[PATCH v2] ALSA: scarlett2: Fix Scarlett 4th Gen input gain range

["Geoffrey D. Bennett" <g@xxxxx>]

The input gain range TLV was previously declared as -70dB to 0dB, but
the preamp gain range is 0dB to +69dB, set with values ranging from 0 to
70. Replace SCARLETT2_GAIN_BIAS with SCARLETT2_MAX_GAIN_VALUE and
SCARLETT2_MAX_GAIN_DB, and update the TLV.

Signed-off-by: Geoffrey D. Bennett <g@xxxxx>
Fixes: 0a995e38dc44 ("ALSA: scarlett2: Add support for software-controllable input gain")
---
 sound/usb/mixer_scarlett2.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/sound/usb/mixer_scarlett2.c b/sound/usb/mixer_scarlett2.c
index 3815ce1d216e..bd114be537d7 100644
--- a/sound/usb/mixer_scarlett2.c
+++ b/sound/usb/mixer_scarlett2.c
@@ -173,7 +173,12 @@
 
 /* some gui mixers can't handle negative ctl values */
 #define SCARLETT2_VOLUME_BIAS 127
-#define SCARLETT2_GAIN_BIAS 70
+
+/* maximum preamp input gain and value
+ * values are from 0 to 70, preamp gain is from 0 to 69dB
+ */
+#define SCARLETT2_MAX_GAIN_VALUE 70
+#define SCARLETT2_MAX_GAIN_DB 69
 
 /* mixer range from -80dB to +6dB in 0.5dB steps */
 #define SCARLETT2_MIXER_MIN_DB -80
@@ -3464,7 +3469,7 @@ static int scarlett2_input_gain_ctl_info(struct snd_kcontrol *kctl,
 	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.max = SCARLETT2_MAX_GAIN_VALUE;
 	uinfo->value.integer.step = 1;
 
 unlock:
@@ -3541,7 +3546,7 @@ static int scarlett2_input_gain_ctl_put(struct snd_kcontrol *kctl,
 }
 
 static const DECLARE_TLV_DB_MINMAX(
-	db_scale_scarlett2_gain, -SCARLETT2_GAIN_BIAS * 100, 0
+	db_scale_scarlett2_gain, 0, SCARLETT2_MAX_GAIN_DB * 100
 );
 
 static const struct snd_kcontrol_new scarlett2_input_gain_ctl = {
-- 
2.43.0