ALSA: scarlett2: Add support for software-controllable input gain

Some devices in the Scarlett Gen 4 series have support for
software-controllable input gain. Along with this comes a channel
select option, an auto-gain feature, "safe" mode, and linking two
channels into a stereo pair.

Mark the new scarlett2_notify_input_*() functions with __always_unused
until they get used when the Gen 4 notification callback function
arrays are added.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/fc39e80bb39863dd1579d342097203942b4f3034.1703612638.git.g@b4.vu

1 files changed, 795 insertions, 1 deletions

diff --git a/sound/usb/mixer_scarlett2.c b/sound/usb/mixer_scarlett2.c
index 1a955a6decf3..ab42d8f90e46 100644
--- a/sound/usb/mixer_scarlett2.c
+++ b/sound/usb/mixer_scarlett2.c
@@ -164,6 +164,7 @@
 
 /* some gui mixers can't handle negative ctl values */
 #define SCARLETT2_VOLUME_BIAS 127
+#define SCARLETT2_GAIN_BIAS 70
 
 /* mixer range from -80dB to +6dB in 0.5dB steps */
 #define SCARLETT2_MIXER_MIN_DB -80
@@ -196,11 +197,12 @@ static const u16 scarlett2_mixer_values[SCARLETT2_MIXER_VALUE_COUNT] = {
 /* Maximum number of analogue outputs */
 #define SCARLETT2_ANALOGUE_MAX 10
 
-/* Maximum number of level and pad switches */
+/* Maximum number of various input controls */
 #define SCARLETT2_LEVEL_SWITCH_MAX 2
 #define SCARLETT2_PAD_SWITCH_MAX 8
 #define SCARLETT2_AIR_SWITCH_MAX 8
 #define SCARLETT2_PHANTOM_SWITCH_MAX 2
+#define SCARLETT2_INPUT_GAIN_MAX 2
 
 /* Maximum number of inputs to the mixer */
 #define SCARLETT2_INPUT_MIX_MAX 25
@@ -266,6 +268,16 @@ static const char *const scarlett2_dim_mute_names[SCARLETT2_DIM_MUTE_COUNT] = {
 	"Mute Playback Switch", "Dim Playback Switch"
 };
 
+/* Autogain Status Values */
+enum {
+	SCARLETT2_AUTOGAIN_STATUS_STOPPED,
+	SCARLETT2_AUTOGAIN_STATUS_RUNNING,
+	SCARLETT2_AUTOGAIN_STATUS_FAILED,
+	SCARLETT2_AUTOGAIN_STATUS_CANCELLED,
+	SCARLETT2_AUTOGAIN_STATUS_UNKNOWN,
+	SCARLETT2_AUTOGAIN_STATUS_COUNT
+};
+
 /* Notification callback functions */
 struct scarlett2_notification {
 	u32 mask;
@@ -316,6 +328,12 @@ enum {
 	SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH,
 	SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE,
 	SCARLETT2_CONFIG_TALKBACK_MAP,
+	SCARLETT2_CONFIG_AUTOGAIN_SWITCH,
+	SCARLETT2_CONFIG_AUTOGAIN_STATUS,
+	SCARLETT2_CONFIG_INPUT_GAIN,
+	SCARLETT2_CONFIG_SAFE_SWITCH,
+	SCARLETT2_CONFIG_INPUT_SELECT_SWITCH,
+	SCARLETT2_CONFIG_INPUT_LINK_SWITCH,
 	SCARLETT2_CONFIG_COUNT
 };
 
@@ -662,6 +680,9 @@ struct scarlett2_device_info {
 	/* the number of inputs each phantom switch controls */
 	u8 inputs_per_phantom;
 
