Set baud rate using cfsetispeed

[kjaved0]

On Ubuntu 25.10 running on framework desktop (Ryzen 395+) with CH341 / CH340, the way the original code sets the baud rate does not work.

Using cfsetospeed and cfsetispeed instead works as it should.

[gemini-code-assist]

Summary of Changes

Hello @kjaved0, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical issue where serial port baud rate configuration failed on certain Linux systems, specifically Ubuntu 25.10 when using CH341/CH340 devices. The change ensures robust serial communication by adopting standard POSIX functions (cfsetispeed and cfsetospeed) for setting the baud rate, thereby improving compatibility and reliability across different environments.

Highlights

• Baud Rate Configuration Fix: The method for setting the serial port baud rate has been updated to resolve compatibility issues on specific Linux environments, particularly Ubuntu 25.10 with CH34x devices.
• Portable Baud Rate Setting: The direct assignment of cflag_baud to newtio.c_cflag has been replaced with the use of cfsetispeed and cfsetospeed functions for setting input and output baud rates, which are more portable and reliable.

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[gemini-code-assist]

Code Review

This pull request improves baud rate setting on Linux by using the more portable cfsetispeed and cfsetospeed functions. This is a good change that should improve compatibility as described. I have one suggestion to add error handling for these new function calls to make the implementation more robust. Additionally, it appears the same logic exists in the C language implementation of the SDK (c/src/dynamixel_sdk/port_handler_linux.c). The setupPortLinux function in that file should also be updated with this new method for setting the baud rate to maintain consistency between the C and C++ APIs.

[gemini-code-assist]

The return values of cfsetispeed and cfsetospeed should be checked to ensure the baud rate was set successfully. These functions return -1 on error. Failing to set the baud rate will cause all subsequent communication to fail silently, which can be difficult to debug. It's better to fail early with a clear error message.

  if (cfsetispeed(&newtio, cflag_baud) < 0 || cfsetospeed(&newtio, cflag_baud) < 0)
  {
    printf("[PortHandlerLinux::SetupPort] Error setting baud rate!\n");
    return false;
  }