serial_linux.go

//
// Copyright 2014-2024 Cristian Maglie. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//

package serial

import (
	"regexp"

	"golang.org/x/sys/unix"
)

const devFolder = "/dev"

var osPortFilter = regexp.MustCompile("(ttyS|ttyHS|ttyUSB|ttyACM|ttyAMA|rfcomm|ttyO|ttymxc)[0-9]{1,3}")

// termios manipulation functions

var baudrateMap = map[int]uint32{
	0:       unix.B9600, // Default to 9600
	50:      unix.B50,
	75:      unix.B75,
	110:     unix.B110,
	134:     unix.B134,
	150:     unix.B150,
	200:     unix.B200,
	300:     unix.B300,
	600:     unix.B600,
	1200:    unix.B1200,
	1800:    unix.B1800,
	2400:    unix.B2400,
	4800:    unix.B4800,
	9600:    unix.B9600,
	19200:   unix.B19200,
	38400:   unix.B38400,
	57600:   unix.B57600,
	115200:  unix.B115200,
	230400:  unix.B230400,
	460800:  unix.B460800,
	500000:  unix.B500000,
	576000:  unix.B576000,
	921600:  unix.B921600,
	1000000: unix.B1000000,
	1152000: unix.B1152000,
	1500000: unix.B1500000,
	2000000: unix.B2000000,
	2500000: unix.B2500000,
	3000000: unix.B3000000,
	3500000: unix.B3500000,
	4000000: unix.B4000000,
}

var databitsMap = map[int]uint32{
	0: unix.CS8, // Default to 8 bits
	5: unix.CS5,
	6: unix.CS6,
	7: unix.CS7,
	8: unix.CS8,
}

const tcCMSPAR = unix.CMSPAR
const tcIUCLC = unix.IUCLC

const tcCRTSCTS uint32 = unix.CRTSCTS

const ioctlTcgetattr = unix.TCGETS
const ioctlTcsetattr = unix.TCSETS
const ioctlTcflsh = unix.TCFLSH
const ioctlTioccbrk = unix.TIOCCBRK
const ioctlTiocsbrk = unix.TIOCSBRK

func toTermiosSpeedType(speed uint32) uint32 {
	return speed
}

func setTermSettingsBaudrate(speed int, settings *unix.Termios) (error, bool) {
	baudrate, ok := baudrateMap[speed]
	if !ok {
		return nil, true
	}
	// revert old baudrate
	for _, rate := range baudrateMap {
		settings.Cflag &^= rate
	}
	// set new baudrate
	settings.Cflag |= baudrate
	settings.Ispeed = toTermiosSpeedType(baudrate)
	settings.Ospeed = toTermiosSpeedType(baudrate)
	return nil, false
}

func (port *unixPort) Drain() error {
	// It's not super well documented, but this is the same as calling tcdrain:
	// - https://git.musl-libc.org/cgit/musl/tree/src/termios/tcdrain.c
	// - https://elixir.bootlin.com/linux/v6.2.8/source/drivers/tty/tty_io.c#L2673
	return unix.IoctlSetInt(port.handle, unix.TCSBRK, 1)
}