[RFC PATCH 5/7] serial: termbits: ADDRB to indicate 9th bit addressing mode

[RFC PATCH 5/7] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Ilpo Järvinen]

Add ADDRB to termbits to indicate 9th bit addressing mode.
This change is necessary for supporting devices with RS485
multipoint addressing [*]. A later patch in the patch series
adds support for Synopsys Designware UART capable for 9th bit
addressing mode. In this mode, 9th bit is used to indicate an
address (byte) within the communication line. The 9th bit
addressing mode is selected using ADDRB introduced by an earlier
patch.

[*] Technically, RS485 is just an electronic spec and does not
itself specify the 9th bit addressing mode but 9th bit seems
at least "semi-standard" way to do addressing with RS485.

Cc: linux-api@vger.kernel.org
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-alpha@vger.kernel.org
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 arch/alpha/include/uapi/asm/termbits.h   | 1 +
 arch/mips/include/uapi/asm/termbits.h    | 1 +
 arch/parisc/include/uapi/asm/termbits.h  | 1 +
 arch/powerpc/include/uapi/asm/termbits.h | 1 +
 arch/sparc/include/uapi/asm/termbits.h   | 1 +
 drivers/tty/amiserial.c                  | 6 +++++-
 drivers/tty/moxa.c                       | 1 +
 drivers/tty/mxser.c                      | 1 +
 drivers/tty/serial/serial_core.c         | 2 ++
 drivers/tty/tty_ioctl.c                  | 2 ++
 drivers/usb/serial/usb-serial.c          | 5 +++--
 include/uapi/asm-generic/termbits.h      | 1 +
 12 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/termbits.h b/arch/alpha/include/uapi/asm/termbits.h
index 4575ba34a0ea..285169c794ec 100644
--- a/arch/alpha/include/uapi/asm/termbits.h
+++ b/arch/alpha/include/uapi/asm/termbits.h
@@ -180,6 +180,7 @@ struct ktermios {
 #define HUPCL	00040000
 
 #define CLOCAL	00100000
+#define ADDRB	010000000		/* address bit */
 #define CMSPAR	  010000000000		/* mark or space (stick) parity */
 #define CRTSCTS	  020000000000		/* flow control */
 
diff --git a/arch/mips/include/uapi/asm/termbits.h b/arch/mips/include/uapi/asm/termbits.h
index dfeffba729b7..e7ea31cfec78 100644
--- a/arch/mips/include/uapi/asm/termbits.h
+++ b/arch/mips/include/uapi/asm/termbits.h
@@ -181,6 +181,7 @@ struct ktermios {
 #define	 B3000000 0010015
 #define	 B3500000 0010016
 #define	 B4000000 0010017
+#define ADDRB	  0020000	/* address bit */
 #define CIBAUD	  002003600000	/* input baud rate */
 #define CMSPAR	  010000000000	/* mark or space (stick) parity */
 #define CRTSCTS	  020000000000	/* flow control */
diff --git a/arch/parisc/include/uapi/asm/termbits.h b/arch/parisc/include/uapi/asm/termbits.h
index 40e920f8d683..629be061f5d5 100644
--- a/arch/parisc/include/uapi/asm/termbits.h
+++ b/arch/parisc/include/uapi/asm/termbits.h
@@ -158,6 +158,7 @@ struct ktermios {
 #define  B3000000 0010015
 #define  B3500000 0010016
 #define  B4000000 0010017
+#define ADDRB	  0020000		/* address bit */
 #define CIBAUD    002003600000		/* input baud rate */
 #define CMSPAR    010000000000          /* mark or space (stick) parity */
 #define CRTSCTS   020000000000          /* flow control */
diff --git a/arch/powerpc/include/uapi/asm/termbits.h b/arch/powerpc/include/uapi/asm/termbits.h
index ed18bc61f63d..1b778ac562a4 100644
--- a/arch/powerpc/include/uapi/asm/termbits.h
+++ b/arch/powerpc/include/uapi/asm/termbits.h
@@ -171,6 +171,7 @@ struct ktermios {
 #define HUPCL	00040000
 
