[PATCH v5 00/10] Add RS485 support to DW UART

[PATCH v5 00/10] Add RS485 support to DW UART

[Ilpo Järvinen]

This patchset adds RS-485 support to the DW UART driver. The patchset
has two main parts. The first part adds HW support for RS-485 itself
in various modes of operation and the second part focuses on enabling
9th bit addressing mode that can be used on a multipoint RS-485
communications line.

To configure multipoint addressing, ADDRB flag is added to termios
and two new IOCTLs are added into serial core. Lukas Wunner brought up
during v1 review that if this addressing is only going to be used with
RS-485, doing it within rs485_config would avoid having to add those
IOCTLs. There was some counterexample w/o further details mentioned for
RS-232 usage by Andy Shevchenko. I left the IOCTL approach there but if
somebody has further input on this, please voice it as it is user-space
facing API.

I decided to rewrite the UART_CAP_NOTEMT patch from scratch myself
based on Uwe Kleine-König's earlier suggestion and include it to this
series. To make waiting for a single character easy and to avoid
storing it per purpose in the uart drivers, I decided to add
frame_time into uart_port. It turned out to beneficial also for serial
core which had to reverse calculate it from uart_port->timeout). I was
thinking of removing uart_port->timeout entirely and derive the value
timeout from frame_time and fifosize where needed but I was not sure
if that's ok to do lockingwise (not that fifosize is a variable that
is expected to change so maybe I'm just being too cautious).

Cc: linux-api@vger.kernel.org

v1 -> v2:
- Add uart_port->frame_time to avoid the need to store it per purpose
- Included NOTEMT patch rewritten from scratch
- Merge HW half & full-duplex patches
- Detect RS485 HW using RE_EN register write+read
- Removed SER_RS485_SW_RX_OR_TX
- Relocated/renamed RE polarity DT prop
- Use SER_RS485_RTS_ON_SEND rather than DT prop directly
- Removed DE polarity prop, it is still configurable but with rts one instead
- Make DE active-high by default in dwlib
- Don't unnecessarily clear DE/RE_EN for non-RS485 mode
- Prevent ADDRB and addrmode desync for RS485->RS232 transition
- Added ACPI enumeration doc
- Changed -EINVAL to -ENOTTY if no set/get_addr handler is present
- Clear ADDRB in set_termios of a few more drivers
- Added filtering for addresses to avoid them leaking into data stream
- Reworded comments & commit messages as requested

v2 -> v3:
- Change ADDRB to 0x20000000 which is free for all archs
- Added TIOCSADDR/GADDR to tty_compat_ioctl

v3 -> v4:
- defined DW_UART_ADDR_MASK instead of 0xff
- Adapt to UART_CAP_NOTEMT that already exists (is currently no-op)
- Corrected delay_rts_after_send conversion to nsec
- Make 8250 DMA code to use THRE & __stop_tx
- Add roughly one extra bit to stop_delay to prevent too early RTS deassert

v4 -> v5:
- rebased series to tty-testing

Ilpo Järvinen (10):
  serial: 8250_dwlib: RS485 HW half & full duplex support
  serial: 8250_dwlib: Implement SW half duplex support
  dt_bindings: rs485: Add receiver enable polarity
  ACPI / property: Document RS485 _DSD properties
  serial: termbits: ADDRB to indicate 9th bit addressing mode
  serial: General support for multipoint addresses
  serial: 8250: make saved LSR larger
  serial: 8250: create lsr_save_mask
  serial: 8250_lpss: Use 32-bit reads
  serial: 8250_dwlib: Support for 9th bit multipoint addressing