+	/* the number of inputs with software-controllable gain */
+	u8 gain_input_count;
+
 	/* the number of direct monitor options
 	 * (0 = none, 1 = mono only, 2 = mono/stereo)
 	 */
@@ -722,6 +743,10 @@ struct scarlett2_data {
 	u8 input_pad_updated;
 	u8 input_air_updated;
 	u8 input_phantom_updated;
+	u8 input_select_updated;
+	u8 input_gain_updated;
+	u8 autogain_updated;
+	u8 input_safe_updated;
 	u8 monitor_other_updated;
 	u8 direct_monitor_updated;
 	u8 mux_updated;
@@ -737,6 +762,12 @@ struct scarlett2_data {
 	u8 air_switch[SCARLETT2_AIR_SWITCH_MAX];
 	u8 phantom_switch[SCARLETT2_PHANTOM_SWITCH_MAX];
 	u8 phantom_persistence;
+	u8 input_select_switch;
+	u8 input_link_switch[SCARLETT2_INPUT_GAIN_MAX / 2];
+	u8 gain[SCARLETT2_INPUT_GAIN_MAX];
+	u8 autogain_switch[SCARLETT2_INPUT_GAIN_MAX];
+	u8 autogain_status[SCARLETT2_INPUT_GAIN_MAX];
+	u8 safe_switch[SCARLETT2_INPUT_GAIN_MAX];
 	u8 direct_monitor_switch;
 	u8 speaker_switching_switch;
 	u8 talkback_switch;
@@ -754,6 +785,12 @@ struct scarlett2_data {
 	struct snd_kcontrol *pad_ctls[SCARLETT2_PAD_SWITCH_MAX];
 	struct snd_kcontrol *air_ctls[SCARLETT2_AIR_SWITCH_MAX];
 	struct snd_kcontrol *phantom_ctls[SCARLETT2_PHANTOM_SWITCH_MAX];
+	struct snd_kcontrol *input_select_ctl;
+	struct snd_kcontrol *input_link_ctls[SCARLETT2_INPUT_GAIN_MAX / 2];
+	struct snd_kcontrol *input_gain_ctls[SCARLETT2_INPUT_GAIN_MAX];
+	struct snd_kcontrol *autogain_ctls[SCARLETT2_INPUT_GAIN_MAX];
+	struct snd_kcontrol *autogain_status_ctls[SCARLETT2_INPUT_GAIN_MAX];
+	struct snd_kcontrol *safe_ctls[SCARLETT2_INPUT_GAIN_MAX];
 	struct snd_kcontrol *mux_ctls[SCARLETT2_MUX_MAX];
 	struct snd_kcontrol *direct_monitor_ctl;
 	struct snd_kcontrol *speaker_switching_ctl;
@@ -2352,6 +2389,610 @@ static int scarlett2_add_sync_ctl(struct usb_mixer_interface *mixer)
 				     0, 1, "Sync Status", &private->sync_ctl);
 }
 
