[PATCH] ALSA: hda: Fix headset detection failure due to unstable sort

[Kuan-Wei Chiu <visitorckw@gmail.com>]

The auto_parser assumed sort() was stable, but the kernel's sort() uses
heapsort, which has never been stable. After commit 0e02ca29a563
("lib/sort: optimize heapsort with double-pop variation"), the order of
equal elements changed, causing the headset to fail to work.

Fix the issue by recording the original order of elements before
sorting and using it as a tiebreaker for equal elements in the
comparison function.

Fixes: b9030a005d58 ("ALSA: hda - Use standard sort function in hda_auto_parser.c")
Reported-by: Austrum <austrum.lab@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219158
Tested-by: Austrum <austrum.lab@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
 sound/pci/hda/hda_auto_parser.c | 8 +++++++-
 sound/pci/hda/hda_auto_parser.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/sound/pci/hda/hda_auto_parser.c b/sound/pci/hda/hda_auto_parser.c
index 84393f4f429d..8923813ce424 100644
--- a/sound/pci/hda/hda_auto_parser.c
+++ b/sound/pci/hda/hda_auto_parser.c
@@ -80,7 +80,11 @@ static int compare_input_type(const void *ap, const void *bp)
 
 	/* In case one has boost and the other one has not,
 	   pick the one with boost first. */
-	return (int)(b->has_boost_on_pin - a->has_boost_on_pin);
+	if (a->has_boost_on_pin != b->has_boost_on_pin)
+		return (int)(b->has_boost_on_pin - a->has_boost_on_pin);
+
+	/* Keep the original order */
+	return a->order - b->order;
 }
 
 /* Reorder the surround channels
@@ -400,6 +404,8 @@ int snd_hda_parse_pin_defcfg(struct hda_codec *codec,
 	reorder_outputs(cfg->speaker_outs, cfg->speaker_pins);
 
 	/* sort inputs in the order of AUTO_PIN_* type */
+	for (i = 0; i < cfg->num_inputs; i++)
+		cfg->inputs[i].order = i;
 	sort(cfg->inputs, cfg->num_inputs, sizeof(cfg->inputs[0]),
 	     compare_input_type, NULL);
 
diff --git a/sound/pci/hda/hda_auto_parser.h b/sound/pci/hda/hda_auto_parser.h
index 579b11beac71..87af3d8c02f7 100644
--- a/sound/pci/hda/hda_auto_parser.h
+++ b/sound/pci/hda/hda_auto_parser.h
@@ -37,6 +37,7 @@ struct auto_pin_cfg_item {
 	unsigned int is_headset_mic:1;
 	unsigned int is_headphone_mic:1; /* Mic-only in headphone jack */
 	unsigned int has_boost_on_pin:1;
+	int order;
 };
 
 struct auto_pin_cfg;
-- 
2.34.1