 .../devicetree/bindings/serial/rs485.yaml     |   5 +
 .../driver-api/serial/serial-rs485.rst        |  23 +-
 .../firmware-guide/acpi/enumeration.rst       |  25 ++
 arch/alpha/include/uapi/asm/ioctls.h          |   3 +
 arch/alpha/include/uapi/asm/termbits.h        |   1 +
 arch/mips/include/uapi/asm/ioctls.h           |   3 +
 arch/mips/include/uapi/asm/termbits.h         |   1 +
 arch/parisc/include/uapi/asm/ioctls.h         |   3 +
 arch/parisc/include/uapi/asm/termbits.h       |   1 +
 arch/powerpc/include/uapi/asm/ioctls.h        |   3 +
 arch/powerpc/include/uapi/asm/termbits.h      |   1 +
 arch/sh/include/uapi/asm/ioctls.h             |   3 +
 arch/sparc/include/uapi/asm/ioctls.h          |   3 +
 arch/sparc/include/uapi/asm/termbits.h        |   1 +
 arch/xtensa/include/uapi/asm/ioctls.h         |   3 +
 drivers/char/pcmcia/synclink_cs.c             |   2 +
 drivers/ipack/devices/ipoctal.c               |   2 +
 drivers/mmc/core/sdio_uart.c                  |   2 +
 drivers/net/usb/hso.c                         |   3 +-
 drivers/s390/char/tty3270.c                   |   3 +
 drivers/staging/greybus/uart.c                |   2 +
 drivers/tty/amiserial.c                       |   6 +-
 drivers/tty/moxa.c                            |   1 +
 drivers/tty/mxser.c                           |   1 +
 drivers/tty/serial/8250/8250_core.c           |   6 +-
 drivers/tty/serial/8250/8250_dwlib.c          | 232 +++++++++++++++++-
 drivers/tty/serial/8250/8250_dwlib.h          |   5 +
 drivers/tty/serial/8250/8250_lpss.c           |   2 +-
 drivers/tty/serial/8250/8250_port.c           |  14 +-
 drivers/tty/serial/serial_core.c              |  62 +++++
 drivers/tty/synclink_gt.c                     |   2 +
 drivers/tty/tty_io.c                          |   2 +
 drivers/tty/tty_ioctl.c                       |   2 +
 drivers/usb/class/cdc-acm.c                   |   2 +
 drivers/usb/serial/usb-serial.c               |   6 +-
 include/linux/serial_8250.h                   |   7 +-
 include/linux/serial_core.h                   |   6 +
 include/uapi/asm-generic/ioctls.h             |   3 +
 include/uapi/asm-generic/termbits.h           |   1 +
 include/uapi/linux/serial.h                   |   8 +
 net/bluetooth/rfcomm/tty.c                    |   2 +
 41 files changed, 445 insertions(+), 18 deletions(-)

-- 
2.30.2

[PATCH v5 05/10] 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: 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/char/pcmcia/synclink_cs.c        | 2 ++
 drivers/ipack/devices/ipoctal.c          | 2 ++
 drivers/mmc/core/sdio_uart.c             | 2 ++
 drivers/net/usb/hso.c                    | 3 ++-
 drivers/s390/char/tty3270.c              | 3 +++
 drivers/staging/greybus/uart.c           | 2 ++
 drivers/tty/amiserial.c                  | 6 +++++-
 drivers/tty/moxa.c                       | 1 +
 drivers/tty/mxser.c                      | 1 +
 drivers/tty/serial/serial_core.c         | 2 ++
 drivers/tty/synclink_gt.c                | 2 ++
 drivers/tty/tty_ioctl.c                  | 2 ++
 drivers/usb/class/cdc-acm.c              | 2 ++
 drivers/usb/serial/usb-serial.c          | 6 ++++--
 include/uapi/asm-generic/termbits.h      | 1 +
 net/bluetooth/rfcomm/tty.c               | 2 ++
 21 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/termbits.h b/arch/alpha/include/uapi/asm/termbits.h
index 4575ba34a0ea..0c123e715486 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	004000000000		/* 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..4732d31b0e4e 100644
--- a/arch/mips/include/uapi/asm/termbits.h
+++ b/arch/mips/include/uapi/asm/termbits.h
@@ -182,6 +182,7 @@ struct ktermios {
 #define	 B3500000 0010016
 #define	 B4000000 0010017
 #define CIBAUD	  002003600000	/* input baud rate */
+#define ADDRB	  004000000000	/* address bit */
 #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..d6bbd10d92ba 100644
--- a/arch/parisc/include/uapi/asm/termbits.h
+++ b/arch/parisc/include/uapi/asm/termbits.h
@@ -159,6 +159,7 @@ struct ktermios {
 #define  B3500000 0010016
 #define  B4000000 0010017
 #define CIBAUD    002003600000		/* input baud rate */
+#define ADDRB	  004000000000		/* address bit */
 #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..c6a033732f39 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	004000000000		/* 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..5eb1d547b5c4 100644
--- a/arch/sparc/include/uapi/asm/termbits.h
+++ b/arch/sparc/include/uapi/asm/termbits.h
@@ -201,6 +201,7 @@ struct ktermios {
 #define B3500000  0x00001012
 #define B4000000  0x00001013  */
 #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
+#define ADDRB	  0x20000000  /* address bit */
 #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
 #define CRTSCTS	  0x80000000  /* flow control */
 
diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 78baba55a8b5..d179b9b57a25 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -2287,6 +2287,8 @@ static void mgslpc_set_termios(struct tty_struct *tty, struct ktermios *old_term
 		== RELEVANT_IFLAG(old_termios->c_iflag)))
 	  return;
 
+	tty->termios.c_cflag &= ~ADDRB;
+
 	mgslpc_change_params(info, tty);
 
 	/* Handle transition to B0 status */
diff --git a/drivers/ipack/devices/ipoctal.c b/drivers/ipack/devices/ipoctal.c
index 20d2b9ec1227..d66cc9683ebc 100644
--- a/drivers/ipack/devices/ipoctal.c
+++ b/drivers/ipack/devices/ipoctal.c
@@ -506,6 +506,8 @@ static void ipoctal_set_termios(struct tty_struct *tty,
 	struct ipoctal_channel *channel = tty->driver_data;
 	speed_t baud;
 