 #define CLOCAL	00100000
+#define ADDRB	00200000		/* address bit */
 #define CMSPAR	  010000000000		/* mark or space (stick) parity */
 #define CRTSCTS	  020000000000		/* flow control */
 
diff --git a/arch/sparc/include/uapi/asm/termbits.h b/arch/sparc/include/uapi/asm/termbits.h
index ce5ad5d0f105..4ad60c4acf65 100644
--- a/arch/sparc/include/uapi/asm/termbits.h
+++ b/arch/sparc/include/uapi/asm/termbits.h
@@ -200,6 +200,7 @@ struct ktermios {
 #define B3000000  0x00001011
 #define B3500000  0x00001012
 #define B4000000  0x00001013  */
+#define ADDRB	  0x00002000  /* address bit */
 #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
 #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
 #define CRTSCTS	  0x80000000  /* flow control */
diff --git a/drivers/tty/amiserial.c b/drivers/tty/amiserial.c
index 533d02b38e02..3ca97007bd6e 100644
--- a/drivers/tty/amiserial.c
+++ b/drivers/tty/amiserial.c
@@ -1175,7 +1175,11 @@ static void rs_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
 {
 	struct serial_state *info = tty->driver_data;
 	unsigned long flags;
-	unsigned int cflag = tty->termios.c_cflag;
+	unsigned int cflag;
+
+	tty->termios.c_cflag &= ~ADDRB;
+
+	cflag = tty->termios.c_cflag;
 
 	change_speed(tty, info, old_termios);
 
diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index f3c72ab1476c..07cd88152d58 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -2050,6 +2050,7 @@ static int MoxaPortSetTermio(struct moxa_port *port, struct ktermios *termio,
 
 	ofsAddr = port->tableAddr;
 
+	termio->c_cflag &= ~ADDRB;
 	mode = termio->c_cflag & CSIZE;
 	if (mode == CS5)
 		mode = MX_CS5;
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 836c9eca2946..220676363a07 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -577,6 +577,7 @@ static void mxser_change_speed(struct tty_struct *tty, struct ktermios *old_term
 	struct mxser_port *info = tty->driver_data;
 	unsigned cflag, cval;
 
+	tty->termios.c_cflag &= ~ADDRB;
 	cflag = tty->termios.c_cflag;
 
 	if (mxser_set_baud(tty, tty_get_baud_rate(tty))) {
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 846192a7b4bf..8ab88293c917 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1489,6 +1489,8 @@ static void uart_set_termios(struct tty_struct *tty,
 		goto out;
 	}
 
+	tty->termios.c_cflag &= ~ADDRB;
+
 	uart_change_speed(tty, state, old_termios);
 	/* reload cflag from termios; port driver may have overridden flags */
 	cflag = tty->termios.c_cflag;
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 63181925ec1a..934037d78868 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -319,6 +319,8 @@ unsigned char tty_get_frame_size(unsigned int cflag)
 		bits++;
 	if (cflag & PARENB)
 		bits++;
+	if (cflag & ADDRB)
+		bits++;
 
 	return bits;
 }
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 24101bd7fcad..44b73aea80bb 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -525,9 +525,10 @@ static void serial_set_termios(struct tty_struct *tty, struct ktermios *old)
 
 	dev_dbg(&port->dev, "%s\n", __func__);
 
-	if (port->serial->type->set_termios)
+	if (port->serial->type->set_termios) {
+		tty->termios.c_cflag &= ~ADDRB;
 		port->serial->type->set_termios(tty, port, old);
-	else
+	} else
 		tty_termios_copy_hw(&tty->termios, old);
 }
 
diff --git a/include/uapi/asm-generic/termbits.h b/include/uapi/asm-generic/termbits.h
index 2fbaf9ae89dd..5f5228329d45 100644
--- a/include/uapi/asm-generic/termbits.h
+++ b/include/uapi/asm-generic/termbits.h
@@ -157,6 +157,7 @@ struct ktermios {
 #define  B3000000 0010015
 #define  B3500000 0010016
 #define  B4000000 0010017
+#define ADDRB     0020000	/* address bit */
 #define CIBAUD	  002003600000	/* input baud rate */
 #define CMSPAR	  010000000000	/* mark or space (stick) parity */
 #define CRTSCTS	  020000000000	/* flow control */
-- 
2.30.2

[RFC PATCH 6/7] serial: General support for multipoint addresses

[Ilpo Järvinen]

This patch adds generic support for serial multipoint
addressing. Two new ioctls are added. TIOCSADDR is used to
indicate the destination/receive address. TIOCGADDR returns
the current address in use. The driver should implement
set_addr and get_addr to support addressing mode.

