MacOS Failed to apply some or all settings

[DonavanMartin]

serial2-rs/src/sys/unix/mod.rs

Line 163 in 4b9413d

pub fn set_configuration(&mut self, settings: &Settings) -> std::io::Result<()> {

I'm unable to connect port with MacOS: "/dev/tty.usbserial-DK0I847P": "ValidationError: StdError(Custom { kind: Other, error: "failed to apply some or all settings" })"

I think their's something misconfigured with baud rate.

Windows and Debian are working properly.

[bailout00]

Same issue here, some notes here:

de-vri-es/serial2-tokio-rs#9

[bailout00]

A bit more info, definitely something around changing the baud rate. Changing any other settings seems to work normally, but changing the baud rate breaks it.

Seems like it might be related to this possibly?

#41

Serial port opened, settings: Settings { baud_rate: Ok(9600), char_size: Ok(Bits8), stop_bits: Ok(One), parity: Ok(None), flow_control: Ok(None) }
Error setting serial port settings: failed to apply some or all settings
Serial settings after set: Settings { baud_rate: Ok(115200), char_size: Ok(Bits8), stop_bits: Ok(One), parity: Ok(None), flow_control: Ok(None) }

match  SerialPort::open("/dev/tty.usbserial-16548", KeepSettings) {
        Ok(mut p) => {
            let mut settings = p.get_configuration().unwrap();
            debug!("Serial port opened, settings: {:?}", settings);
            settings.set_baud_rate(115200);
            let set_result = p.set_configuration(&settings);
            match set_result {
                Ok(_) => {
                    debug!("Serial port settings set: {:?}", settings);
                }
                Err(e) => {
                    println!("Error setting serial port settings: {}", e);
                    let mut settings = p.get_configuration().unwrap();
                    debug!("Serial settings after set: {:?}", settings);
                    
                }
            }
        }
        Err(e) => {
            println!("Error opening serial port {} {}", "/dev/tty.usbserial-14430", e);
        }
    }

Setting it back to 9600 DOES work but so far any other number fails

[de-vri-es]

Argh, I think it must be related to PR #39 (to fix issue #38).

Initial tests seemed to show that the custom speeds set that way are reported back in tcgetattr, but maybe this is not the case, and we read 9600 instead of the custom baud rate.

Sadly, if this is true, then there seems to be no way to retrieve the actual baud rate on OS X after we use the IOCTL_IOSSIOSPEED ioctl. And that means that using it will break get_configuration().

To verify this, you can create the serial port with baud rate 9600, and then change the configuration afterwards. While it will report failure, it might actually have set the baud rate, so you might still be able to use the serial port.

If that works, could you see what get_configuration() reports and what stty -F /dev/your-tty says, while you have your programming running with the serial port opened?

[bailout00]

You're correct

$ stty -f /dev/tty.usbserial-16548
speed 115200 baud;
lflags: -icanon -isig -iexten -echo
iflags: -icrnl -ixon -ixany -imaxbel -brkint
oflags: -opost -onlcr -oxtabs
cflags: cs8 -parenb

And also get_configuration does show the correct speed even after the error message

Yea for now I've ignored the error on macos, the target is linux and so far its fine there so not a huge deal but should maybe be addressed in the lib somehow.

[de-vri-es]

I agree. I wonder is how stty manages to get the correct speed. Is it possible to use something like strace (but mac OS equivalent) to see what syscalls stty is performing?

/edit: Nevermind, I think this was just an oversight in checking the desired and actual speed on Mac OS. I'll try to fix it now.

[de-vri-es]

Could one of you test #45 on an Apple machine? Sadly I don't have access to one :(

[bailout00]

That seems good to me 👍

[de-vri-es]

Did you check if it works as expected? I'm still nervous the speed might not be reported back correctly with tcgetattr.

[bailout00]

Well, I actually can't use it at all on macos. Not sure why but it blocks forever when trying to write a single byte to any usb adapter so not sure I'd be a great test. But it did succeed and stty says the speed changed.

[de-vri-es]

Does it at-least not report an error on opening the serial port or applying the baud rate anymore?

/edit: I also want to figure out that issue, but let's do one at a time 😄

[bailout00]

Correct, no longer throws an error

[de-vri-es]

Thanks for testing it! And thanks @DonavanMartin and @bailout00 for reporting the issue and providing information!

Released as v0.2.28. I will also bump serial2-tokio. 🚀