Re: [PATCH V3] serial: Add ioctl to enable auto rs485 mode with some Exar UARTs

[Laurent Pinchart <laurentp@cse-semaphore.com>]

On Thursday 15 January 2009 20:23:15 Matthias Fuchs wrote:
> Some Exar UARTs support an auto rs485 mode. In this mode
> the UART's RTS# pin is activated during transmitting and
> can be used to enable a rs485 line driver. This has nothing
> to do with attempts to do this by manually asserting/
> deasserting handshake lines in software.
>
> Signed-off-by: Matthias Fuchs <mfuchs@ma-fu.de>

Acked-by: Laurent Pinchart <laurentp@cse-semaphore.com>

> ---
>  drivers/serial/8250.c      |   70
> ++++++++++++++++++++++++++++++++++++++++++++ include/linux/serial_reg.h |  
>  1 +
>  2 files changed, 71 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
> index 0d934bf..9c986bd 100644
> --- a/drivers/serial/8250.c
> +++ b/drivers/serial/8250.c
> @@ -2580,6 +2580,75 @@ serial8250_type(struct uart_port *port)
>  	return uart_config[type].name;
>  }
>
> +static int
> +serial8250_ioctl_port(struct uart_port *port,
> +		      unsigned int cmd, unsigned long arg)
> +{
> +	struct uart_8250_port *up = (struct uart_8250_port *)port;
> +	unsigned long flags;
> +
> +	switch (cmd) {
> +	case TIOCSRS485:
> +	{
> +		struct serial_rs485 rs485ctrl;
> +		unsigned char fctr, lcr;
> +
> +		if (port->type != PORT_16850)
> +			return -ENOTTY;
> +
> +		if (copy_from_user(&rs485ctrl,
> +				   (struct serial_rs485 *)arg,
> +				   sizeof(rs485ctrl)))
> +			return -EFAULT;
> +
> +		spin_lock_irqsave(&up->port.lock, flags);
> +		lcr = serial_inp(up, UART_LCR);
> +		serial_outp(up, UART_LCR, 0xbf);
> +		fctr = serial_inp(up, UART_FCTR);
> +		if (rs485ctrl.flags & SER_RS485_ENABLED)
> +			fctr |= UART_FCTR_RS485;
> +		else
> +			fctr &= ~UART_FCTR_RS485;
> +		serial_outp(up, UART_FCTR, fctr);
> +		serial_outp(up, UART_LCR, lcr);
> +		spin_unlock_irqrestore(&up->port.lock, flags);
> +		return 0;
> +	}
> +
> +	case TIOCGRS485:
> +	{
> +		struct serial_rs485 rs485ctrl;
> +		unsigned char lcr;
> +
> +		if (port->type != PORT_16850)
> +			return -ENOTTY;
> +
> +		memset(&rs485ctrl, 0, sizeof(rs485ctrl));
> +
> +		spin_lock_irqsave(&up->port.lock, flags);
> +		lcr = serial_inp(up, UART_LCR);
> +		serial_outp(up, UART_LCR, 0xbf);
> +		if (serial_inp(up, UART_FCTR) & UART_FCTR_RS485)
> +			rs485ctrl.flags = SER_RS485_ENABLED;
> +		else
> +			rs485ctrl.flags = 0;
> +		serial_outp(up, UART_LCR, lcr);
> +		spin_unlock_irqrestore(&up->port.lock, flags);
> +
> +		if (copy_to_user((struct serial_rs485 *)arg,
> +				 &rs485ctrl,
> +				 sizeof(rs485ctrl)))
> +			return -EFAULT;
> +		return 0;
> +	}
> +
> +	default:
> +		return -ENOIOCTLCMD;
> +	}
> +
> +	return 0;
> +}
> +
>  static struct uart_ops serial8250_pops = {
>  	.tx_empty	= serial8250_tx_empty,
>  	.set_mctrl	= serial8250_set_mctrl,
> @@ -2598,6 +2667,7 @@ static struct uart_ops serial8250_pops = {
>  	.request_port	= serial8250_request_port,
>  	.config_port	= serial8250_config_port,
>  	.verify_port	= serial8250_verify_port,
> +	.ioctl		= serial8250_ioctl_port,
>  #ifdef CONFIG_CONSOLE_POLL
>  	.poll_get_char = serial8250_get_poll_char,
>  	.poll_put_char = serial8250_put_poll_char,
> diff --git a/include/linux/serial_reg.h b/include/linux/serial_reg.h
> index 96c0d93..086c3e2 100644
> --- a/include/linux/serial_reg.h
> +++ b/include/linux/serial_reg.h
> @@ -191,6 +191,7 @@
>  #define UART_FCTR_RTS_8DELAY	0x03
>  #define UART_FCTR_IRDA		0x04  /* IrDa data encode select */
>  #define UART_FCTR_TX_INT	0x08  /* Tx interrupt type select */
> +#define UART_FCTR_RS485		0x08  /* Auto RS485 mode */
>  #define UART_FCTR_TRGA		0x00  /* Tx/Rx 550 trigger table select */
>  #define UART_FCTR_TRGB		0x10  /* Tx/Rx 650 trigger table select */
>  #define UART_FCTR_TRGC		0x20  /* Tx/Rx 654 trigger table select */

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75