Adjust ADDRB clearing to happen only if driver does not provide
set_addr (=the driver doesn't support address mode).

This change is necessary for supporting devices with RS485
multipoint addressing [*]. A following patch in the patch series
adds support for Synopsys Designware UART capable for 9th bit
addressing mode. In this mode, 9th bit is used to indicate an
address (byte) within the communication line. The 9th bit
addressing mode is selected using ADDRB introduced by the
previous patch.

Transmit addresses / receiver filter are specified by setting
the flags SER_ADDR_DEST and/or SER_ADDR_RECV. When the user
supplies the transmit address, in the 9bit addressing mode it is
sent out immediately with the 9th bit set to 1. After that, the
subsequent normal data bytes are sent with 9th bit as 0 and they
are intended to the device with the given address. It is up to
receiver to enforce the filter using SER_ADDR_RECV. When userspace
has supplied the receive address, the driver is expected to handle
the matching of the address and only data with that address is
forwarded to the user. Both SER_ADDR_DEST and SER_ADDR_RECV can
be given at the same time in a single call if the addresses are
the same.

The user can clear the receive filter with SER_ADDR_RECV_CLEAR.

[*] Technically, RS485 is just an electronic spec and does not
itself specify the 9th bit addressing mode but 9th bit seems
at least "semi-standard" way to do addressing with RS485.

Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Richard Henderson <rth-hL46jP5Bxq7R7s880joybQ@public.gmane.org>
Cc: Ivan Kokshaysky <ink-biIs/Y0ymYJMZLIVYojuPNP0rXTJTi09@public.gmane.org>
Cc: Matt Turner <mattst88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-alpha-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Thomas Bogendoerfer <tsbogend-I1c7kopa9pxLokYuJOExCg@public.gmane.org>
Cc: linux-mips-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: "James E.J. Bottomley" <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org>
Cc: Helge Deller <deller-Mmb7MZpHnFY@public.gmane.org>
Cc: linux-parisc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
Cc: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Cc: Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
Cc: linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
Cc: Yoshinori Sato <ysato-Rn4VEauK+AKRv+LV9MX5uooqe+aC9MnS@public.gmane.org>
Cc: Rich Felker <dalias-8zAoT0mYgF4@public.gmane.org>
Cc: linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: "David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
Cc: sparclinux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Chris Zankel <chris-YvXeqwSYzG2sTnJN9+BGXg@public.gmane.org>
Cc: Max Filippov <jcmvbkbc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-xtensa-PjhNF2WwrV/0Sa2dR60CXw@public.gmane.org
Cc: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Cc: linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 .../driver-api/serial/serial-rs485.rst        | 23 ++++++-
 arch/alpha/include/uapi/asm/ioctls.h          |  3 +
 arch/mips/include/uapi/asm/ioctls.h           |  3 +
 arch/parisc/include/uapi/asm/ioctls.h         |  3 +
 arch/powerpc/include/uapi/asm/ioctls.h        |  3 +
 arch/sh/include/uapi/asm/ioctls.h             |  3 +
 arch/sparc/include/uapi/asm/ioctls.h          |  3 +
 arch/xtensa/include/uapi/asm/ioctls.h         |  3 +
 drivers/tty/serial/8250/8250_core.c           |  2 +
 drivers/tty/serial/serial_core.c              | 62 ++++++++++++++++++-
 include/linux/serial_core.h                   |  6 ++
 include/uapi/asm-generic/ioctls.h             |  3 +
 include/uapi/linux/serial.h                   |  8 +++
 13 files changed, 123 insertions(+), 2 deletions(-)

diff --git a/Documentation/driver-api/serial/serial-rs485.rst b/Documentation/driver-api/serial/serial-rs485.rst
index 6bc824f948f9..2f45f007fa5b 100644
--- a/Documentation/driver-api/serial/serial-rs485.rst
+++ b/Documentation/driver-api/serial/serial-rs485.rst
@@ -95,7 +95,28 @@ RS485 Serial Communications
 		/* Error handling. See errno. */
 	}
 
