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

Matthias Fuchs
2009-01-15T19:23:18Z

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>
---
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 */
--
1.5.6.3