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From 8ccfffa0584532d9a98646bc39ead0e2361a86a2 Mon Sep 17 00:00:00 2001
From: Anssi Hannula <anssi.hannula@iki.fi>
Date: Sun, 16 Aug 2015 15:50:12 +0300
Subject: [PATCH 1/3] ALSA: usb-audio: Add a volume scale quirk for AudioQuest
DragonFly
AudioQuest DragonFly DAC reports a volume control range of 0..50
(0x0000..0x0032) which in USB Audio means a range of 0 .. 0.2dB, which
is obviously incorrect and causes software using the dB information in
e.g. volume sliders to have a massive volume difference in 100..102%
range.
The actual volume mapping seems to be neither linear volume nor linear
dB scale, but instead quite close to the cubic mapping e.g. alsamixer
uses, with a range of -53...0 dB.
Add a quirk for DragonFly to use a custom dB mapping, based on my
measurements, using a 10-item range TLV (so it still fits in alsa-lib
MAX_TLV_RANGE_SIZE).
Tested on AudioQuest DragonFly HW v1.2. The quirk is only applied if the
range is 0..50, so if this gets fixed/changed in later HW revisions it
will no longer be applied.
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Cc: <stable@vger.kernel.org>
---
sound/usb/mixer_quirks.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index d3608c0..dee73fa 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -37,6 +37,7 @@
#include <sound/control.h>
#include <sound/hwdep.h>
#include <sound/info.h>
+#include <sound/tlv.h>
#include "usbaudio.h"
#include "mixer.h"
@@ -1715,6 +1716,38 @@ static int snd_microii_controls_create(struct usb_mixer_interface *mixer)
return 0;
}
+static void snd_dragonfly_quirk_db_scale(struct usb_mixer_interface *mixer)
+{
+ struct usb_mixer_elem_list *list;
+ struct usb_mixer_elem_info *cval;
+ static const int unit_id = 7;
+
+ /* approximation using 10 ranges based on output measurement on hw v1.2 */
+ static const DECLARE_TLV_DB_RANGE(scale,
+ 0, 1, TLV_DB_MINMAX_ITEM(-5300, -4970),
+ 2, 5, TLV_DB_MINMAX_ITEM(-4710, -4160),
+ 6, 7, TLV_DB_MINMAX_ITEM(-3884, -3710),
+ 8, 14, TLV_DB_MINMAX_ITEM(-3443, -2560),
+ 15, 16, TLV_DB_MINMAX_ITEM(-2475, -2324),
+ 17, 19, TLV_DB_MINMAX_ITEM(-2228, -2031),
+ 20, 26, TLV_DB_MINMAX_ITEM(-1910, -1393),
+ 27, 31, TLV_DB_MINMAX_ITEM(-1322, -1032),
+ 32, 40, TLV_DB_MINMAX_ITEM(-968, -490),
+ 41, 50, TLV_DB_MINMAX_ITEM(-441, 0),
+ );
+
+ for (list = mixer->id_elems[unit_id]; list; list = list->next_id_elem) {
+ cval = (struct usb_mixer_elem_info *)list;
+ if (cval->control == UAC_FU_VOLUME &&
+ cval->min == 0 && cval->max == 50) {
+ usb_audio_info(mixer->chip, "applying DragonFly dB scale quirk\n");
+ list->kctl->tlv.p = scale;
+ list->kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
+ list->kctl->vd[0].access &= ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
+ }
+ }
+}
+
int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
{
int err = 0;
@@ -1792,6 +1825,10 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
case USB_ID(0x1235, 0x800c): /* Focusrite Scarlett 18i20 */
err = snd_scarlett_controls_create(mixer);
break;
+
+ case USB_ID(0x21b4, 0x0081): /* AudioQuest DragonFly */
+ snd_dragonfly_quirk_db_scale(mixer);
+ break;
}
return err;
--
2.5.3
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