return changed;
 }
 
-static struct snd_kcontrol_new roland_load_ctl = {
+static const struct snd_kcontrol_new roland_load_ctl = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "MIDI Input Mode",
        .info = roland_load_info,
 
 };
 
 /* the read-only variant */
-static struct snd_kcontrol_new usb_feature_unit_ctl_ro = {
+static const struct snd_kcontrol_new usb_feature_unit_ctl_ro = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "", /* will be filled later manually */
        .info = mixer_ctl_feature_info,
 }
 
 /* alsa control interface for processing/extension unit */
-static struct snd_kcontrol_new mixer_procunit_ctl = {
+static const struct snd_kcontrol_new mixer_procunit_ctl = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "", /* will be filled later */
        .info = mixer_ctl_feature_info,
 }
 
 /* alsa control interface for selector unit */
-static struct snd_kcontrol_new mixer_selectunit_ctl = {
+static const struct snd_kcontrol_new mixer_selectunit_ctl = {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "", /* will be filled later */
        .info = mixer_ctl_selector_info,