hush/libbb/speed_table.c
Denys Vlasenko 525209ac94 libbb/speed_table.c: expand comments
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-09-26 14:37:12 +02:00

184 lines
3.8 KiB
C

/* vi: set sw=4 ts=4: */
/*
* compact speed_t <-> speed functions for busybox
*
* Copyright (C) 2003 Manuel Novoa III <mjn3@codepoet.org>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
#include "libbb.h"
struct speed_map {
#if defined __FreeBSD__ \
|| (defined B115200 && B115200 > 0xffff) \
|| (defined B230400 && B230400 > 0xffff) \
|| (defined B460800 && B460800 > 0xffff) \
|| (defined B921600 && B921600 > 0xffff) \
|| (defined B1152000 && B1152000 > 0xffff) \
|| (defined B1000000 && B1000000 > 0xffff) \
|| (defined B2000000 && B2000000 > 0xffff) \
|| (defined B3000000 && B3000000 > 0xffff) \
|| (defined B4000000 && B4000000 > 0xffff)
/* On FreeBSD, B<num> constants don't fit into a short */
unsigned speed;
#else
unsigned short speed;
#endif
unsigned short value;
};
/* On Linux, Bxx constants are 0..15 (up to B38400) and 0x1001..0x100f */
static const struct speed_map speeds[] = {
{B0, 0},
{B50, 50},
{B75, 75},
{B110, 110},
{B134, 134},
{B150, 150},
{B200, 200},
{B300, 300},
{B600, 600},
{B1200, 1200},
{B1800, 1800},
{B2400, 2400},
{B4800, 4800},
{B9600, 9600},
#ifdef B19200
{B19200, 19200},
#elif defined(EXTA)
{EXTA, 19200},
#endif
/* 19200 = 0x4b00 */
/* 38400 = 0x9600, this value would use bit#15 if not "/200" encoded: */
#ifdef B38400
{B38400, 38400/200 + 0x8000u},
#elif defined(EXTB)
{EXTB, 38400/200 + 0x8000u},
#endif
#ifdef B57600
{B57600, 57600/200 + 0x8000u},
#endif
#ifdef B115200
{B115200, 115200/200 + 0x8000u},
#endif
#ifdef B230400
{B230400, 230400/200 + 0x8000u},
#endif
#ifdef B460800
{B460800, 460800/200 + 0x8000u},
#endif
#ifdef B576000
{B576000, 576000/200 + 0x8000u},
#endif
#ifdef B921600
{B921600, 921600/200 + 0x8000u},
#endif
#ifdef B1152000
{B1152000, 1152000/200 + 0x8000u},
#endif
#ifdef B500000
{B500000, 500000/200 + 0x8000u},
#endif
#ifdef B1000000
{B1000000, 1000000/200 + 0x8000u},
#endif
#ifdef B1500000
{B1500000, 1500000/200 + 0x8000u},
#endif
#ifdef B2000000
{B2000000, 2000000/200 + 0x8000u},
#endif
#ifdef B2500000
{B2500000, 2500000/200 + 0x8000u},
#endif
#ifdef B3000000
{B3000000, 3000000/200 + 0x8000u},
#endif
#ifdef B3500000
{B3500000, 3500000/200 + 0x8000u},
#endif
#ifdef B4000000
{B4000000, 4000000/200 + 0x8000u},
#endif
/* 4000000/200 = 0x4e20, bit#15 still does not interfere with the value */
/* (can use /800 if higher speeds would appear, /1600 won't work for B500000) */
};
/*
* TODO: maybe we can just bite the bullet, ditch the table and use termios2
* Linux API (supports arbitrary baud rates, no Bxxxx mess needed)? Example:
*
* #include <asm/termios.h>
* #include <asm/ioctls.h>
* struct termios2 t;
* ioctl(fd, TCGETS2, &t);
* t.c_ospeed = t.c_ispeed = 543210;
* t.c_cflag &= ~CBAUD;
* t.c_cflag |= BOTHER;
* ioctl(fd, TCSETS2, &t);
*/
enum { NUM_SPEEDS = ARRAY_SIZE(speeds) };
unsigned FAST_FUNC tty_baud_to_value(speed_t speed)
{
int i = 0;
do {
if (speed == speeds[i].speed) {
if (speeds[i].value & 0x8000u) {
return ((unsigned)(speeds[i].value) & 0x7fffU) * 200;
}
return speeds[i].value;
}
} while (++i < NUM_SPEEDS);
return 0;
}
speed_t FAST_FUNC tty_value_to_baud(unsigned int value)
{
int i = 0;
do {
if (value == tty_baud_to_value(speeds[i].speed)) {
return speeds[i].speed;
}
} while (++i < NUM_SPEEDS);
return (speed_t) - 1;
}
#if 0
/* testing code */
#include <stdio.h>
int main(void)
{
unsigned long v;
speed_t s;
for (v = 0 ; v < 1000000; v++) {
s = tty_value_to_baud(v);
if (s == (speed_t) -1) {
continue;
}
printf("v = %lu -- s = %0lo\n", v, (unsigned long) s);
}
printf("-------------------------------\n");
for (s = 0 ; s < 010017+1; s++) {
v = tty_baud_to_value(s);
if (!v) {
continue;
}
printf("v = %lu -- s = %0lo\n", v, (unsigned long) s);
}
return 0;
}
#endif