-5. References
+5. Multipoint Addressing
+========================
+
+   The Linux kernel provides serial_addr structure to handle addressing within
+   multipoint serial communications line such as RS485. 9th bit addressiong mode
+   is enabled by adding ADDRB flag in termios c_cflag.
+
+   Serial core calls device specific set/get_addr in response to TIOCSADDR and
+   TIOCGADDR ioctls with a pointer to serial_addr. Destination and receive
+   address can be specified using serial_addr flags field. Receive address may
+   also be cleared using flags. Once an address is set, the communication
+   can occur only with the particular device and other peers are filtered out.
+   It is left up to the receiver side to enforce the filtering.
+
+   Address flags:
+	- SER_ADDR_RECV: Receive (filter) address.
+	- SER_ADDR_RECV_CLEAR: Clear receive filter (only for TIOCSADDR).
+	- SER_ADDR_DEST: Destination address.
+
+   Note: not all devices supporting RS485 support multipoint addressing.
+
+6. References
 =============
 
  [1]	include/uapi/linux/serial.h
diff --git a/arch/alpha/include/uapi/asm/ioctls.h b/arch/alpha/include/uapi/asm/ioctls.h
index 971311605288..500cab3e1d6b 100644
--- a/arch/alpha/include/uapi/asm/ioctls.h
+++ b/arch/alpha/include/uapi/asm/ioctls.h
@@ -125,4 +125,7 @@
 #define TIOCMIWAIT	0x545C	/* wait for a change on serial input line(s) */
 #define TIOCGICOUNT	0x545D	/* read serial port inline interrupt counts */
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 #endif /* _ASM_ALPHA_IOCTLS_H */
diff --git a/arch/mips/include/uapi/asm/ioctls.h b/arch/mips/include/uapi/asm/ioctls.h
index 16aa8a766aec..3859dc46857e 100644
--- a/arch/mips/include/uapi/asm/ioctls.h
+++ b/arch/mips/include/uapi/asm/ioctls.h
@@ -96,6 +96,9 @@
 #define TIOCGISO7816	_IOR('T', 0x42, struct serial_iso7816)
 #define TIOCSISO7816	_IOWR('T', 0x43, struct serial_iso7816)
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 /* I hope the range from 0x5480 on is free ... */
 #define TIOCSCTTY	0x5480		/* become controlling tty */
 #define TIOCGSOFTCAR	0x5481
diff --git a/arch/parisc/include/uapi/asm/ioctls.h b/arch/parisc/include/uapi/asm/ioctls.h
index 82d1148c6379..62337743db64 100644
--- a/arch/parisc/include/uapi/asm/ioctls.h
+++ b/arch/parisc/include/uapi/asm/ioctls.h
@@ -86,6 +86,9 @@
 #define TIOCSTOP	0x5462
 #define TIOCSLTC	0x5462
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 /* Used for packet mode */
 #define TIOCPKT_DATA		 0
 #define TIOCPKT_FLUSHREAD	 1
diff --git a/arch/powerpc/include/uapi/asm/ioctls.h b/arch/powerpc/include/uapi/asm/ioctls.h
index 2c145da3b774..84fd69ac366a 100644
--- a/arch/powerpc/include/uapi/asm/ioctls.h
+++ b/arch/powerpc/include/uapi/asm/ioctls.h
@@ -120,4 +120,7 @@
 #define TIOCMIWAIT	0x545C	/* wait for a change on serial input line(s) */
 #define TIOCGICOUNT	0x545D	/* read serial port inline interrupt counts */
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 #endif	/* _ASM_POWERPC_IOCTLS_H */
diff --git a/arch/sh/include/uapi/asm/ioctls.h b/arch/sh/include/uapi/asm/ioctls.h
index 11866d4f60e1..f82966b7dba2 100644
--- a/arch/sh/include/uapi/asm/ioctls.h
+++ b/arch/sh/include/uapi/asm/ioctls.h
@@ -113,4 +113,7 @@
 #define TIOCMIWAIT	_IO('T', 92) /* 0x545C */	/* wait for a change on serial input line(s) */
 #define TIOCGICOUNT	0x545D	/* read serial port inline interrupt counts */
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 #endif /* __ASM_SH_IOCTLS_H */
diff --git a/arch/sparc/include/uapi/asm/ioctls.h b/arch/sparc/include/uapi/asm/ioctls.h
index 7fd2f5873c9e..e44624c67c79 100644
--- a/arch/sparc/include/uapi/asm/ioctls.h
+++ b/arch/sparc/include/uapi/asm/ioctls.h
@@ -125,6 +125,9 @@
 #define TIOCMIWAIT	0x545C /* Wait for change on serial input line(s) */
 #define TIOCGICOUNT	0x545D /* Read serial port inline interrupt counts */
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 /* Kernel definitions */
 
