xr_set_termios(struct tty_struct *tty,

			   struct usb_serial_port *port,

			   const struct ktermios *old_termios)
@@ -1010,6 +1096,7 @@ static struct usb_serial_driver xr_device = { 
	.set_termios		= xr_set_termios,

	.tiocmget		= xr_tiocmget,

	.tiocmset		= xr_tiocmset,

	.ioctl			= xr_ioctl,

	.dtr_rts		= xr_dtr_rts

};