- shm->buffer = (unsigned char *) mmap(NULL, info.fragstotal
- * info.fragsize, PROT_WRITE, MAP_FILE|MAP_SHARED, audio_fd, 0);
+ // memory map the dma buffer
+ shm->bufferlength = info.fragstotal * info.fragsize;
+ shm->buffer = (unsigned char *) mmap(NULL, shm->bufferlength, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED, audio_fd, 0);