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

Laurent Pinchart
2009-01-16T09:54:13Z

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

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