refactor: move LinuxCSerialStruct definition to a shared file

serial_setserial_linux.go

@@ -1,76 +1,33 @@
 //go:build linux
-// +build linux
 
 package serial
 
 import (
 	"fmt"
-	"os"
 	"syscall"
 	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
 
-// CSerialStruct is a C-interop struct for linux/serial.h: struct serial_struct
-// Field order and types must exactly match the C definition for binary compatibility.
-// See: https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/serial.h#L135
-type CSerialStruct struct {
-	Type          int32
-	Line          int32
-	Port          uint32
-	IRQ           int32
-	Flags         int32
-	XmitFifoSize  int32
-	CustomDivisor int32
-	BaudBase      int32
-	CloseDelay    uint16
-	IOType        byte
-	ReservedChar  byte
-	Hub6          int32
-	ClosingWait   uint16
-	ClosingWait2  uint16
-	IOMemBase     uintptr
-	IOMemRegShift uint16
-	PortHigh      uint32
-	// IOMapBase: In C, this is 'unsigned long'. Use uint64 for 64-bit systems.
-	// For 32-bit systems, you may need to use uint32 for binary compatibility.
-	IOMapBase uint64
-}
-
 // GetSerialStruct opens the device and retrieves the CSerialStruct using TIOCGSERIAL ioctl.
-func GetSerialStruct(device string) (*CSerialStruct, error) {
-	f, err := os.OpenFile(device, os.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK, 0666)
-	if err != nil {
-		return nil, fmt.Errorf("failed to open device: %w", err)
-	}
-	defer f.Close()
-
-	var ser CSerialStruct
-	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), unix.TIOCGSERIAL, uintptr(unsafe.Pointer(&ser)))
+func (port *unixPort) GetSerialStruct() (*LinuxCSerialStruct, error) {
+	var ser LinuxCSerialStruct
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(port.handle), unix.TIOCGSERIAL, uintptr(unsafe.Pointer(&ser)))
 	if errno != 0 {
 		return nil, fmt.Errorf("ioctl TIOCGSERIAL failed: %v", errno)
 	}
 	return &ser, nil
 }
 
 // SetSerialPortMode sets the port mode using ioctl TIOCSSERIAL
-func SetSerialPortMode(device string, portMode uint32) error {
-	f, err := os.OpenFile(device, os.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK, 0666)
+func (port *unixPort) SetSerialPortMode(portMode uint32) error {
+	ser, err := port.GetSerialStruct()
 	if err != nil {
-		return fmt.Errorf("failed to open device: %w", err)
+		return err
 	}
-	defer f.Close()
-
-	var ser CSerialStruct
-	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), unix.TIOCGSERIAL, uintptr(unsafe.Pointer(&ser)))
-	if errno != 0 {
-		return fmt.Errorf("ioctl TIOCGSERIAL failed: %v", errno)
-	}
-
 	ser.Port = portMode
-
-	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), unix.TIOCSSERIAL, uintptr(unsafe.Pointer(&ser)))
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(port.handle), unix.TIOCSSERIAL, uintptr(unsafe.Pointer(&ser)))
 	if errno != 0 {
 		return fmt.Errorf("ioctl TIOCSSERIAL failed: %v", errno)
 	}

serial_setserial_linux_test.go

@@ -1,5 +1,4 @@
 //go:build linux
-// +build linux
 
 package serial
 
@@ -28,7 +27,11 @@ func TestGetSerialStructOnFakeTty(t *testing.T) {
 	cmd := startSocatAndWaitForSetserialTest(t, ctx)
 	go cmd.Wait()
 
-	ser, err := GetSerialStruct("/tmp/faketty_setserial")
+	port, err := nativeOpen("/tmp/faketty", &Mode{})
+	require.NoError(t, err)
+	defer port.Close()
+	ser, err := port.GetSerialStruct()
+
 	// Note: socat's virtual TTY may not fully support TIOCGSERIAL.
 	// If not supported, skip the test (environment dependent).
 	if err != nil {
@@ -43,7 +46,10 @@ func TestSetSerialPortModeOnFakeTty(t *testing.T) {
 	cmd := startSocatAndWaitForSetserialTest(t, ctx)
 	go cmd.Wait()
 
-	err := SetSerialPortMode("/tmp/faketty_setserial", 0)
+	port, err := nativeOpen("/tmp/faketty", &Mode{})
+	require.NoError(t, err)
+	defer port.Close()
+	err = port.SetSerialPortMode(0)
 	// Note: socat's virtual TTY may not fully support TIOCSSERIAL.
 	// If not supported, skip the test (environment dependent).
 	if err != nil {

serial_setserial_stub.go

@@ -0,0 +1,12 @@
+//go:build darwin || freebsd || openbsd
+
+package serial
+
+import "fmt"
+
+func (port *unixPort) SetSerialPortMode(portMode uint32) error {
+	return fmt.Errorf("SetSerialPortMode is not supported on this OS")
+}
+func (port *unixPort) GetSerialStruct() (*LinuxCSerialStruct, error) {
+	return nil, fmt.Errorf("GetSerialStruct is not supported on this OS")
+}

serial_setserial_unix.go

@@ -0,0 +1,28 @@
+//go:build linux || darwin || freebsd || openbsd
+
+package serial
+
+// LinuxCSerialStruct is a C-interop struct for linux/serial.h: struct serial_struct
+// Field order and types must exactly match the C definition for binary compatibility.
+// See: https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/serial.h#L135
+type LinuxCSerialStruct struct {
+	Type          int32
+	Line          int32
+	Port          uint32
+	IRQ           int32
+	Flags         int32
+	XmitFifoSize  int32
+	CustomDivisor int32
+	BaudBase      int32
+	CloseDelay    uint16
+	IOType        byte
+	ReservedChar  byte
+	Hub6          int32
+	ClosingWait   uint16
+	ClosingWait2  uint16
+	IOMemBase     uintptr
+	IOMemRegShift uint16
+	PortHigh      uint32
+	// IOMapBase: In C, this is 'unsigned long'.
+	IOMapBase uint
+}