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Fix hang on TTY read #192

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Fix hang on TTY read #192

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7 changes: 7 additions & 0 deletions src/posix/termios.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ use crate::{DataBits, FlowControl, Parity, Result, StopBits};
use nix::libc;

use std::os::unix::prelude::*;
use std::time::Duration;

cfg_if! {
if #[cfg(any(
Expand Down Expand Up @@ -183,6 +184,12 @@ pub(crate) fn set_flow_control(termios: &mut Termios, flow_control: FlowControl)
};
}

pub(crate) fn set_timeout(termios: &mut Termios, timeout: Duration) {
let timeout = u128::min(timeout.as_millis() / 100, u8::MAX as u128) as u8;
termios.c_cc[libc::VMIN as usize] = 0;
termios.c_cc[libc::VTIME as usize] = timeout;
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The description (and the documentation of termios as well) mention setting VTIME to 0 as well. What's the reason for setting it to timeout here?

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I made this utils function to bridge how timeouts are set on termios (by setting VTIME to a value with 100ms steps) with the Duration type on rust.
If you check at

serialport-rs/src/posix/tty.rs

Line 181 in 8961365

termios::set_timeout(&mut termios, Duration::from_millis(0));
, this function is being called with a duration = 0, which means that VTIME is set to zero.

}

pub(crate) fn set_data_bits(termios: &mut Termios, data_bits: DataBits) {
let size = match data_bits {
DataBits::Five => libc::CS5,
Expand Down
6 changes: 5 additions & 1 deletion src/posix/tty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -134,7 +134,9 @@ impl TTYPort {
nix::errno::Errno::result(unsafe { tcgetattr(fd.0, termios.as_mut_ptr()) })?;
let mut termios = unsafe { termios.assume_init() };

// setup TTY for binary serial port access
// Setup TTY for binary serial port access
// Enable non-canonical mode
termios.c_lflag &= !libc::ICANON;
// Enable reading from the port and ignore all modem control lines
termios.c_cflag |= libc::CREAD | libc::CLOCAL;
// Enable raw mode which disables any implicit processing of the input or output data streams
Expand Down Expand Up @@ -175,6 +177,8 @@ impl TTYPort {
termios::set_flow_control(&mut termios, builder.flow_control);
termios::set_data_bits(&mut termios, builder.data_bits);
termios::set_stop_bits(&mut termios, builder.stop_bits);
// Set termios read to non-blocking, as we handle blocking ourselves (with unix::poll)
termios::set_timeout(&mut termios, Duration::from_millis(0));
#[cfg(not(any(target_os = "ios", target_os = "macos")))]
termios::set_baud_rate(&mut termios, builder.baud_rate);
#[cfg(any(target_os = "ios", target_os = "macos"))]
Expand Down
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