+	tty->termios.c_cflag &= ~ADDRB;
+
 	cflag = tty->termios.c_cflag;
 
 	/* Disable and reset everything before change the setup */
diff --git a/drivers/mmc/core/sdio_uart.c b/drivers/mmc/core/sdio_uart.c
index 414aa82abc39..f28075952f3e 100644
--- a/drivers/mmc/core/sdio_uart.c
+++ b/drivers/mmc/core/sdio_uart.c
@@ -867,6 +867,8 @@ static void sdio_uart_set_termios(struct tty_struct *tty,
 	if (sdio_uart_claim_func(port) != 0)
 		return;
 
+	tty->termios.c_cflag &= ~ADDRB;
+
 	sdio_uart_change_speed(port, &tty->termios, old_termios);
 
 	/* Handle transition to B0 status */
diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index f8221a7acf62..056352618804 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1099,7 +1099,8 @@ static void _hso_serial_set_termios(struct tty_struct *tty)
 		~(CSIZE		/* no size */
 		| PARENB	/* disable parity bit */
 		| CBAUD		/* clear current baud rate */
-		| CBAUDEX);	/* clear current buad rate */
+		| CBAUDEX	/* clear current baud rate */
+		| ADDRB);	/* disable 9th (addr) bit */
 
 	tty->termios.c_cflag |= CS8;	/* character size 8 bits */
 
diff --git a/drivers/s390/char/tty3270.c b/drivers/s390/char/tty3270.c
index 5c83f71c1d0e..253d2997a1d3 100644
--- a/drivers/s390/char/tty3270.c
+++ b/drivers/s390/char/tty3270.c
@@ -1768,6 +1768,9 @@ tty3270_set_termios(struct tty_struct *tty, struct ktermios *old)
 	tp = tty->driver_data;
 	if (!tp)
 		return;
+
+	tty->termios.c_cflag &= ~ADDRB;
+
 	spin_lock_bh(&tp->view.lock);
 	if (L_ICANON(tty)) {
 		new = L_ECHO(tty) ? TF_INPUT: TF_INPUTN;
diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index dc4ed0ff1ae2..83e73aefde0f 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -487,6 +487,8 @@ static void gb_tty_set_termios(struct tty_struct *tty,
 	struct ktermios *termios = &tty->termios;
 	u8 newctrl = gb_tty->ctrlout;
 
+	termios->c_cflag &= ~ADDRB;
+
 	newline.rate = cpu_to_le32(tty_get_baud_rate(tty));
 	newline.format = termios->c_cflag & CSTOPB ?
 				GB_SERIAL_2_STOP_BITS : GB_SERIAL_1_STOP_BITS;
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 6ebd3e4ed859..79c542aca1c3 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 82a1770dd808..0f397e67eeb0 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1540,6 +1540,8 @@ 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/synclink_gt.c b/drivers/tty/synclink_gt.c
index 9bc2a9265277..180f38f0f57a 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -714,6 +714,8 @@ static void set_termios(struct tty_struct *tty, struct ktermios *old_termios)
 
 	DBGINFO(("%s set_termios\n", tty->driver->name));
 
+	tty->termios.c_cflag &= ~ADDRB;
+
 	change_params(info);
 
 	/* Handle transition to B0 status */
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/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 9b9aea24d58c..fd246ec70da8 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1056,6 +1056,8 @@ static void acm_tty_set_termios(struct tty_struct *tty,
 	struct usb_cdc_line_coding newline;
 	int newctrl = acm->ctrlout;
 
+	termios->c_cflag &= ~ADDRB;
+
 	newline.dwDTERate = cpu_to_le32(tty_get_baud_rate(tty));
 	newline.bCharFormat = termios->c_cflag & CSTOPB ? 2 : 0;
 	newline.bParityType = termios->c_cflag & PARENB ?
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 24101bd7fcad..8d1d170eb7e6 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -525,10 +525,12 @@ 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);
+	}
 }
 
 static int serial_break(struct tty_struct *tty, int break_state)
diff --git a/include/uapi/asm-generic/termbits.h b/include/uapi/asm-generic/termbits.h
index 2fbaf9ae89dd..e06eaa9cf8be 100644
--- a/include/uapi/asm-generic/termbits.h
+++ b/include/uapi/asm-generic/termbits.h
@@ -158,6 +158,7 @@ struct ktermios {
 #define  B3500000 0010016
 #define  B4000000 0010017
 #define CIBAUD	  002003600000	/* input baud rate */
+#define ADDRB	  004000000000	/* address bit */
 #define CMSPAR	  010000000000	/* mark or space (stick) parity */
 #define CRTSCTS	  020000000000	/* flow control */
 
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index ebd78fdbd6e8..832e725f23ab 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -871,6 +871,8 @@ static void rfcomm_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 	if (!dev || !dev->dlc || !dev->dlc->session)
 		return;
 
+	new->c_cflag &= ~ADDRB;
+
 	/* Handle turning off CRTSCTS */
 	if ((old->c_cflag & CRTSCTS) && !(new->c_cflag & CRTSCTS))
 		BT_DBG("Turning off CRTSCTS unsupported");
-- 
2.30.2