+/*** Autogain Switch and Status Controls ***/
+
+static int scarlett2_update_autogain(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int err, i;
+	u8 raw_autogain_status[SCARLETT2_INPUT_GAIN_MAX];
+
+	private->autogain_updated = 0;
+
+	if (!info->gain_input_count)
+		return 0;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_AUTOGAIN_SWITCH,
+		info->gain_input_count, private->autogain_switch);
+	if (err < 0)
+		return err;
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_AUTOGAIN_STATUS,
+		info->gain_input_count, raw_autogain_status);
+	if (err < 0)
+		return err;
+
+	/* Translate autogain_switch and raw_autogain_status into
+	 * autogain_status
+	 */
+	for (i = 0; i < info->gain_input_count; i++)
+		if (private->autogain_switch[i])
+			private->autogain_status[i] =
+				SCARLETT2_AUTOGAIN_STATUS_RUNNING;
+		else if (raw_autogain_status[i] == 0)
+			private->autogain_status[i] =
+				SCARLETT2_AUTOGAIN_STATUS_STOPPED;
+		else if (raw_autogain_status[i] >= 2 &&
+			 raw_autogain_status[i] <= 5)
+			private->autogain_status[i] =
+				SCARLETT2_AUTOGAIN_STATUS_FAILED;
+		else if (raw_autogain_status[i] == 6)
+			private->autogain_status[i] =
+				SCARLETT2_AUTOGAIN_STATUS_CANCELLED;
+		else
+			private->autogain_status[i] =
+				SCARLETT2_AUTOGAIN_STATUS_UNKNOWN;
+
+	return 0;
+}
+
+static int scarlett2_autogain_switch_ctl_get(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->autogain_updated) {
+		err = scarlett2_update_autogain(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] =
+		private->autogain_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_autogain_status_ctl_get(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->autogain_updated) {
+		err = scarlett2_update_autogain(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] =
+		private->autogain_status[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_autogain_switch_ctl_put(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int index = elem->control;
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	oval = private->autogain_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->autogain_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_AUTOGAIN_SWITCH, index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_autogain_status_ctl_info(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[SCARLETT2_AUTOGAIN_STATUS_COUNT] = {
+		"Stopped", "Running", "Failed", "Cancelled", "Unknown"
+	};
+
+	return snd_ctl_enum_info(
+		uinfo, 1, SCARLETT2_AUTOGAIN_STATUS_COUNT, values);
+}
+
+static const struct snd_kcontrol_new scarlett2_autogain_switch_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_autogain_switch_ctl_get,
+	.put  = scarlett2_autogain_switch_ctl_put
+};
+
+static const struct snd_kcontrol_new scarlett2_autogain_status_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.name = "",
+	.info = scarlett2_autogain_status_ctl_info,
+	.get  = scarlett2_autogain_status_ctl_get,
+};
+
+/*** Input Select Control ***/
+
+static int scarlett2_update_input_select(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int link_count = info->gain_input_count / 2;
+	int err;
+
+	private->input_select_updated = 0;
+
+	if (!link_count)
+		return 0;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_INPUT_SELECT_SWITCH,
+		1, &private->input_select_switch);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_INPUT_LINK_SWITCH,
+		link_count, private->input_link_switch);
+	if (err < 0)
+		return err;
+
+	/* simplified because no model yet has link_count > 1 */
+	if (private->input_link_switch[0])
+		private->input_select_switch = 0;
+
+	return 0;
+}
+
+static int scarlett2_input_select_ctl_get(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->input_select_updated) {
+		err = scarlett2_update_input_select(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->input_select_switch;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_input_select_ctl_put(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int oval, val, err = 0;
+	int max_val = private->input_link_switch[0] ? 0 : 1;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	oval = private->input_select_switch;
+	val = ucontrol->value.integer.value[0];
+
+	if (val < 0)
+		val = 0;
+	else if (val > max_val)
+		val = max_val;
+
+	if (oval == val)
+		goto unlock;
+
+	private->input_select_switch = val;
+
+	/* Send switch change to the device if inputs not linked */
+	if (!private->input_link_switch[0])
+		err = scarlett2_usb_set_config(
+			mixer, SCARLETT2_CONFIG_INPUT_SELECT_SWITCH,
+			1, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_input_select_ctl_info(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int inputs = private->info->gain_input_count;
+	int i, j;
+	int err;
+	char **values = kcalloc(inputs, sizeof(char *), GFP_KERNEL);
+
+	if (!values)
+		return -ENOMEM;
+
+	mutex_lock(&private->data_mutex);
+
+	/* Loop through each input
+	 * Linked inputs have one value for the pair
+	 */
+	for (i = 0, j = 0; i < inputs; i++) {
+		if (private->input_link_switch[i / 2]) {
