usb6fire_control_input_vol_put() stores the analog capture volume
as a signed offset in rt->input_vol[] (-15..+15), but it compares
the cached value against the user-visible mixer value (0..30)
before subtracting 15.

This mixes two domains in the change detection path. Since the
runtime is zero-initialized, the visible default is 15; writing 0
right after probe is ignored, while writing 15 is reported as a
change even though the cached value remains 0.

Normalize the user value before comparing it with the cached offset.

Fixes: 06bb4e743501 ("ALSA: snd-usb-6fire: add analog input volume control")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/6fire/control.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/sound/usb/6fire/control.c b/sound/usb/6fire/control.c
index dd25a6407b63..c77a21a9acd7 100644
--- a/sound/usb/6fire/control.c
+++ b/sound/usb/6fire/control.c
@@ -290,15 +290,17 @@ static int usb6fire_control_input_vol_put(struct snd_kcontrol *kcontrol,
 		struct snd_ctl_elem_value *ucontrol)
 {
 	struct control_runtime *rt = snd_kcontrol_chip(kcontrol);
+	int vol0 = ucontrol->value.integer.value[0] - 15;
+	int vol1 = ucontrol->value.integer.value[1] - 15;
 	int changed = 0;
 
-	if (rt->input_vol[0] != ucontrol->value.integer.value[0]) {
-		rt->input_vol[0] = ucontrol->value.integer.value[0] - 15;
+	if (rt->input_vol[0] != vol0) {
+		rt->input_vol[0] = vol0;
 		rt->ivol_updated &= ~(1 << 0);
 		changed = 1;
 	}
-	if (rt->input_vol[1] != ucontrol->value.integer.value[1]) {
-		rt->input_vol[1] = ucontrol->value.integer.value[1] - 15;
+	if (rt->input_vol[1] != vol1) {
+		rt->input_vol[1] = vol1;
 		rt->ivol_updated &= ~(1 << 1);
 		changed = 1;
 	}

---
base-commit: 10cdf5ba267d89b7fc5d9f693c65a6e4af3f8e13
change-id: 20260416-alsa-6fire-input-volume-change-detection-de50b8fe278f

Best regards,
--  
Cássio Gabriel <cassiogabrielcontato@gmail.com>

On Thu, 16 Apr 2026 15:24:40 +0200,
Cássio Gabriel wrote:
> 
> usb6fire_control_input_vol_put() stores the analog capture volume
> as a signed offset in rt->input_vol[] (-15..+15), but it compares
> the cached value against the user-visible mixer value (0..30)
> before subtracting 15.
> 
> This mixes two domains in the change detection path. Since the
> runtime is zero-initialized, the visible default is 15; writing 0
> right after probe is ignored, while writing 15 is reported as a
> change even though the cached value remains 0.
> 
> Normalize the user value before comparing it with the cached offset.
> 
> Fixes: 06bb4e743501 ("ALSA: snd-usb-6fire: add analog input volume control")
> Cc: stable@vger.kernel.org
> Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>

Thanks, applied now.


Takashi