The PCM's sound.h file only seems to include <sys/tty.h>, because channel_if seems to require selinfo. Just replace it with <sys/selinfo.h>. There's no real problem with including <sys/tty.h> here, even with MPSAFE TTY, but <sys/tty.h> is something that should be used by the TTY layer, its driver and code that integrated it with the process tree.