oss_digital_control
rv = sndctl_dsp_readctl(c, (oss_digital_control *)data);
rv = sndctl_dsp_writectl(c, (oss_digital_control *)data);
sndctl_dsp_readctl(audio_client_t *c, oss_digital_control *ctl)
sndctl_dsp_writectl(audio_client_t *c, oss_digital_control *ctl)
#define SNDCTL_DSP_READCTL __OSSIOWR('P', 26, oss_digital_control)
#define SNDCTL_DSP_WRITECTL __OSSIOWR('P', 27, oss_digital_control)