[PATCH v5 06/10] serial: General support for multipoint addresses

[Ilpo Järvinen]

Add 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@vger.kernel.org
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: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-xtensa@linux-xtensa.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 .../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 ++++++++++++++++++-
 drivers/tty/tty_io.c                          |  2 +
 include/linux/serial_core.h                   |  6 ++
 include/uapi/asm-generic/ioctls.h             |  3 +
 include/uapi/linux/serial.h                   |  8 +++
 14 files changed, 125 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 0f397e67eeb0..5762987bf176 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1397,6 +1397,56 @@ 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 (!port->set_addr)
+		return -ENOTTY;
+
+	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
+		return -EFAULT;
+
+	spin_lock_irqsave(&port->lock, flags);
+	ret = port->set_addr(port, &addr);
+	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 (!port->get_addr)
+		return -ENOTTY;
+
+	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
+		return -EFAULT;
+
+	spin_lock_irqsave(&port->lock, flags);
+	ret = port->get_addr(port, &addr);
+	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.
  */
@@ -1474,6 +1524,15 @@ 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);
@@ -1540,7 +1599,8 @@ 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/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 8fec1d8648f5..ef22b95e9c79 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2885,6 +2885,8 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
 	case TIOCSERGETLSR:
 	case TIOCGRS485:
 	case TIOCSRS485:
+	case TIOCSADDR:
+	case TIOCGADDR:
 #ifdef TIOCGETP
 	case TIOCGETP:
 	case TIOCSETP:
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cbd5070bc87f..2dd4c4d01c59 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 fa6b16e5fdd8..8cb785ea7087 100644
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -149,4 +149,12 @@ 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: [PATCH v5 00/10] Add RS485 support to DW UART

[Greg KH]

On Tue, Apr 26, 2022 at 03:24:38PM +0300, Ilpo Järvinen wrote:
> This patchset adds RS-485 support to the DW UART driver. The patchset
> has two main parts. The first part adds HW support for RS-485 itself
> in various modes of operation and the second part focuses on enabling
> 9th bit addressing mode that can be used on a multipoint RS-485
> communications line.
> 
> To configure multipoint addressing, ADDRB flag is added to termios
> and two new IOCTLs are added into serial core. Lukas Wunner brought up
> during v1 review that if this addressing is only going to be used with
> RS-485, doing it within rs485_config would avoid having to add those
> IOCTLs. There was some counterexample w/o further details mentioned for
> RS-232 usage by Andy Shevchenko. I left the IOCTL approach there but if
> somebody has further input on this, please voice it as it is user-space
> facing API.
> 
> I decided to rewrite the UART_CAP_NOTEMT patch from scratch myself
> based on Uwe Kleine-König's earlier suggestion and include it to this
> series. To make waiting for a single character easy and to avoid
> storing it per purpose in the uart drivers, I decided to add
> frame_time into uart_port. It turned out to beneficial also for serial
> core which had to reverse calculate it from uart_port->timeout). I was
> thinking of removing uart_port->timeout entirely and derive the value
> timeout from frame_time and fifosize where needed but I was not sure
> if that's ok to do lockingwise (not that fifosize is a variable that
> is expected to change so maybe I'm just being too cautious).

I've applied the first 4 now, thanks.

greg k-h

Re: [PATCH v5 05/10] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Greg KH]

On Tue, Apr 26, 2022 at 03:24:43PM +0300, Ilpo Järvinen wrote:
> 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: 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/char/pcmcia/synclink_cs.c        | 2 ++
>  drivers/ipack/devices/ipoctal.c          | 2 ++
>  drivers/mmc/core/sdio_uart.c             | 2 ++
>  drivers/net/usb/hso.c                    | 3 ++-
>  drivers/s390/char/tty3270.c              | 3 +++
>  drivers/staging/greybus/uart.c           | 2 ++
>  drivers/tty/amiserial.c                  | 6 +++++-
>  drivers/tty/moxa.c                       | 1 +
>  drivers/tty/mxser.c                      | 1 +
>  drivers/tty/serial/serial_core.c         | 2 ++
>  drivers/tty/synclink_gt.c                | 2 ++
>  drivers/tty/tty_ioctl.c                  | 2 ++
>  drivers/usb/class/cdc-acm.c              | 2 ++
>  drivers/usb/serial/usb-serial.c          | 6 ++++--
>  include/uapi/asm-generic/termbits.h      | 1 +
>  net/bluetooth/rfcomm/tty.c               | 2 ++
>  21 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/alpha/include/uapi/asm/termbits.h b/arch/alpha/include/uapi/asm/termbits.h
> index 4575ba34a0ea..0c123e715486 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	004000000000		/* 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..4732d31b0e4e 100644
> --- a/arch/mips/include/uapi/asm/termbits.h
> +++ b/arch/mips/include/uapi/asm/termbits.h
> @@ -182,6 +182,7 @@ struct ktermios {
>  #define	 B3500000 0010016
>  #define	 B4000000 0010017
>  #define CIBAUD	  002003600000	/* input baud rate */
> +#define ADDRB	  004000000000	/* address bit */
>  #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..d6bbd10d92ba 100644
> --- a/arch/parisc/include/uapi/asm/termbits.h
> +++ b/arch/parisc/include/uapi/asm/termbits.h
> @@ -159,6 +159,7 @@ struct ktermios {
>  #define  B3500000 0010016
>  #define  B4000000 0010017
>  #define CIBAUD    002003600000		/* input baud rate */
> +#define ADDRB	  004000000000		/* address bit */

tabs where the rest were not?

