Should I use stereo audio files or mono audio files for each asio output channel?

This is my frist time to play with asio sdk. I run “hostsample.cpp” with vs2015 and It works fine.But I have to copy stereo audio files’ data(LRLRLR) to asio’s buffers, and it only outputs right channel’s data from audio files. Is that true or it just because I use “ASIO4all”?

case ASIOSTInt32LSB:
//memset(asioDriverInfo.bufferInfos[i].buffers[index], 0, buffSize * 4);
memcpy(asioDriverInfo.bufferInfos[i].buffers[index], myfileserv->data, buffSize * 4);