/* SPDX-FileCopyrightText: 2021 Pali Rohár <pali@kernel.org> */
/* SPDX-License-Identifier: GPL-2.0-or-later */

#include <asm/termbits.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <unistd.h>

#define B(n) { B##n, n }
static
struct { tcflag_t bn; unsigned int n; }
map[] =
{
    B(0), B(50), B(75), B(110), B(134), B(150), B(200), B(300), B(600),
    B(1200), B(1800), B(2400), B(4800), B(9600), B(19200), B(38400),
    B(57600), B(115200), B(230400), B(460800), B(500000), B(576000),
    B(921600), B(1000000), B(1152000), B(1500000), B(2000000),
#ifdef B2500000
    /* non-SPARC architectures support these Bnnn constants */
    B(2500000), B(3000000), B(3500000), B(4000000)
#else
    /* SPARC architecture supports these Bnnn constants */
    B(76800), B(153600), B(307200), B(614400)
#endif
};
#undef B

static
tcflag_t
map_n_to_bn(unsigned int n)
{
    size_t i;

    for (i = 0; i < sizeof(map)/sizeof(map[0]); i++) {
        if (map[i].n == n)
            return map[i].bn;
    }

    return B0;
}

static
unsigned int
map_bn_to_n(tcflag_t bn)
{
    size_t i;

    for (i = 0; i < sizeof(map)/sizeof(map[0]); i++) {
        if (map[i].bn == bn)
            return map[i].n;
    }

    return 0;
}


int
main(int argc, char *argv[])
{
    /* Declare tio structure, its type depends on supported ioctl */
#ifdef TCGETS2
    struct termios2 tio;
#else
    struct termios tio;
#endif
    unsigned int n;
    tcflag_t bn;
    int fd, rc;

    if (argc != 2 && argc != 3 && argc != 4) {
        fprintf(stderr, "Usage: %s device [output [input] ]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY);
    if (fd < 0) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    /* Get the current serial port settings via supported ioctl */
#ifdef TCGETS2
    rc = ioctl(fd, TCGETS2, &tio);
#else
    rc = ioctl(fd, TCGETS, &tio);
#endif
    if (rc) {
        perror("TCGETS");
        close(fd);
        exit(EXIT_FAILURE);
    }

    /* Change baud rate when more arguments were provided */
    if (argc == 3 || argc == 4) {
        /* Clear the current output baud rate and fill a new value */
        n = atoi(argv[2]);
        /* When possible prefer usage of Bnnn constant as glibc-based
           applications are not able to parse BOTHER c_ospeed baud rate */
        bn = map_n_to_bn(n);
        if (n != 0 && bn == B0) {
#ifdef BOTHER
            bn = BOTHER;
#else
            fprintf(stderr, "baud rate %u is unsupported\n", n);
            close(fd);
            exit(EXIT_FAILURE);
#endif
        }
        tio.c_cflag &= ~CBAUD;
        tio.c_cflag |= bn;
#ifdef BOTHER
        tio.c_ospeed = n;
#endif

        /* When 4th argument is not provided reuse output baud rate */
        if (argc == 4) {
            n = atoi(argv[3]);
            bn = map_n_to_bn(n);
            /* Clear the current input baud rate and fill a new value */
            if (n != 0 && bn == B0) {
#ifdef BOTHER
                bn = BOTHER;
#else
                fprintf(stderr, "baud rate %u is unsupported\n", n);
                close(fd);
                exit(EXIT_FAILURE);
#endif
            }
        }

        if ((tio.c_cflag & CBAUD) != bn) {
#ifdef IBSHIFT
            tio.c_cflag &= ~(CBAUD << IBSHIFT);
            tio.c_cflag |= bn << IBSHIFT;
#ifdef BOTHER
            tio.c_ispeed = n;
#endif
#else
            fprintf(stderr, "split baud rates are unsupported\n", n);
            close(fd);
            exit(EXIT_FAILURE);
#endif
        } else {
#ifdef IBSHIFT
            /* B0 sets the input baud to the output baud rate */
            tio.c_cflag &= ~(CBAUD << IBSHIFT);
            tio.c_cflag |= B0 << IBSHIFT;
#ifdef BOTHER
            tio.c_ispeed = 0;
#endif
#endif
        }

        /* Set new serial port settings via supported ioctl */
#ifdef TCSETS2
        rc = ioctl(fd, TCSETS2, &tio);
#else
        rc = ioctl(fd, TCSETS, &tio);
#endif
        if (rc) {
            perror("TCSETS");
            close(fd);
            exit(EXIT_FAILURE);
        }

        /* And get new values which were really configured */
#ifdef TCGETS2
        rc = ioctl(fd, TCGETS2, &tio);
#else
        rc = ioctl(fd, TCGETS, &tio);
#endif
        if (rc) {
            perror("TCGETS");
            close(fd);
            exit(EXIT_FAILURE);
        }
    }

    bn = tio.c_cflag & CBAUD;
#ifdef BOTHER
    if (bn == BOTHER)
        n = tio.c_ospeed;
    else
#endif
        n = map_bn_to_n(bn);
    printf("output baud rate: %u\n", n);

#ifdef IBSHIFT
    bn = (tio.c_cflag >> IBSHIFT) & CBAUD;
    if (bn == B0)
#endif
        bn = tio.c_cflag & CBAUD;
#ifdef BOTHER
    if (bn == BOTHER)
        n = tio.c_ispeed;
    else
#endif
        n = map_bn_to_n(bn);
    printf("input baud rate: %u\n", n);

    close(fd);
    exit(EXIT_SUCCESS);
}