>  #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..c6a033732f39 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	004000000000		/* 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..5eb1d547b5c4 100644
> --- a/arch/sparc/include/uapi/asm/termbits.h
> +++ b/arch/sparc/include/uapi/asm/termbits.h
> @@ -201,6 +201,7 @@ struct ktermios {
>  #define B3500000  0x00001012
>  #define B4000000  0x00001013  */
>  #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
> +#define ADDRB	  0x20000000  /* address bit */
>  #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
>  #define CRTSCTS	  0x80000000  /* flow control */

Why all the different values?  Can't we pick one and use it for all
arches?  Having these be different in different arches and userspace
should not be a thing for new fields, right?

> diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
> index 78baba55a8b5..d179b9b57a25 100644
> --- a/drivers/char/pcmcia/synclink_cs.c
> +++ b/drivers/char/pcmcia/synclink_cs.c
> @@ -2287,6 +2287,8 @@ static void mgslpc_set_termios(struct tty_struct *tty, struct ktermios *old_term
>  		== RELEVANT_IFLAG(old_termios->c_iflag)))
>  	  return;
>  
> +	tty->termios.c_cflag &= ~ADDRB;

Having to do this for all drivers feels wrong.  It isn't needed for any
other flag, right?  That makes me really not like this change as it
feels very ackward and
yet-another-thing-a-serial-driver-has-to-remember.

And as you are wanting to pass this bit to userspace, where is that
documented?

thanks,

greg k-h

Re: [PATCH v5 06/10] serial: General support for multipoint addresses

[Greg KH]

On Tue, Apr 26, 2022 at 03:24:44PM +0300, Ilpo Järvinen wrote:
> Add 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@vger.kernel.org
> 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: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: linux-sh@vger.kernel.org
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: sparclinux@vger.kernel.org
> Cc: Chris Zankel <chris@zankel.net>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Cc: linux-xtensa@linux-xtensa.org
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> ---
>  .../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 ++++++++++++++++++-
>  drivers/tty/tty_io.c                          |  2 +
>  include/linux/serial_core.h                   |  6 ++
>  include/uapi/asm-generic/ioctls.h             |  3 +
>  include/uapi/linux/serial.h                   |  8 +++
>  14 files changed, 125 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 0f397e67eeb0..5762987bf176 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1397,6 +1397,56 @@ 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 (!port->set_addr)
> +		return -ENOTTY;
> +
> +	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
> +		return -EFAULT;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	ret = port->set_addr(port, &addr);
> +	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 (!port->get_addr)
> +		return -ENOTTY;
> +
> +	if (copy_from_user(&addr, serial_addr_user, sizeof(*serial_addr_user)))
> +		return -EFAULT;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	ret = port->get_addr(port, &addr);
> +	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.
>   */
> @@ -1474,6 +1524,15 @@ 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);
> @@ -1540,7 +1599,8 @@ 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/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 8fec1d8648f5..ef22b95e9c79 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2885,6 +2885,8 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
>  	case TIOCSERGETLSR:
>  	case TIOCGRS485:
>  	case TIOCSRS485:
> +	case TIOCSADDR:
> +	case TIOCGADDR:
>  #ifdef TIOCGETP
>  	case TIOCGETP:
>  	case TIOCSETP:
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index cbd5070bc87f..2dd4c4d01c59 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 fa6b16e5fdd8..8cb785ea7087 100644
> --- a/include/uapi/linux/serial.h
> +++ b/include/uapi/linux/serial.h
> @@ -149,4 +149,12 @@ 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)

You never check for invalid flags being sent to the kernel, which means
this api can never change in the future to add new flags :(

And what about struct serial_rs485?  Shouldn't that be used here
instead?  Why do we need a new ioctl and structure?

thanks,

greg k-h

Re: [PATCH v5 05/10] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 7351 bytes --]

On Tue, 26 Apr 2022, Greg KH wrote:

