snd_unit2c
#define CHN_CHAN(x) (snd_unit2c((x)->unit))
snd_unit2u(unit), dsp_cdevs[i].sep, snd_unit2c(unit));
(devunit == -1 || snd_unit2c(devunit) < snd_maxautovchans))
(devunit == -1) ? -1 : snd_unit2c(devunit));