 /* Used for packet mode */
diff --git a/arch/xtensa/include/uapi/asm/ioctls.h b/arch/xtensa/include/uapi/asm/ioctls.h
index 6d4a87296c95..759ca9377f2a 100644
--- a/arch/xtensa/include/uapi/asm/ioctls.h
+++ b/arch/xtensa/include/uapi/asm/ioctls.h
@@ -127,4 +127,7 @@
 #define TIOCMIWAIT	_IO('T', 92) /* wait for a change on serial input line(s) */
 #define TIOCGICOUNT	0x545D	/* read serial port inline interrupt counts */
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 #endif /* _XTENSA_IOCTLS_H */
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 01d30f6ed8fb..f67bc3b76f65 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1008,6 +1008,8 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 		uart->port.rs485	= up->port.rs485;
 		uart->rs485_start_tx	= up->rs485_start_tx;
 		uart->rs485_stop_tx	= up->rs485_stop_tx;
+		uart->port.set_addr	= up->port.set_addr;
+		uart->port.get_addr	= up->port.get_addr;
 		uart->dma		= up->dma;
 
 		/* Take tx_loadsz from fifosize if it wasn't set separately */
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 8ab88293c917..8235f696d073 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1346,6 +1346,56 @@ static int uart_set_iso7816_config(struct uart_port *port,
 	return 0;
 }
 
+static int uart_set_addr(struct uart_port *port,
+			 struct serial_addr __user *serial_addr_user)
+{
+	struct serial_addr addr;
+	unsigned long flags;
+	int ret;
+
+	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
+		return -EFAULT;
+
+	spin_lock_irqsave(&port->lock, flags);
+	if (port->set_addr)
+		ret = port->set_addr(port, &addr);
+	else
+		ret = -EINVAL;
+	spin_unlock_irqrestore(&port->lock, flags);
+	if (ret)
+		return ret;
+
+	if (copy_to_user(serial_addr_user, &addr, sizeof(addr)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int uart_get_addr(struct uart_port *port,
+			 struct serial_addr __user *serial_addr_user)
+{
+	struct serial_addr addr;
+	unsigned long flags;
+	int ret;
+
+	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
+		return -EFAULT;
+
+	spin_lock_irqsave(&port->lock, flags);
+	if (port->get_addr)
+		ret = port->get_addr(port, &addr);
+	else
+		ret = -EINVAL;
+	spin_unlock_irqrestore(&port->lock, flags);
+	if (ret)
+		return ret;
+
+	if (copy_to_user(serial_addr_user, &addr, sizeof(addr)))
+		return -EFAULT;
+
+	return 0;
+}
+
 /*
  * Called via sys_ioctl.  We can use spin_lock_irq() here.
  */
@@ -1423,6 +1473,15 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 	case TIOCGISO7816:
 		ret = uart_get_iso7816_config(state->uart_port, uarg);
 		break;
+
+	case TIOCSADDR:
+		ret = uart_set_addr(uport, uarg);
+		break;
+
+	case TIOCGADDR:
+		ret = uart_get_addr(uport, uarg);
+		break;
+
 	default:
 		if (uport->ops->ioctl)
 			ret = uport->ops->ioctl(uport, cmd, arg);
@@ -1489,7 +1548,8 @@ static void uart_set_termios(struct tty_struct *tty,
 		goto out;
 	}
 
-	tty->termios.c_cflag &= ~ADDRB;
+	if (!uport->set_addr)
+		tty->termios.c_cflag &= ~ADDRB;
 
 	uart_change_speed(tty, state, old_termios);
 	/* reload cflag from termios; port driver may have overridden flags */
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 31f7fe527395..ebe1d0ec11d8 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -135,6 +135,12 @@ struct uart_port {
 						struct serial_rs485 *rs485);
 	int			(*iso7816_config)(struct uart_port *,
 						  struct serial_iso7816 *iso7816);
+
+	int			(*set_addr)(struct uart_port *p,
+					    struct serial_addr *addr);
+	int			(*get_addr)(struct uart_port *p,
+					    struct serial_addr *addr);
+
 	unsigned int		irq;			/* irq number */
 	unsigned long		irqflags;		/* irq flags  */
 	unsigned int		uartclk;		/* base uart clock */
diff --git a/include/uapi/asm-generic/ioctls.h b/include/uapi/asm-generic/ioctls.h
index cdc9f4ca8c27..689743366091 100644
--- a/include/uapi/asm-generic/ioctls.h
+++ b/include/uapi/asm-generic/ioctls.h
@@ -106,6 +106,9 @@
 # define FIOQSIZE	0x5460
 #endif
 
