| Message ID | 20231113094136.52003-1-crescentcy.hsieh@moxa.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v4] tty: serial: Add RS422 flag to struct serial_rs485 | expand |
Hi, On 11/13/2023 3:41 AM, Crescent CY Hsieh wrote: > 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. > > There are only two things need to be noticed: > > - While enabling RS422, other RS485 flags should not be set. > - RS422 doesn't need to deal with termination, so while disabling RS485 > or enabling RS422, uart_set_rs485_termination() shall return. > > Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@moxa.com> > > [...] > diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h > index 53bc1af67..9086367db 100644 > --- a/include/uapi/linux/serial.h > +++ b/include/uapi/linux/serial.h > @@ -11,6 +11,7 @@ > #ifndef _UAPI_LINUX_SERIAL_H > #define _UAPI_LINUX_SERIAL_H > > +#include <linux/const.h> > #include <linux/types.h> > > #include <linux/tty_flags.h> > @@ -137,17 +138,19 @@ 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. > */ Documentation/driver-api/serial/serial-rs485.rst could also use an update, since it doesn't mention your new flag at all. The documentation as it is also doesn't give a very good idea of what flags userspace might need to set for RS-232 vs RS-422 vs RS-485 (2- or 4-wire). If I compare this to your original patch set [1] for your hardware, then your proposed flag would be used in the following ways, correct? RS-232: rs485->flags = 0 RS-422: rs485->flags = SER_RS485_ENABLED|SER_RS485_MODE_RS422 RS-485 (2-wire half-duplex): rs485->flags = SER_RS485_ENABLED RS-485 (4-wire full-duplex): rs485->flags = SER_RS485_ENABLED|SER_RS485_RX_DURING_TX In iot2040_rs485_config in 8250_exar.c [2] we already seem to have: RS-232: rs485->flags = 0 RS-422: rs485->flags = SER_RS485_ENABLED|SER_RS485_RX_DURING_TX RS-485 (2-wire half-duplex?): rs485->flags = SER_RS485_ENABLED This would seem to create an inconsistency in this API. I've also been trying to get a driver for NI's serial hardware upstream [3]; we have "RS-485" products that can do both RS-422/RS-485, and also have use of functionality to toggle between the two modes, so-- whichever way this flag goes-- I'd like to be consistent with how other drivers do it. [1] https://lore.kernel.org/linux-serial/20231018091739.10125-7-crescentcy.hsieh@moxa.com/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/8250/8250_exar.c?h=v6.6#n459 [3] https://lore.kernel.org/linux-serial/20231023210458.447779-3-brenda.streiff@ni.com/
Hi, On 15.11.23 03:50, Brenda Streiff wrote: > > Documentation/driver-api/serial/serial-rs485.rst could also use an update, > since it doesn't mention your new flag at all. > > The documentation as it is also doesn't give a very good idea of what flags > userspace might need to set for RS-232 vs RS-422 vs RS-485 (2- or 4-wire). > > If I compare this to your original patch set [1] for your hardware, then > your proposed flag would be used in the following ways, correct? > > RS-232: rs485->flags = 0 > RS-422: rs485->flags = SER_RS485_ENABLED|SER_RS485_MODE_RS422 > RS-485 (2-wire half-duplex): rs485->flags = SER_RS485_ENABLED > RS-485 (4-wire full-duplex): rs485->flags = SER_RS485_ENABLED|SER_RS485_RX_DURING_TX > > In iot2040_rs485_config in 8250_exar.c [2] we already seem to have: > RS-232: rs485->flags = 0 > RS-422: rs485->flags = SER_RS485_ENABLED|SER_RS485_RX_DURING_TX > RS-485 (2-wire half-duplex?): rs485->flags = SER_RS485_ENABLED > > This would seem to create an inconsistency in this API. > We can adjust 8250_exar later to also honor SER_RS485_MODE_RS422. But yes, we have to also keep the current logic (i.e. set the RS422 mode if SER_RS485_ENABLED|SER_RS485_RX_DURING_TX is set) for backward compatibility. Regards, Lino
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 831d03361..777f091a4 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1376,6 +1376,13 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4 return; } + /* Clear other RS485 flags and return if enabling RS422 */ + if (rs485->flags & SER_RS485_MODE_RS422) { + memset(rs485, 0, sizeof(*rs485)); + rs485->flags |= (SER_RS485_ENABLED | SER_RS485_MODE_RS422); + 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) == @@ -1400,7 +1407,9 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4 static void uart_set_rs485_termination(struct uart_port *port, const struct serial_rs485 *rs485) { - if (!(rs485->flags & SER_RS485_ENABLED)) + /* Return while disabling RS485 or enabling RS422 */ + if (!(rs485->flags & SER_RS485_ENABLED) || + (rs485->flags & SER_RS485_ENABLED && rs485->flags & SER_RS485_MODE_RS422)) return; gpiod_set_value_cansleep(port->rs485_term_gpio, diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h index 53bc1af67..9086367db 100644 --- a/include/uapi/linux/serial.h +++ b/include/uapi/linux/serial.h @@ -11,6 +11,7 @@ #ifndef _UAPI_LINUX_SERIAL_H #define _UAPI_LINUX_SERIAL_H +#include <linux/const.h> #include <linux/types.h> #include <linux/tty_flags.h> @@ -137,17 +138,19 @@ 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; -#define SER_RS485_ENABLED (1 << 0) -#define SER_RS485_RTS_ON_SEND (1 << 1) -#define SER_RS485_RTS_AFTER_SEND (1 << 2) -#define SER_RS485_RX_DURING_TX (1 << 4) -#define SER_RS485_TERMINATE_BUS (1 << 5) -#define SER_RS485_ADDRB (1 << 6) -#define SER_RS485_ADDR_RECV (1 << 7) -#define SER_RS485_ADDR_DEST (1 << 8) +#define SER_RS485_ENABLED _BITUL(0) +#define SER_RS485_RTS_ON_SEND _BITUL(1) +#define SER_RS485_RTS_AFTER_SEND _BITUL(2) +#define SER_RS485_RX_DURING_TX _BITUL(3) +#define SER_RS485_TERMINATE_BUS _BITUL(4) +#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;
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. There are only two things need to be noticed: - While enabling RS422, other RS485 flags should not be set. - RS422 doesn't need to deal with termination, so while disabling RS485 or enabling RS422, uart_set_rs485_termination() shall return. Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@moxa.com> --- Changes from v3 to v4: - Include 'linux/const.h' header in '/include/uapi/linux/serial.h' - Replace BIT() with _BITUL() which defined in '/include/uapi/linux/const.h' Changes from v2 to v3: - Remove "SER_RS422_ENABLED" flag from legacy flags. - Revise "SER_RS422_ENABLED" into "SER_RS485_MODE_RS422". - Remove the code which checks the conflicts between SER_RS485_ENABLED and SER_RS422_ENABLED. - Add return check in uart_set_rs485_termination(). Changes from v1 to v2: - Revise the logic that checks whether RS422/RS485 are enabled simultaneously. v3: https://lore.kernel.org/all/20231108060719.11775-1-crescentcy.hsieh@moxa.com/ v2: https://lore.kernel.org/all/20231101064404.45711-1-crescentcy.hsieh@moxa.com/ v1: https://lore.kernel.org/all/20231030053632.5109-1-crescentcy.hsieh@moxa.com/ --- drivers/tty/serial/serial_core.c | 11 ++++++++++- include/uapi/linux/serial.h | 19 +++++++++++-------- 2 files changed, 21 insertions(+), 9 deletions(-)