[PATCH 4/4] ALSA: mixer_evo: Add tlv for mixer channels

[Christian Ruppert <arc@gmx.li>]

mixer_evo didn't declare tlv for the recording mixer matrix which seems to
confuse some userland programs. Add tlv definitions to fix this.

We still do not add tlv for the crossfader (generally labelled "mixer")
because there doesn't seem to be a way to declare this so that userland
programs just keep it as linear as it is and should be.

Signed-off-by: Christian Ruppert <arc@gmx.li>
---
 sound/usb/mixer_evo.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/sound/usb/mixer_evo.c b/sound/usb/mixer_evo.c
index 867d083953ba..c1e0332232f2 100644
--- a/sound/usb/mixer_evo.c
+++ b/sound/usb/mixer_evo.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <sound/core.h>
 #include <sound/control.h>
+#include <sound/tlv.h>
 
 #include "usbaudio.h"
 #include "mixer.h"
@@ -31,6 +32,9 @@ enum snd_evo_type {
 	SND_EVO_TYPE_NCTYPES
 };
 
+/* Mixer matrix: -128dB (mute) to +6dB */
+static const DECLARE_TLV_DB_MINMAX_MUTE(snd_evo_tlv_mixer, -12800, 600);
+
 static const struct snd_evo_ctrl_type {
 	snd_ctl_elem_type_t type;
 	bool invert;
@@ -40,6 +44,7 @@ static const struct snd_evo_ctrl_type {
 	union {
 		int integer;
 	} max;
+	const unsigned int *tlv;
 	u16 wValue;
 	u16 wIndex;
 } snd_evo_ctypes[SND_EVO_TYPE_NCTYPES] = {
@@ -49,6 +54,7 @@ static const struct snd_evo_ctrl_type {
 		.max.integer = 127,
 		.wValue = 0x0000,
 		.wIndex = 0x3800,
+		/* no TLV here because we can't describe the cross-fader */
 	},
 	[SND_EVO_TYPE_PHANTOM] = {
 		.type = SNDRV_CTL_ELEM_TYPE_BOOLEAN,
@@ -80,6 +86,7 @@ static const struct snd_evo_ctrl_type {
 		.max.integer = 6 * 256,
 		.wValue = 0x0100,
 		.wIndex = 0x3C00,
+		.tlv = snd_evo_tlv_mixer,
 	},
 };
 
@@ -431,8 +438,6 @@ static int snd_ctl_evo_info(struct snd_kcontrol *kctl,
 	const struct snd_evo_ctrl_type *const ctype = snd_evo_kctl_type(kctl);
 
 	uinfo->type = ctype->type;
-	uinfo->access = SNDRV_CTL_ELEM_ACCESS_READWRITE
-			| SNDRV_CTL_ELEM_ACCESS_VOLATILE;
 	uinfo->count = snd_evo_kctl_channels(kctl);
 	uinfo->value.integer.min = ctype->min.integer;
 	uinfo->value.integer.max = ctype->max.integer;
@@ -454,6 +459,10 @@ static int snd_evo_add_ctrl(struct usb_mixer_interface *mixer,
 	knew.info = snd_ctl_evo_info;
 	knew.private_value = snd_evo_kctl_priv(ctrl->type, ctrl->val_offs,
 					       ctrl->hwchannels);
+	knew.tlv.p = ctype->tlv;
+	knew.access = SNDRV_CTL_ELEM_ACCESS_READWRITE
+			| SNDRV_CTL_ELEM_ACCESS_VOLATILE
+			| (ctype->tlv ? SNDRV_CTL_ELEM_ACCESS_TLV_READ : 0);
 
 	switch (ctype->type) {
 	case SNDRV_CTL_ELEM_TYPE_INTEGER:
-- 
2.56.0