In my serial_config which I pass to the ioctl() that sets up my 16550A.ko serial port I have set .rx_timeout = 500000 and I am doing non-blocking reads.
This indeed results in a 500us delay when reading a serial port with no incoming bytes, which I can measure precisely on an oscilloscope (I have a DIO port pulse depicting the duration of the read()). This is wasted time in my (RT userspace) app during the read() when there is no serial traffic on a particular port, and I have many serial ports. But why must I decide how long to stall the RT process with a timeout? Can't read() return immediately if there is no data in the device ? Must I use an ioctl with RTSER_RTIOC_GET_STATUS to inspect the UART LSR for data available? (This is a RT userspace app on Xeno 3.1.2, kernel 4.19.229, intel I5, 16550 compat UART) thanks, -C Smith