+			values[j++] = kasprintf(
+				GFP_KERNEL, "Input %d-%d", i + 1, i + 2);
+			i++;
+		} else {
+			values[j++] = kasprintf(
+				GFP_KERNEL, "Input %d", i + 1);
+		}
+	}
+
+	err = snd_ctl_enum_info(uinfo, 1, j,
+				(const char * const *)values);
+
+	mutex_unlock(&private->data_mutex);
+
+	for (i = 0; i < inputs; i++)
+		kfree(values[i]);
+	kfree(values);
+
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_input_select_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_input_select_ctl_info,
+	.get  = scarlett2_input_select_ctl_get,
+	.put  = scarlett2_input_select_ctl_put,
+};
+
+/*** Input Link Switch Controls ***/
+
+static int scarlett2_input_link_ctl_get(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->input_select_updated) {
+		err = scarlett2_update_input_select(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] =
+		private->input_link_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_input_link_ctl_put(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int index = elem->control;
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	oval = private->input_link_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->input_link_switch[index] = val;
+
+	/* Notify of change in input select options available */
+	snd_ctl_notify(mixer->chip->card,
+		       SNDRV_CTL_EVENT_MASK_VALUE | SNDRV_CTL_EVENT_MASK_INFO,
+		       &private->input_select_ctl->id);
+	private->input_select_updated = 1;
+
+	/* Send switch change to the device
+	 * Link for channels 1-2 is at index 1
+	 * No device yet has more than 2 channels linked
+	 */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_INPUT_LINK_SWITCH, index + 1, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_input_link_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_input_link_ctl_get,
+	.put  = scarlett2_input_link_ctl_put
+};
+
+/*** Input Gain Controls ***/
+
+static int scarlett2_update_input_gain(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	private->input_gain_updated = 0;
+
+	if (!info->gain_input_count)
+		return 0;
+
+	return scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_INPUT_GAIN,
+		info->gain_input_count, private->gain);
+}
+
+static int scarlett2_input_gain_ctl_info(struct snd_kcontrol *kctl,
+					 struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = elem->channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = SCARLETT2_GAIN_BIAS;
+	uinfo->value.integer.step = 1;
+	return 0;
+}
+
+static int scarlett2_input_gain_ctl_get(struct snd_kcontrol *kctl,
+					struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->input_gain_updated) {
+		err = scarlett2_update_input_gain(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] =
+		private->gain[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_input_gain_ctl_put(struct snd_kcontrol *kctl,
+					struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int index = elem->control;
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	oval = private->gain[index];
+	val = ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->gain[index] = val;
+
+	/* Send gain change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_INPUT_GAIN,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const DECLARE_TLV_DB_MINMAX(
+	db_scale_scarlett2_gain, -SCARLETT2_GAIN_BIAS * 100, 0
+);
+
+static const struct snd_kcontrol_new scarlett2_input_gain_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
+		  SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+	.name = "",
+	.info = scarlett2_input_gain_ctl_info,
+	.get  = scarlett2_input_gain_ctl_get,
+	.put  = scarlett2_input_gain_ctl_put,
+	.private_value = 0, /* max value */
+	.tlv = { .p = db_scale_scarlett2_gain }
+};
+
+/*** Safe Controls ***/
+
+static int scarlett2_update_input_safe(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	private->input_safe_updated = 0;
+
+	if (!info->gain_input_count)
+		return 0;
+
+	return scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_SAFE_SWITCH,
+		info->gain_input_count, private->safe_switch);
+}
+
+static int scarlett2_safe_ctl_get(struct snd_kcontrol *kctl,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	if (private->input_safe_updated) {
+		err = scarlett2_update_input_safe(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] =
+		private->safe_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_safe_ctl_put(struct snd_kcontrol *kctl,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct usb_mixer_interface *mixer = elem->head.mixer;
+	struct scarlett2_data *private = mixer->private_data;
+
+	int index = elem->control;
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->hwdep_in_use) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	oval = private->safe_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->safe_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_SAFE_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_safe_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_safe_ctl_get,
+	.put  = scarlett2_safe_ctl_put,
+};
+
 /*** Analogue Line Out Volume Controls ***/
 
