[alsa-devel] [PATCH 2/2] [RFC] ALSA: hda: hdmi - preserve non-MST PCM routing for Intel platforms

[Kai Vehmanen]

Commit 5398e94fb753 ("ALSA: hda - Add DP-MST support for NVIDIA codecs")
introduced a slight change of behaviour how non-MST monitors are
assigned to PCMs on Intel platforms.

In the drm_audio_component.h interface, the third parameter
to pin_eld_notify() is pipe number. On Intel platforms, this value
is -1 for MST. On other platforms, a non-zero pipe id is used to
signal MST use.

This difference leads to some subtle differences in hdmi_find_pcm_slot()
with regards to how non-MST monitors are assigned to PCMs.
This patch restores the original behaviour on Intel platforms while
keeping the new allocation policy on other platforms.

Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>
---
 sound/pci/hda/patch_hdmi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index c3940c197122..1dd4c92254a4 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -1353,6 +1353,11 @@ static int hdmi_find_pcm_slot(struct hdmi_spec *spec,
 		i = spec->num_nids + (per_pin->dev_id - 1);
 		if (i < spec->pcm_used && !(test_bit(i, &spec->pcm_bitmap)))
 			return i;
+
+		/* keep legacy assignment for dev_id>0 on Intel platforms */
+		if (spec->intel_hsw_fixup)
+			if (!test_bit(per_pin->pin_nid_idx, &spec->pcm_bitmap))
+				return per_pin->pin_nid_idx;
 	}
 
 	/* have a second try; check the area over num_nids */
-- 
2.17.1