> On Tue, Apr 26, 2022 at 03:24:43PM +0300, Ilpo Järvinen wrote:
> > 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: 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/char/pcmcia/synclink_cs.c        | 2 ++
> >  drivers/ipack/devices/ipoctal.c          | 2 ++
> >  drivers/mmc/core/sdio_uart.c             | 2 ++
> >  drivers/net/usb/hso.c                    | 3 ++-
> >  drivers/s390/char/tty3270.c              | 3 +++
> >  drivers/staging/greybus/uart.c           | 2 ++
> >  drivers/tty/amiserial.c                  | 6 +++++-
> >  drivers/tty/moxa.c                       | 1 +
> >  drivers/tty/mxser.c                      | 1 +
> >  drivers/tty/serial/serial_core.c         | 2 ++
> >  drivers/tty/synclink_gt.c                | 2 ++
> >  drivers/tty/tty_ioctl.c                  | 2 ++
> >  drivers/usb/class/cdc-acm.c              | 2 ++
> >  drivers/usb/serial/usb-serial.c          | 6 ++++--
> >  include/uapi/asm-generic/termbits.h      | 1 +
> >  net/bluetooth/rfcomm/tty.c               | 2 ++
> >  21 files changed, 40 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/alpha/include/uapi/asm/termbits.h b/arch/alpha/include/uapi/asm/termbits.h
> > index 4575ba34a0ea..0c123e715486 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	004000000000		/* 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..4732d31b0e4e 100644
> > --- a/arch/mips/include/uapi/asm/termbits.h
> > +++ b/arch/mips/include/uapi/asm/termbits.h
> > @@ -182,6 +182,7 @@ struct ktermios {
> >  #define	 B3500000 0010016
> >  #define	 B4000000 0010017
> >  #define CIBAUD	  002003600000	/* input baud rate */
> > +#define ADDRB	  004000000000	/* address bit */
> >  #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..d6bbd10d92ba 100644
> > --- a/arch/parisc/include/uapi/asm/termbits.h
> > +++ b/arch/parisc/include/uapi/asm/termbits.h
> > @@ -159,6 +159,7 @@ struct ktermios {
> >  #define  B3500000 0010016
> >  #define  B4000000 0010017
> >  #define CIBAUD    002003600000		/* input baud rate */
> > +#define ADDRB	  004000000000		/* address bit */
> 
> tabs where the rest were not?
> 
> >  #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..c6a033732f39 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	004000000000		/* 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..5eb1d547b5c4 100644
> > --- a/arch/sparc/include/uapi/asm/termbits.h
> > +++ b/arch/sparc/include/uapi/asm/termbits.h
> > @@ -201,6 +201,7 @@ struct ktermios {
> >  #define B3500000  0x00001012
> >  #define B4000000  0x00001013  */
> >  #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
> > +#define ADDRB	  0x20000000  /* address bit */
> >  #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
> >  #define CRTSCTS	  0x80000000  /* flow control */
> 
> Why all the different values?  Can't we pick one and use it for all
> arches?  Having these be different in different arches and userspace
> should not be a thing for new fields, right?
> 
> > diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
> > index 78baba55a8b5..d179b9b57a25 100644
> > --- a/drivers/char/pcmcia/synclink_cs.c
> > +++ b/drivers/char/pcmcia/synclink_cs.c
> > @@ -2287,6 +2287,8 @@ static void mgslpc_set_termios(struct tty_struct *tty, struct ktermios *old_term
> >  		== RELEVANT_IFLAG(old_termios->c_iflag)))
> >  	  return;
> >  
> > +	tty->termios.c_cflag &= ~ADDRB;
> 
> Having to do this for all drivers feels wrong.  It isn't needed for any
> other flag, right?

My understanding is that it would be needed for other flags too, it's just 
that many drivers probably haven't cared enough. Some drivers certainly 
clear a few flags they don't support while others don't clear any but
it's also challenging to determine it which flags which driver supports. 
How bad the impact is per flag varies.

> That makes me really not like this change as it
> feels very ackward and
> yet-another-thing-a-serial-driver-has-to-remember.

It would be nice to have some mask for supported bits per driver. But it
will be challenging to add at this point and I'm far from sure I could get 
them right per driver even if carefully trying to.

> And as you are wanting to pass this bit to userspace, where is that
> documented?

Ah, I probably should add it to driver-api/serial/driver.rst too but ADDRB
is certainly mentioned alongside with other addressing mode documentation
I wrote for the later changes in this series.

-- 
 i.

Re: [PATCH v5 06/10] serial: General support for multipoint addresses

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 4705 bytes --]

On Tue, 26 Apr 2022, Greg KH wrote:

> On Tue, Apr 26, 2022 at 03:24:44PM +0300, Ilpo Järvinen wrote:
> > Add 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@vger.kernel.org
> > 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: Yoshinori Sato <ysato@users.sourceforge.jp>
> > Cc: Rich Felker <dalias@libc.org>
> > Cc: linux-sh@vger.kernel.org
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: sparclinux@vger.kernel.org
> > Cc: Chris Zankel <chris@zankel.net>
> > Cc: Max Filippov <jcmvbkbc@gmail.com>
> > Cc: linux-xtensa@linux-xtensa.org
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: linux-arch@vger.kernel.org
> > Cc: linux-doc@vger.kernel.org
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > ---

> > diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
> > index fa6b16e5fdd8..8cb785ea7087 100644
> > --- a/include/uapi/linux/serial.h
> > +++ b/include/uapi/linux/serial.h
> > @@ -149,4 +149,12 @@ 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)
> 
> You never check for invalid flags being sent to the kernel, which means
> this api can never change in the future to add new flags :(

Ok, so you mean the general level should to check
if (...->flags & ~(SER_ADDR_FLAGS_ALL))
	return -EINVAL;
?

