After opening the port, when trying to set custom baud rate (125000 in my case) the setBaudRate() returns true and no errors are reported, but when I transmit the frequency it is 115200 bps (tested with an oscilloscope). The baudRate() return a frequency of 125000 even after a write...

I debugged the library internals (setBaudRate() of class QSerialPortPrivate in file qserialport_unix.cpp) and I see that the variables inputBaudRate and outputBaudRate of the class QSerialPortPrivateData are always set to 115200. The value of baud_base of the object currentSerialInfo is always set to 115200.

I suppose that this issue depends on a physical limit of my hardware, but I don't know the frequency of the oscillator attached to my board, and this issue came also on my ubuntu desktop...

I think that if there will be a limit in the hardware the software can never overcome it, but I expect that the library returns me an error when I try to set an unsupported baud rate.