soapySDR writeStream question

Hi, i’m writing a Producer/Consumer two thread application around a ring buffer.
Producer insert data into the ring in chunk after some operations of upsampling, FIR filtering
and data conditioning. The consumer simply get frames from the ring and pass that to LimeSDRmini with data units multiples of MTU value. In the writeStream method specification in the Documentation i found

virtual int SoapySDR::Device::writeStream ( Stream * stream,
const void *const * buffs,
const size_t numElems,
int & flags,
const long long timeNs = 0,
const long timeoutUs = 100000

I guess i don’t understand well the roles player by the two parameters timeNs and timeoutUs and so i don’t know how to set them in my specific application. I found some examples where this two parameters are set to zero, but when they should be specified and what is their purpose ?
Tnx for any help. Fabio

Since this looks like a SoapySDR matter, you could try asking in the Pothos group.!topic/pothos-users/