There's some code in the driver that detects invalid flag combinations 
(in 10/10) but I guess it doesn't satisfies what you're after. It is 
similar to how serial_rs485 flags is handled, that is, clearing flags it 
didn't handle (when it can) and returning -EINVAL for impossible 
combinations such as getting both RECV and DEST addr at the same time.
I don't know if serial_rs485 flags is a good example at all, it certainly 
doesn't check whether bits are set where there's no flag defined.

> And what about struct serial_rs485?  Shouldn't that be used here
> instead?  Why do we need a new ioctl and structure?

It is possible (Lukas already mentioned that option too). It just means
this will be available only on RS485 which could well be enough but Andy 
mentioned he has in the past come across addressing mode also with some 
RS232 thing (he didn't remember details anymore and it could be 
insignificant for the real world of today).


-- 
 i.

Re: [PATCH v5 06/10] serial: General support for multipoint addresses

[Greg KH]

On Tue, Apr 26, 2022 at 04:36:49PM +0300, Ilpo Järvinen wrote:
> On Tue, 26 Apr 2022, Greg KH wrote:
> 
> > On Tue, Apr 26, 2022 at 03:24:44PM +0300, Ilpo Järvinen wrote:
> > > Add 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@vger.kernel.org
> > > 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: Yoshinori Sato <ysato@users.sourceforge.jp>
> > > Cc: Rich Felker <dalias@libc.org>
> > > Cc: linux-sh@vger.kernel.org
> > > Cc: "David S. Miller" <davem@davemloft.net>
> > > Cc: sparclinux@vger.kernel.org
> > > Cc: Chris Zankel <chris@zankel.net>
> > > Cc: Max Filippov <jcmvbkbc@gmail.com>
> > > Cc: linux-xtensa@linux-xtensa.org
> > > Cc: Arnd Bergmann <arnd@arndb.de>
> > > Cc: linux-arch@vger.kernel.org
> > > Cc: linux-doc@vger.kernel.org
> > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > > ---
> 
> > > diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
> > > index fa6b16e5fdd8..8cb785ea7087 100644
> > > --- a/include/uapi/linux/serial.h
> > > +++ b/include/uapi/linux/serial.h
> > > @@ -149,4 +149,12 @@ 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)
> > 
> > You never check for invalid flags being sent to the kernel, which means
> > this api can never change in the future to add new flags :(
> 
> Ok, so you mean the general level should to check
> if (...->flags & ~(SER_ADDR_FLAGS_ALL))
> 	return -EINVAL;
> ?

For any new kernel api you always have to ensure that no "extra" flags
or bits are set and reject it otherwise you can never add any more bits
or flags in the future.  This should be in the Documentation/ directory
for how to add new ioctls somewhere.

> There's some code in the driver that detects invalid flag combinations 
> (in 10/10) but I guess it doesn't satisfies what you're after. It is 
> similar to how serial_rs485 flags is handled, that is, clearing flags it 
> didn't handle (when it can) and returning -EINVAL for impossible 
> combinations such as getting both RECV and DEST addr at the same time.
> I don't know if serial_rs485 flags is a good example at all, it certainly 
> doesn't check whether bits are set where there's no flag defined.
> 
> > And what about struct serial_rs485?  Shouldn't that be used here
> > instead?  Why do we need a new ioctl and structure?
> 
> It is possible (Lukas already mentioned that option too). It just means
> this will be available only on RS485 which could well be enough but Andy 
> mentioned he has in the past come across addressing mode also with some 
> RS232 thing (he didn't remember details anymore and it could be 
> insignificant for the real world of today).

This is rs485 so let's keep it attached to that.  Lots of people do
their own custom addressing schemes on top of 232 but that's up to them
to support in userspace or as a line discipline.

thanks,

greg k-h

Re: [PATCH v5 05/10] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 5122 bytes --]

One additional thing below I missed on the first read.

On Tue, 26 Apr 2022, Ilpo Järvinen wrote:
> On Tue, 26 Apr 2022, Greg KH wrote:
> 
> > On Tue, Apr 26, 2022 at 03:24:43PM +0300, Ilpo Järvinen wrote:
> > > 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: 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>
> > > ---

> > >  #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..c6a033732f39 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	004000000000		/* 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..5eb1d547b5c4 100644
> > > --- a/arch/sparc/include/uapi/asm/termbits.h
> > > +++ b/arch/sparc/include/uapi/asm/termbits.h
> > > @@ -201,6 +201,7 @@ struct ktermios {
> > >  #define B3500000  0x00001012
> > >  #define B4000000  0x00001013  */
> > >  #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
> > > +#define ADDRB	  0x20000000  /* address bit */
> > >  #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
> > >  #define CRTSCTS	  0x80000000  /* flow control */
> > 
> > Why all the different values?  Can't we pick one and use it for all
> > arches?  Having these be different in different arches and userspace
> > should not be a thing for new fields, right?