+#define TIOCSADDR	_IOWR('T', 0x63, struct serial_addr)
+#define TIOCGADDR	_IOWR('T', 0x64, struct serial_addr)
+
 /* Used for packet mode */
 #define TIOCPKT_DATA		 0
 #define TIOCPKT_FLUSHREAD	 1
diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
index f868685b35a0..7b198fd5d390 100644
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -151,4 +151,12 @@ struct serial_iso7816 {
 	__u32	reserved[5];
 };
 
+struct serial_addr {
+	__u32	flags;
+#define SER_ADDR_RECV			(1 << 0)
+#define SER_ADDR_RECV_CLEAR		(1 << 1)
+#define SER_ADDR_DEST			(1 << 2)
+	__u32	addr;
+};
+
 #endif /* _UAPI_LINUX_SERIAL_H */
-- 
2.30.2

Re: [RFC PATCH 6/7] serial: General support for multipoint addresses

[Lukas Wunner]

On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> This patch adds generic support for serial multipoint
> addressing. Two new ioctls are added. TIOCSADDR is used to

Nit:  "This patch adds..." is superfluous.  Just write "Add ..."
in imperative mood.


> This change is necessary for supporting devices with RS485
> multipoint addressing [*].

If this is only used with RS485, why can't we just store the
addresses in struct serial_rs485 and use the existing TIOCSRS485
and TIOCGRS485 ioctls?  There's 20 bytes of padding left in
struct serial_rs485 which you could use.  No need to add more
user-space ABI.


> [*] Technically, RS485 is just an electronic spec and does not
> itself specify the 9th bit addressing mode but 9th bit seems
> at least "semi-standard" way to do addressing with RS485.

Is 9th bit addressing actually used by an Intel customer or was
it implemented just for feature completeness?  I think this mode
isn't used often (I've never seen a use case myself), primarily
because it requires disabling parity.

Thanks,

Lukas

Re: [RFC PATCH 6/7] serial: General support for multipoint addresses

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1383 bytes --]

On Sun, 6 Mar 2022, Lukas Wunner wrote:

> On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> 
> > This change is necessary for supporting devices with RS485
> > multipoint addressing [*].
> 
> If this is only used with RS485, why can't we just store the
> addresses in struct serial_rs485 and use the existing TIOCSRS485
> and TIOCGRS485 ioctls?  There's 20 bytes of padding left in
> struct serial_rs485 which you could use.  No need to add more
> user-space ABI.

It could if it is agreed that serial multipoint addressing is just
a thing in RS-485 and nowhere else? In that case, there is no point
in adding more generic support for it.

> > [*] Technically, RS485 is just an electronic spec and does not
> > itself specify the 9th bit addressing mode but 9th bit seems
> > at least "semi-standard" way to do addressing with RS485.
> 
> Is 9th bit addressing actually used by an Intel customer or was
> it implemented just for feature completeness? I think this mode
> isn't used often (I've never seen a use case myself), primarily
> because it requires disabling parity.

On what basis? ...The datasheet I'm looking at has a timing diagram 
with both D8 (9th bit) and parity so I think your information must be
incorrect. I don't have direct contacts with customers but I'm told
it's important for other org's customers.


-- 
 i.

Re: [RFC PATCH 6/7] serial: General support for multipoint addresses

[Lukas Wunner]

On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote:
> On Sun, 6 Mar 2022, Lukas Wunner wrote:
> > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> > > This change is necessary for supporting devices with RS485
> > > multipoint addressing [*].
> > 
> > If this is only used with RS485, why can't we just store the
> > addresses in struct serial_rs485 and use the existing TIOCSRS485
> > and TIOCGRS485 ioctls?  There's 20 bytes of padding left in
> > struct serial_rs485 which you could use.  No need to add more
> > user-space ABI.
> 
> It could if it is agreed that serial multipoint addressing is just
> a thing in RS-485 and nowhere else? In that case, there is no point
> in adding more generic support for it.

It's just that the above-quoted sentence in the commit message
specifically mentions RS485.  If you intend to use it with RS232
as well, that should be made explicit, otherwise one wonders why
it wasn't integrated into struct serial_rs485.

