ALSA: usb-audio: Add input gain and master output mixer elements for RME Babyface Pro

Add missing input gain and master output mixer controls for
RME Babyface Pro.

This patch implements:

1. Input gain controls for 2 mic and 2 line inputs
2. Master output volume controls for all 12 output channels

These additions allow for more complete control of the Babyface Pro under
Linux.

Signed-off-by: Stefan Stistrup <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

sound/usb/mixer_quirks.c

···
 #define SND_BBFPRO_CTL_REG2_PAD_AN1 4
 #define SND_BBFPRO_CTL_REG2_PAD_AN2 5
 
-#define SND_BBFPRO_MIXER_IDX_MASK 0x1ff
+#define SND_BBFPRO_MIXER_MAIN_OUT_CH_OFFSET 992
+#define SND_BBFPRO_MIXER_IDX_MASK 0x3ff
 #define SND_BBFPRO_MIXER_VAL_MASK 0x3ffff
 #define SND_BBFPRO_MIXER_VAL_SHIFT 9
 #define SND_BBFPRO_MIXER_VAL_MIN 0 // -inf
 #define SND_BBFPRO_MIXER_VAL_MAX 65536 // +6dB
 
+#define SND_BBFPRO_GAIN_CHANNEL_MASK 0x03
+#define SND_BBFPRO_GAIN_CHANNEL_SHIFT 7
+#define SND_BBFPRO_GAIN_VAL_MASK 0x7f
+#define SND_BBFPRO_GAIN_VAL_MIN 0
+#define SND_BBFPRO_GAIN_VAL_MIC_MAX 65
+#define SND_BBFPRO_GAIN_VAL_LINE_MAX 18 // 9db in 0.5db incraments
+
 #define SND_BBFPRO_USBREQ_CTL_REG1 0x10
 #define SND_BBFPRO_USBREQ_CTL_REG2 0x17
+#define SND_BBFPRO_USBREQ_GAIN 0x1a
 #define SND_BBFPRO_USBREQ_MIXER 0x12
 
 static int snd_bbfpro_ctl_update(struct usb_mixer_interface *mixer, u8 reg,
···
 	return snd_bbfpro_ctl_update(list->mixer, reg, idx, value);
 }
 
