How to find out which terminal is being configured?

Question

Assume you want to connect your Ubuntu 13.04 desktop computer via TTL-232R-3V3 USB cable to the UART interface of an embedded system running an individual Linux flavor, that does not belong to a major distribution. Your own machine offers you the interface to your connection via /dev/ttyUSB0. Because you are using a framework for a high level language (pySerial) you know that you configure some terminal options via the C-struct termios.

Now the question is, where is that terminal you are configuring? Is that information you send to the remote device and configure that? Or do you simply configure how the /dev/ttyUSB0 interface is interpreted by your system? Or is there maybe even some configuration happening in the logic of the UART-to-USB converter cable? And if all 3 are possible, how would you determine which set of parameters where configured by your termios manipulations on /dev/ttyUSB0?

If it makes things easier to explain, consider the example of LF/CR handling which can contain, depending on the flags you set, either only LF, only CR or both as would be typical for windows. My question is not limited to these options only, though.

Note: I came to that question after I realised that I already saw some options active, that the man page declares as not available in POSIX and Linux.

Answer 1

All the configuration options are settings for the device driver. Most of them are implemented entirely in the driver software, such as echoing, CR-to-LF translation, and raw-vs-cooked mode.

Some of them, such as modes related to RS-232 signals, might be implemented in the device hardware, and the device driver will perform the appropriate device control operations to enable those options.