I have no idea how common 9th bit addressing mode is with RS232.
Goggle turns up links saying it's mainly used with RS485, "but also
RS232".  Since RS232 isn't a bus but a point-to-point link,
9th bit addressing doesn't seem to make as much sense.


> > > [*] Technically, RS485 is just an electronic spec and does not
> > > itself specify the 9th bit addressing mode but 9th bit seems
> > > at least "semi-standard" way to do addressing with RS485.
> > 
> > Is 9th bit addressing actually used by an Intel customer or was
> > it implemented just for feature completeness? I think this mode
> > isn't used often (I've never seen a use case myself), primarily
> > because it requires disabling parity.
> 
> On what basis? ...The datasheet I'm looking at has a timing diagram 
> with both D8 (9th bit) and parity so I think your information must be
> incorrect.

E.g. the discussion here says that 9th bit addressing requires that
parity is disabled or the character size is reduced to 7-bit:

https://www.microchip.com/forums/m299904.aspx

I guess that applies only to some UARTs, the Synopsys databook doesn't
mention any such constraints.

Thanks,

Lukas

Re: [RFC PATCH 6/7] serial: General support for multipoint addresses

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1760 bytes --]

On Wed, 9 Mar 2022, Lukas Wunner wrote:

> On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote:
> > On Sun, 6 Mar 2022, Lukas Wunner wrote:
> > > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> > > > This change is necessary for supporting devices with RS485
> > > > multipoint addressing [*].
> > > 
> > > If this is only used with RS485, why can't we just store the
> > > addresses in struct serial_rs485 and use the existing TIOCSRS485
> > > and TIOCGRS485 ioctls?  There's 20 bytes of padding left in
> > > struct serial_rs485 which you could use.  No need to add more
> > > user-space ABI.
> > 
> > It could if it is agreed that serial multipoint addressing is just
> > a thing in RS-485 and nowhere else? In that case, there is no point
> > in adding more generic support for it.
> 
> It's just that the above-quoted sentence in the commit message
> specifically mentions RS485.

That sentence is just to justify why addressing mode is needed,
not to take a stance on whether it is only used with RS485 or not.

> If you intend to use it with RS232
> as well, that should be made explicit, otherwise one wonders why
> it wasn't integrated into struct serial_rs485.
> 
> I have no idea how common 9th bit addressing mode is with RS232.
> Goggle turns up links saying it's mainly used with RS485, "but also
> RS232".  Since RS232 isn't a bus but a point-to-point link,
> 9th bit addressing doesn't seem to make as much sense.

While I don't know any better, I can image though that with an 
RS232-to-RS485 converter, it could make some sense.

If I put them back to serial_rs485 / rs485 config, it's basically just 
where I initially started from with this patchset (offlist).


-- 
 i.

Re: [RFC PATCH 6/7] serial: General support for multipoint addresses

[Andy Shevchenko]

On Wed, Mar 09, 2022 at 08:05:21PM +0100, Lukas Wunner wrote:
> On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote:
> > On Sun, 6 Mar 2022, Lukas Wunner wrote:
> > > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> > > > This change is necessary for supporting devices with RS485
> > > > multipoint addressing [*].
> > > 
> > > If this is only used with RS485, why can't we just store the
> > > addresses in struct serial_rs485 and use the existing TIOCSRS485
> > > and TIOCGRS485 ioctls?  There's 20 bytes of padding left in
> > > struct serial_rs485 which you could use.  No need to add more
> > > user-space ABI.
> > 
> > It could if it is agreed that serial multipoint addressing is just
> > a thing in RS-485 and nowhere else? In that case, there is no point
> > in adding more generic support for it.
> 
> It's just that the above-quoted sentence in the commit message
> specifically mentions RS485.  If you intend to use it with RS232
> as well, that should be made explicit, otherwise one wonders why
> it wasn't integrated into struct serial_rs485.
> 
> I have no idea how common 9th bit addressing mode is with RS232.
> Goggle turns up links saying it's mainly used with RS485, "but also
> RS232".  Since RS232 isn't a bus but a point-to-point link,
> 9th bit addressing doesn't seem to make as much sense.

In my student years I have an exercise to use 9-bit addressing mode on RS232.
Obviously I forgot all of the details, but I remember that that has a practical
application.

-- 
With Best Regards,
Andy Shevchenko