tty: serial: Add RS422 flag to struct serial_rs485

Add "SER_RS485_MODE_RS422" flag to struct serial_rs485, so that serial
port can switch interface into RS422 if supported by using ioctl command
"TIOCSRS485".

By treating RS422 as a mode of RS485, which means while enabling RS422
there are two flags need to be set (SER_RS485_ENABLED and
SER_RS485_MODE_RS422), it would make things much easier. For example
some places that checks for "SER_RS485_ENABLED" won't need to be rewritten.

Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@moxa.com>
Link: https://lore.kernel.org/r/20231201071554.258607-3-crescentcy.hsieh@moxa.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 1147fb1b39f280746080b5520eb2c34d73ba54c8..d35371c076b2783be5a4784d08b9dcc837b6cd4b 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1370,6 +1370,12 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
                return;
        }
 
+       /* Clear other RS485 flags but SER_RS485_TERMINATE_BUS and return if enabling RS422 */
+       if (rs485->flags & SER_RS485_MODE_RS422) {
+               rs485->flags &= (SER_RS485_ENABLED | SER_RS485_MODE_RS422 | SER_RS485_TERMINATE_BUS);
+               return;
+       }
+
        /* Pick sane settings if the user hasn't */
        if ((supported_flags & (SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND)) &&
            !(rs485->flags & SER_RS485_RTS_ON_SEND) ==

diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
index 6c75ebdd77975e1e8e6dd2ba06edbb906ce06c3c..9086367db0435365689d1f8cbe2a9693958df401 100644 (file)
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -138,6 +138,7 @@ struct serial_icounter_struct {
  * * %SER_RS485_ADDRB          - Enable RS485 addressing mode.
  * * %SER_RS485_ADDR_RECV - Receive address filter (enables @addr_recv). Requires %SER_RS485_ADDRB.
  * * %SER_RS485_ADDR_DEST - Destination address (enables @addr_dest). Requires %SER_RS485_ADDRB.
+ * * %SER_RS485_MODE_RS422     - Enable RS422. Requires %SER_RS485_ENABLED.
  */
 struct serial_rs485 {
        __u32   flags;
@@ -149,6 +150,7 @@ struct serial_rs485 {
 #define SER_RS485_ADDRB                        _BITUL(5)
 #define SER_RS485_ADDR_RECV            _BITUL(6)
 #define SER_RS485_ADDR_DEST            _BITUL(7)
+#define SER_RS485_MODE_RS422           _BITUL(8)
 
        __u32   delay_rts_before_send;
        __u32   delay_rts_after_send;