return 1;
 }
 
-static struct snd_kcontrol_new ad1983_auto_smux_mixer = {
+static const struct snd_kcontrol_new ad1983_auto_smux_mixer = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "IEC958 Playback Source",
        .info = ad1983_auto_smux_enum_info,
        return 1;
 }
 
-static struct snd_kcontrol_new ad1988_auto_smux_mixer = {
+static const struct snd_kcontrol_new ad1988_auto_smux_mixer = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "IEC958 Playback Source",
        .info = ad1988_auto_smux_enum_info,
 
                                     &spec->cur_smux[smux_idx]);
 }
 
-static struct snd_kcontrol_new stac_smux_mixer = {
+static const struct snd_kcontrol_new stac_smux_mixer = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "IEC958 Playback Source",
        /* count set later */