Re: [PATCH v3 6/6] tty: serial: 8250: Add support for MOXA PCIe boards to switch interface between RS422/RS485

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On 18. 10. 23, 11:17, Crescent CY Hsieh wrote:
MOXA PCIe boards have 4 serial interfaces and don't require additional
stuff to switch between interfaces:

- RS232
- RS422
- RS485_2W (half-duplex)
- RS485_4W (full-duplex)

By using ioctl command "TIOCRS485", it can switch between default
interface and RS485 if supported.

That means, for RS422/RS485 board, it can switch between RS422 and
RS485 by setting the flags within struct serial_rs485.

However, for the RS232/RS422/RS485 board, it can only switch between
RS232 and RS485, there's no flag for switching interface into RS422.

This patch uses "SER_RS485_TERMINATE_BUS" to represent RS422 as a
workaround solution:

- RS232                   = (no flags are set)
- RS422                   = SER_RS485_ENABLED | SER_RS485_TERMINATE_BUS
- RS485_2W (half-duplex)  = SER_RS485_ENABLED
- RS485_4W (full-duplex)  = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX

Signed-off-by: Crescent CY Hsieh <crescentcy.hsieh@xxxxxxxx>
---
  drivers/tty/serial/8250/8250_pci.c | 58 ++++++++++++++++++++++++++++++
  1 file changed, 58 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 29a28e72b..098ac466b 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1974,6 +1974,10 @@ pci_sunix_setup(struct serial_private *priv,
  #define MOXA_RS485_2W	0x0F
  #define MOXA_UIR_OFFSET	0x04
+static const struct serial_rs485 pci_moxa_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
+};
+
  static bool pci_moxa_is_mini_pcie(unsigned short device)
  {
  	if (device == PCI_DEVICE_ID_MOXA_CP102N	||
@@ -2024,6 +2028,46 @@ static int pci_moxa_set_interface(const struct pci_dev *dev,
  	return 0;
  }
+/*
+ * MOXA PCIe boards support switching the serial interface using the ioctl
+ * command "TIOCSRS485", but there is currently no dedicated flag for switching
+ * to RS422. As a workaround, we utilize the "SER_RS485_TERMINATE_BUS" flag to
+ * represent RS422.
+ *
+ *	RS232			= (no flags are set)
+ *	RS422			= SER_RS485_ENABLED | SER_RS485_TERMINATE_BUS

Oh, I noticed only now. Can we implement this properly? I mean by defining e.g. SER_RS422_ENABLED? And add checks to uart_check_rs485_flags() that only one of 485/422 is set and whatever else makes sense.

+ *	RS485_2W (half-duplex)	= SER_RS485_ENABLED
+ *	RS485_4W (full-duplex)	= SER_RS485_ENABLED | SER_RS485_RX_DURING_TX
+ */

thanks,
--
js
suse labs




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