[PATCH] ASoC: hdmi-codec: Report a change when the channel status moves

[HyeongJun An]

The put() callback of "IEC958 Playback Default" stores all 24 channel
status bytes and then returns 0. The core notifies userspace only on a
positive return, so a write that changes what the get() callback hands
back is never announced, and a mixer holding the control open keeps
showing the old value.

Compare the stored bytes and return 1 when they move, the way
snd_hda_spdif_default_put() does.

The same shape is in img-spdif-out and uniperif_player.

No board with this codec was to hand. The change is a comparison of
driver state with no hardware behaviour in it, and mixer-test counts the
missing notification as event_missing.

Fixes: 7a8e1d44211e ("ASoC: hdmi-codec: Add iec958 controls")
Signed-off-by: HyeongJun An <sammiee5311@xxxxxxxxx>
Assisted-by: Claude:claude-opus-5
---
 sound/soc/codecs/hdmi-codec.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/hdmi-codec.c b/sound/soc/codecs/hdmi-codec.c
index bc2c22436ba6..7aa50c5bd3df 100644
--- a/sound/soc/codecs/hdmi-codec.c
+++ b/sound/soc/codecs/hdmi-codec.c
@@ -426,10 +426,14 @@ static int hdmi_codec_iec958_default_put(struct snd_kcontrol *kcontrol,
 	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
 	struct hdmi_codec_priv *hcp = snd_soc_component_get_drvdata(component);
 
+	if (!memcmp(hcp->iec_status, ucontrol->value.iec958.status,
+		    sizeof(hcp->iec_status)))
+		return 0;
+
 	memcpy(hcp->iec_status, ucontrol->value.iec958.status,
 	       sizeof(hcp->iec_status));
 
-	return 0;
+	return 1;
 }
 
 static int hdmi_codec_iec958_mask_get(struct snd_kcontrol *kcontrol,
-- 
2.43.0