refactor(rs485): refactor Linux RS485 related code

serial.go

@@ -101,23 +101,6 @@ type Mode struct {
 	Parity            Parity           // Parity (see Parity type for more info)
 	StopBits          StopBits         // Stop bits (see StopBits type for more info)
 	InitialStatusBits *ModemOutputBits // Initial output modem bits status (if nil defaults to DTR=true and RTS=true)
-	RS485             RS485Config      // RS485 configuration
-}
-
-// RS485Config -- platform independent RS485 config. Thie structure is ignored unless Enable is true.
-type RS485Config struct {
-	// Enable RS485 support
-	Enabled bool
-	// Delay RTS prior to send
-	DelayRtsBeforeSend time.Duration
-	// Delay RTS after send
-	DelayRtsAfterSend time.Duration
-	// Set RTS high during send
-	RtsHighDuringSend bool
-	// Set RTS high after send
-	RtsHighAfterSend bool
-	// Rx during Tx
-	RxDuringTx bool
 }
 
 // Parity describes a serial port parity setting

serial_rs485_linux.go

@@ -0,0 +1,39 @@
+//go:build linux
+
+package serial
+
+import (
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	rs485Enabled      = 1 << 0
+	rs485RTSOnSend    = 1 << 1
+	rs485RTSAfterSend = 1 << 2
+	rs485RXDuringTX   = 1 << 4
+	rs485Tiocs        = unix.TIOCSRS485
+)
+
+// EnableRS485 enables RS485 functionality of driver via an ioctl if the config says so
+func (port *unixPort) EnableRS485(config *LinuxRS485Config) error {
+	rs485 := rs485IoctlOpts{
+		rs485Enabled,
+		int(config.DelayRtsBeforeSend / time.Millisecond),
+		int(config.DelayRtsAfterSend / time.Millisecond),
+		[5]int{0, 0, 0, 0, 0},
+	}
+
+	if config.RtsHighDuringSend {
+		rs485.flags |= rs485RTSOnSend
+	}
+	if config.RtsHighAfterSend {
+		rs485.flags |= rs485RTSAfterSend
+	}
+	if config.RxDuringTx {
+		rs485.flags |= rs485RXDuringTX
+	}
+
+	return unix.IoctlSetPointerInt(port.handle, rs485Tiocs, rs485.flags)
+}

serial_rs485_stub.go

@@ -0,0 +1,11 @@
+//go:build darwin || freebsd || openbsd
+
+package serial
+
+import (
+	"fmt"
+)
+
+func (port *unixPort) EnableRS485(config *LinuxRS485Config) error {
+	return fmt.Errorf("EnableRS485 is not supported on this OS")
+}

serial_rs485_unix.go

@@ -0,0 +1,20 @@
+//go:build linux || darwin || freebsd || openbsd
+
+package serial
+
+import "time"
+
+// RS485Config holds configuration for RS485 mode on Linux systems (TIOCSRS485).
+// Note: This is only supported on Linux systems.
+type LinuxRS485Config struct {
+	// Delay RTS prior to send
+	DelayRtsBeforeSend time.Duration
+	// Delay RTS after send
+	DelayRtsAfterSend time.Duration
+	// Set RTS high during send
+	RtsHighDuringSend bool
+	// Set RTS high after send
+	RtsHighAfterSend bool
+	// Rx during Tx
+	RxDuringTx bool
+}

serial_unix.go

@@ -29,14 +29,6 @@ type unixPort struct {
 	opened      uint32
 }
 
-const (
-	rs485Enabled      = 1 << 0
-	rs485RTSOnSend    = 1 << 1
-	rs485RTSAfterSend = 1 << 2
-	rs485RXDuringTX   = 1 << 4
-	rs485Tiocs        = 0x542f // unix.TIOCSRS485 is not supported on MacOS
-)
-
 // rs485_ioctl_opts is used to configure RS485 options in the driver
 type rs485IoctlOpts struct {
 	flags              int
@@ -295,12 +287,6 @@ func nativeOpen(portName string, mode *Mode) (*unixPort, error) {
 
 	port.acquireExclusiveAccess()
 
-	// Enable RS485, if requested
-	if err = port.enableRS485(&mode.RS485); err != nil {
-		port.Close()
-		return nil, err
-	}
-
 	// This pipe is used as a signal to cancel blocking Read
 	pipe := &unixutils.Pipe{}
 	if err := pipe.Open(); err != nil {
@@ -487,28 +473,3 @@ func (port *unixPort) acquireExclusiveAccess() error {
 func (port *unixPort) releaseExclusiveAccess() error {
 	return unix.IoctlSetInt(port.handle, unix.TIOCNXCL, 0)
 }
-
-// enableRS485 enables RS485 functionality of driver via an ioctl if the config says so
-func (port *unixPort) enableRS485(config *RS485Config) error {
-	if !config.Enabled {
-		return nil
-	}
-	rs485 := rs485IoctlOpts{
-		rs485Enabled,
-		int(config.DelayRtsBeforeSend / time.Millisecond),
-		int(config.DelayRtsAfterSend / time.Millisecond),
-		[5]int{0, 0, 0, 0, 0},
-	}
-
-	if config.RtsHighDuringSend {
-		rs485.flags |= rs485RTSOnSend
-	}
-	if config.RtsHighAfterSend {
-		rs485.flags |= rs485RTSAfterSend
-	}
-	if config.RxDuringTx {
-		rs485.flags |= rs485RXDuringTX
-	}
-
-	return unix.IoctlSetPointerInt(port.handle, rs485Tiocs, rs485.flags)
-}