ADDRB value is the same for all archs (it's just this octal vs hex 
notation I've followed as per the nearby defines within the same file
which makes them look different).

Should I perhaps add to my cleanup list conversion of all those octal ones 
to hex?

> > > diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
> > > index 78baba55a8b5..d179b9b57a25 100644
> > > --- a/drivers/char/pcmcia/synclink_cs.c
> > > +++ b/drivers/char/pcmcia/synclink_cs.c
> > > @@ -2287,6 +2287,8 @@ static void mgslpc_set_termios(struct tty_struct *tty, struct ktermios *old_term
> > >  		== RELEVANT_IFLAG(old_termios->c_iflag)))
> > >  	  return;
> > >  
> > > +	tty->termios.c_cflag &= ~ADDRB;
> > 
> > Having to do this for all drivers feels wrong.  It isn't needed for any
> > other flag, right?
> 
> My understanding is that it would be needed for other flags too, it's just 
> that many drivers probably haven't cared enough. Some drivers certainly 
> clear a few flags they don't support while others don't clear any but
> it's also challenging to determine it which flags which driver supports. 
> How bad the impact is per flag varies.
> 
> > That makes me really not like this change as it
> > feels very ackward and
> > yet-another-thing-a-serial-driver-has-to-remember.
> 
> It would be nice to have some mask for supported bits per driver. But it
> will be challenging to add at this point and I'm far from sure I could get 
> them right per driver even if carefully trying to.
> 
> > And as you are wanting to pass this bit to userspace, where is that
> > documented?
> 
> Ah, I probably should add it to driver-api/serial/driver.rst too but ADDRB
> is certainly mentioned alongside with other addressing mode documentation
> I wrote for the later changes in this series.

-- 
 i.

Re: [PATCH v5 05/10] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Greg KH]

On Tue, Apr 26, 2022 at 05:01:31PM +0300, Ilpo Järvinen wrote:
> One additional thing below I missed on the first read.
> 
> On Tue, 26 Apr 2022, Ilpo Järvinen wrote:
> > On Tue, 26 Apr 2022, Greg KH wrote:
> > 
> > > On Tue, Apr 26, 2022 at 03:24:43PM +0300, Ilpo Järvinen wrote:
> > > > 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: 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>
> > > > ---
> 
> > > >  #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..c6a033732f39 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	004000000000		/* 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..5eb1d547b5c4 100644
> > > > --- a/arch/sparc/include/uapi/asm/termbits.h
> > > > +++ b/arch/sparc/include/uapi/asm/termbits.h
> > > > @@ -201,6 +201,7 @@ struct ktermios {
> > > >  #define B3500000  0x00001012
> > > >  #define B4000000  0x00001013  */
> > > >  #define CIBAUD	  0x100f0000  /* input baud rate (not used) */
> > > > +#define ADDRB	  0x20000000  /* address bit */
> > > >  #define CMSPAR	  0x40000000  /* mark or space (stick) parity */
> > > >  #define CRTSCTS	  0x80000000  /* flow control */
> > > 
> > > Why all the different values?  Can't we pick one and use it for all
> > > arches?  Having these be different in different arches and userspace
> > > should not be a thing for new fields, right?
> 
> ADDRB value is the same for all archs (it's just this octal vs hex 
> notation I've followed as per the nearby defines within the same file
> which makes them look different).
> 
> Should I perhaps add to my cleanup list conversion of all those octal ones 
> to hex?

Argh, yes, please, let's do that now, I totally missed that.  Will let
us see how to unify them as well.

thanks,

greg k-h

Re: [PATCH v5 05/10] serial: termbits: ADDRB to indicate 9th bit addressing mode

[Ilpo Järvinen]

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On Tue, 26 Apr 2022, Greg KH wrote:

> On Tue, Apr 26, 2022 at 05:01:31PM +0300, Ilpo Järvinen wrote:
> > 
> > ADDRB value is the same for all archs (it's just this octal vs hex 
> > notation I've followed as per the nearby defines within the same file
> > which makes them look different).
> > 
> > Should I perhaps add to my cleanup list conversion of all those octal ones 
> > to hex?
> 
> Argh, yes, please, let's do that now, I totally missed that.  Will let
> us see how to unify them as well.

Unifying them might turn out impractical, here's a rough idea now many
copies ... | uniq -c finds for the defines (based on more aggressively 
cleaned up lines than the patch will have):
     89 1
     74 2
     14 3
     58 4
     11 5
     54 6
There just tends to be 1 or 2 archs which are different from the others.

...I'll send the actual octal-to-hex patch once the arch builds complete.

-- 
 i.