SND_BBFPRO_MIXER_IDX_MASK
idx = index & SND_BBFPRO_MIXER_IDX_MASK;
idx = kcontrol->private_value & SND_BBFPRO_MIXER_IDX_MASK;
u16 idx = pv & SND_BBFPRO_MIXER_IDX_MASK;
knew.private_value = index & SND_BBFPRO_MIXER_IDX_MASK;