mix_getrecdevs
r = mix_getrecdevs(sc->sm);
mix_setrecdevs(m, mix_getrecdevs(m) | (1 << SOUND_MIXER_SYNTH));
mix_setrecdevs(m, mix_getrecdevs(m) &
src &= mix_getrecdevs(m);
return (mix_getrecdevs(m));
v = mix_getrecdevs(m);
u_int32_t mix_getrecdevs(struct snd_mixer *m);