+static int snd_bbfpro_gain_update(struct usb_mixer_interface *mixer,
+				  u8 channel, u8 gain)
+{
+	int err;
+	struct snd_usb_audio *chip = mixer->chip;
+
+	if (channel < 2) {
+		// XLR preamp: 3-bit fine, 5-bit coarse; special case >60
+		if (gain < 60)
+			gain = ((gain % 3) << 5) | (gain / 3);
+		else
+			gain = ((gain % 6) << 5) | (60 / 3);
+	}
+
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+
+	err = snd_usb_ctl_msg(chip->dev,
+			      usb_sndctrlpipe(chip->dev, 0),
+			      SND_BBFPRO_USBREQ_GAIN,
+			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+			      gain, channel, NULL, 0);
+
+	snd_usb_unlock_shutdown(chip);
+	return err;
+}
+
+static int snd_bbfpro_gain_get(struct snd_kcontrol *kcontrol,
+			       struct snd_ctl_elem_value *ucontrol)
+{
+	int value = kcontrol->private_value & SND_BBFPRO_GAIN_VAL_MASK;
+
+	ucontrol->value.integer.value[0] = value;
+	return 0;
+}
+
+static int snd_bbfpro_gain_info(struct snd_kcontrol *kcontrol,
+				struct snd_ctl_elem_info *uinfo)
+{
+	int pv, channel;
+
+	pv = kcontrol->private_value;
+	channel = (pv >> SND_BBFPRO_GAIN_CHANNEL_SHIFT) &
+		SND_BBFPRO_GAIN_CHANNEL_MASK;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 1;
+	uinfo->value.integer.min = SND_BBFPRO_GAIN_VAL_MIN;
+
+	if (channel < 2)
+		uinfo->value.integer.max = SND_BBFPRO_GAIN_VAL_MIC_MAX;
+	else
+		uinfo->value.integer.max = SND_BBFPRO_GAIN_VAL_LINE_MAX;
+
+	return 0;
+}
+
+static int snd_bbfpro_gain_put(struct snd_kcontrol *kcontrol,
+			       struct snd_ctl_elem_value *ucontrol)
+{
+	int pv, channel, old_value, value, err;
+
+	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kcontrol);
+	struct usb_mixer_interface *mixer = list->mixer;
+
+	pv = kcontrol->private_value;
+	channel = (pv >> SND_BBFPRO_GAIN_CHANNEL_SHIFT) &
+		SND_BBFPRO_GAIN_CHANNEL_MASK;
+	old_value = pv & SND_BBFPRO_GAIN_VAL_MASK;
+	value = ucontrol->value.integer.value[0];
+
+	if (value < SND_BBFPRO_GAIN_VAL_MIN)
+		return -EINVAL;
+
+	if (channel < 2) {
+		if (value > SND_BBFPRO_GAIN_VAL_MIC_MAX)
+			return -EINVAL;
+	} else {
+		if (value > SND_BBFPRO_GAIN_VAL_LINE_MAX)
+			return -EINVAL;
+	}
+
+	if (value == old_value)
+		return 0;
+
+	err = snd_bbfpro_gain_update(mixer, channel, value);
+	if (err < 0)
+		return err;
+
+	kcontrol->private_value =
+		(channel << SND_BBFPRO_GAIN_CHANNEL_SHIFT) | value;
+	return 1;
+}
+
+static int snd_bbfpro_gain_resume(struct usb_mixer_elem_list *list)
+{
+	int pv, channel, value;
+	struct snd_kcontrol *kctl = list->kctl;
+
+	pv = kctl->private_value;
+	channel = (pv >> SND_BBFPRO_GAIN_CHANNEL_SHIFT) &
+		SND_BBFPRO_GAIN_CHANNEL_MASK;
+	value = pv & SND_BBFPRO_GAIN_VAL_MASK;
+
+	return snd_bbfpro_gain_update(list->mixer, channel, value);
+}
+
 static int snd_bbfpro_vol_update(struct usb_mixer_interface *mixer, u16 index,
 				 u32 value)
 {
···
 	.put = snd_bbfpro_ctl_put
 };
 
+static const struct snd_kcontrol_new snd_bbfpro_gain_control = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+	.index = 0,
+	.info = snd_bbfpro_gain_info,
+	.get = snd_bbfpro_gain_get,
+	.put = snd_bbfpro_gain_put
+};
+
 static const struct snd_kcontrol_new snd_bbfpro_vol_control = {
 	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
 	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
···
 			<< SND_BBFPRO_CTL_IDX_SHIFT);
 
 	return add_single_ctl_with_resume(mixer, 0, snd_bbfpro_ctl_resume,
+		&knew, NULL);
+}
+
+static int snd_bbfpro_gain_add(struct usb_mixer_interface *mixer, u8 channel,
+			       char *name)
+{
+	struct snd_kcontrol_new knew = snd_bbfpro_gain_control;
+
+	knew.name = name;
+	knew.private_value = channel << SND_BBFPRO_GAIN_CHANNEL_SHIFT;
+
+	return add_single_ctl_with_resume(mixer, 0, snd_bbfpro_gain_resume,
 		&knew, NULL);
 }
 
···
 			if (err < 0)
 				return err;
 		}
+	}
+
+	// Main out volume
+	for (i = 0 ; i < 12 ; ++i) {
+		snprintf(name, sizeof(name), "Main-Out %s", output[i]);
+		// Main outs are offset to 992
+		err = snd_bbfpro_vol_add(mixer,
+					 i + SND_BBFPRO_MIXER_MAIN_OUT_CH_OFFSET,
+					 name);
+		if (err < 0)
+			return err;
+	}
+
+	// Input gain
+	for (i = 0 ; i < 4 ; ++i) {
+		if (i < 2)
+			snprintf(name, sizeof(name), "Mic-%s Gain", input[i]);
+		else
+			snprintf(name, sizeof(name), "Line-%s Gain", input[i]);
+
+		err = snd_bbfpro_gain_add(mixer, i, name);
+		if (err < 0)
+			return err;
 	}
 
 	// Control Reg 1