ALSA: hda - Don't register a cb func if it is registered already

If the caller of enable_callback_mst() passes a cb func, the callee
function will malloc memory and link this cb func to the list
unconditionally. This will introduce problem if caller is in the
hda_codec_ops.init() since the init() will be repeatedly called in the
codec rt_resume().

So far, the patch_hdmi.c and patch_ca0132.c call enable_callback_mst()
in the hda_codec_ops.init().
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200930055146.5665-1-hui.wang@canonical.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_jack.c

@@ -275,6 +275,18 @@ int snd_hda_jack_detect_state_mst(struct hda_codec *codec,
 }
 EXPORT_SYMBOL_GPL(snd_hda_jack_detect_state_mst);
 
+static bool func_is_already_in_callback_list(struct hda_jack_tbl *jack,
+					     hda_jack_callback_fn func)
+{
+	struct hda_jack_callback *cb;
+
+	for (cb = jack->callback; cb; cb = cb->next) {
+		if (cb->func == func)
+			return true;
+	}
+	return false;
+}
+
 /**
  * snd_hda_jack_detect_enable_mst - enable the jack-detection
  * @codec: the HDA codec
@@ -297,7 +309,7 @@ snd_hda_jack_detect_enable_callback_mst(struct hda_codec *codec, hda_nid_t nid,
 	jack = snd_hda_jack_tbl_new(codec, nid, dev_id);
 	if (!jack)
 		return ERR_PTR(-ENOMEM);
-	if (func) {
+	if (func && !func_is_already_in_callback_list(jack, func)) {
 		callback = kzalloc(sizeof(*callback), GFP_KERNEL);
 		if (!callback)
 			return ERR_PTR(-ENOMEM);