ALSA: hda - use both input paths on Conexant auto parser

On the Thinkpad W520 - and probably several other machines with
Conexant 506x chips - the Dock Mic and Mic are connected to the
same two selector nodes. This patch will make Dock Mic take one
selector node and Mic take the other, when possible.

Without the patch, both paths would take the first selector,
leading to the normal Mic's volume being controlled by
"Dock Mic Boost".
(On other machines, this could instead fixup similar problems between
Mic and Line In, for example.)

BugLink: https://bugs.launchpad.net/bugs/1037642
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_conexant.c

@@ -3540,8 +3540,9 @@ static int __select_input_connection(struct hda_codec *codec, hda_nid_t mux,
 				     hda_nid_t pin, hda_nid_t *srcp,
 				     bool do_select, int depth)
 {
+	struct conexant_spec *spec = codec->spec;
 	hda_nid_t conn[HDA_MAX_NUM_INPUTS];
-	int i, nums;
+	int startidx, i, nums;
 
 	switch (get_wcaps_type(get_wcaps(codec, mux))) {
 	case AC_WID_AUD_IN:
@@ -3565,14 +3566,25 @@ static int __select_input_connection(struct hda_codec *codec, hda_nid_t mux,
 	depth++;
 	if (depth == 2)
 		return -1;
+
+	/* Try to rotate around connections to avoid one boost controlling
+	   another input path as well */
+	startidx = 0;
+	for (i = 0; i < spec->private_imux.num_items; i++)
+		if (spec->imux_info[i].pin == pin) {
+			startidx = i;
+			break;
+		}
+
 	for (i = 0; i < nums; i++) {
-		int ret  = __select_input_connection(codec, conn[i], pin, srcp,
+		int j = (i + startidx) % nums;
+		int ret  = __select_input_connection(codec, conn[j], pin, srcp,
 						     do_select, depth);
 		if (ret >= 0) {
 			if (do_select)
 				snd_hda_codec_write(codec, mux, 0,
-						    AC_VERB_SET_CONNECT_SEL, i);
-			return i;
+						    AC_VERB_SET_CONNECT_SEL, j);
+			return j;
 		}
 	}
 	return -1;