 /* Update hardware volume controls after receiving notification that
@@ -3908,6 +4549,60 @@ static int scarlett2_add_line_in_ctls(struct usb_mixer_interface *mixer)
 			return err;
 	}
 
+	/* Add software-controllable input gain controls */
+	if (info->gain_input_count) {
+		err = scarlett2_add_new_ctl(
+			mixer, &scarlett2_input_select_ctl, 0, 1,
+			"Input Select Capture Enum",
+			&private->input_select_ctl);
+		if (err < 0)
+			return err;
+
+		for (i = 0; i < info->gain_input_count; i++) {
+			if (i % 2) {
+				snprintf(s, sizeof(s),
+					 "Line In %d-%d Link Capture Switch",
+					 i, i + 1);
+				err = scarlett2_add_new_ctl(
+					mixer, &scarlett2_input_link_ctl,
+					i / 2, 1, s,
+					&private->input_link_ctls[i / 2]);
+				if (err < 0)
+					return err;
+			}
+
+			snprintf(s, sizeof(s), fmt, i + 1,
+				 "Gain", "Volume");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_input_gain_ctl,
+				i, 1, s, &private->input_gain_ctls[i]);
+			if (err < 0)
+				return err;
+
+			snprintf(s, sizeof(s), fmt, i + 1,
+				 "Autogain", "Switch");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_autogain_switch_ctl,
+				i, 1, s, &private->autogain_ctls[i]);
+			if (err < 0)
+				return err;
+
+			snprintf(s, sizeof(s), fmt, i + 1,
+				 "Autogain Status", "Enum");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_autogain_status_ctl,
+				i, 1, s, &private->autogain_status_ctls[i]);
+
+			snprintf(s, sizeof(s), fmt, i + 1,
+				 "Safe", "Switch");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_safe_ctl,
+				i, 1, s, &private->safe_ctls[i]);
+			if (err < 0)
+				return err;
+		}
+	}
+
 	return 0;
 }
 
@@ -4838,6 +5533,22 @@ static int scarlett2_read_configs(struct usb_mixer_interface *mixer)
 	if (err < 0)
 		return err;
 
+	err = scarlett2_update_input_select(mixer);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_update_input_gain(mixer);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_update_autogain(mixer);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_update_input_safe(mixer);
+	if (err < 0)
+		return err;
+
 	for (i = 0; i < private->num_mix_out; i++) {
 		err = scarlett2_usb_get_mix(mixer, i);
 		if (err < 0)
@@ -4970,6 +5681,89 @@ static void scarlett2_notify_input_other(struct usb_mixer_interface *mixer)
 	scarlett2_notify_input_phantom(mixer);
 }
 
+/* Notify on input select change */
+static __always_unused void scarlett2_notify_input_select(
+	struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int i;
+
+	if (!info->gain_input_count)
+		return;
+
+	private->input_select_updated = 1;
+
+	snd_ctl_notify(card,
+		       SNDRV_CTL_EVENT_MASK_VALUE | SNDRV_CTL_EVENT_MASK_INFO,
+		       &private->input_select_ctl->id);
+
+	for (i = 0; i < info->gain_input_count / 2; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->input_link_ctls[i]->id);
+}
+
+/* Notify on input gain change */
+static __always_unused void scarlett2_notify_input_gain(
+	struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int i;
+
+	if (!info->gain_input_count)
+		return;
+
+	private->input_gain_updated = 1;
+
+	for (i = 0; i < info->gain_input_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->input_gain_ctls[i]->id);
+}
+
+/* Notify on autogain change */
+static __always_unused void scarlett2_notify_autogain(
+	struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int i;
+
+	if (!info->gain_input_count)
+		return;
+
+	private->autogain_updated = 1;
+
+	for (i = 0; i < info->gain_input_count; i++) {
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->autogain_ctls[i]->id);
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->autogain_status_ctls[i]->id);
+	}
+}
+
+/* Notify on input safe switch change */
+static __always_unused void scarlett2_notify_input_safe(
+	struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int i;
+
+	if (!info->gain_input_count)
+		return;
+
+	private->input_safe_updated = 1;
+
+	for (i = 0; i < info->gain_input_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->safe_ctls[i]->id);
+}
+
 /* Notify on "monitor other" change (speaker switching, talkback) */
 static void scarlett2_notify_monitor_other(struct usb_mixer_interface *mixer)
 {