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Add a mecanism to prevent unnecessary tcsetattr on changing state

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Add a mechanism of tty_tcsetattr to skip the mode change and omit the
configuration change when the value of the termios structure does not
change.

In the cygwin environment, tcsetattr() resets DTR/RTS to their default
values.
Furthermore, add a mechanism of tty_tcsetattr to revert to the state
before tcsetattr() was called.
However, this method will still cause DTR/RTS spikes.
This commit is contained in:
yabu76 2026-03-14 14:39:50 +09:00
parent 0d1eaef794
commit 9703c25503
1 changed files with 75 additions and 11 deletions
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86
src/tty.c
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@ -179,6 +179,7 @@ static struct termios tio, tio_raw, tio_old, stdout_new, stdout_old, stdin_new,
unsigned long rx_total = 0, tx_total = 0;
static bool connected = false;
static bool standard_baudrate = true;
static bool tty_tcsetattr_first = true;
static void (*printchar)(char c);
static int device_fd;
static char hex_chars[2];
@ -256,28 +257,46 @@ raw_t tty_get_raw_mode(void)
}
}
/* Activate or change port settings */
int tty_tcsetattr(int fd)
{
static struct termios tio_cur;
static int baudrate_cur;
if ( ! connected )
{
return -1;
}
/* Activate or change port settings */
int status;
int ret = 0;
raw_t raw = tty_get_raw_mode();
if (raw == RAW_OFF)
{
status = tcsetattr(fd, TCSANOW, &tio);
struct termios *tiop = (raw == RAW_OFF) ? &tio : &tio_raw;
/* If no need to change, no-op and return */
if (tty_tcsetattr_first == false &&
memcmp(&tio_cur, tiop, sizeof(struct termios)) == 0 &&
baudrate_cur == option.baudrate) {
tio_debug_printf("same termios. skip tty_tcsetattr.");
return 0;
}
else
#if defined(__CYGWIN__)
int line_state;
/* save line state for buggy tcsetattr */
if (ioctl(fd, TIOCMGET, &line_state) < 0)
{
status = tcsetattr(fd, TCSANOW, &tio_raw);
tio_warning_printf("Could not get line state (%s)", strerror(errno));
return -1;
}
if (status == -1)
#endif
if (tcsetattr(fd, TCSANOW, tiop) == -1)
{
tio_error_printf_silent("Could not apply port settings (%s)", strerror(errno));
return -1;
tty_tcsetattr_first = true;
ret = -1;
goto tcsetattr_error_end;
}
/* Set arbitrary baudrate (only works on supported platforms) */
@ -286,11 +305,55 @@ int tty_tcsetattr(int fd)
if (setspeed(device_fd, option.baudrate) != 0)
{
tio_error_printf_silent("Could not set baudrate speed (%s)", strerror(errno));
return -1;
tty_tcsetattr_first = true;
ret = -1;
goto setspeed_error_end;
}
}
return 0;
/* Port settings changed successfully */
memcpy(&tio_cur, tiop, sizeof(tio_cur));
baudrate_cur = option.baudrate;
tty_tcsetattr_first = false;
tcsetattr_error_end:
setspeed_error_end:
#if defined(__CYGWIN__)
/* restore line state for buggy tcsetattr */
if (option.flow == FLOW_HARD)
{
/* hardware flow control */
/* touch DTR only, don't touch RTS */
int tiocm_dtr = TIOCM_DTR;
int action = (line_state & TIOCM_DTR) ? TIOCMBIS /* DTR=LOW */ : TIOCMBIC /* DTR=HIGH */ ;
tio_debug_printf("hard flow : tiocm_dtr=%c, action=%c",
(line_state & TIOCM_DTR) ? '1' : '0', (line_state & TIOCM_DTR) ? 'C' : 'S');
if (ioctl(fd, action, &tiocm_dtr) < 0)
{
tio_warning_printf("Could not set line state (%s)", strerror(errno));
ret = -1;
}
}
else
{
/* not hardware flow control */
/* restore DTR and RTS at the same time */
tio_debug_printf("non-hard flow : line_state=0x%x, TIOCM_DTR=0x%x, TIOCM_RTS=0x%x",
line_state, TIOCM_DTR, TIOCM_RTS);
if (ioctl(fd, TIOCMSET, &line_state) < 0)
{
tio_warning_printf("Could not set line state (%s)", strerror(errno));
ret = -1;
}
}
#endif
return ret;
}
void tty_sync(int fd)
@ -2951,6 +3014,7 @@ int tty_connect(void)
}
/* Activate new port settings and set speed for non-interactive phase */
tty_tcsetattr_first = true;
status = tty_tcsetattr(device_fd);
if (status == -1)
{