[alsa-devel] [PATCH] ALSA: hda - Do not wrongly restrict min_channels based on ELD

[Anssi Hannula]

Commit bbbe33900d1f3c added functionality to restrict PCM parameters
based on ELD info (derived from EDID data) of the audio sink.

However, it wrongly assumes that the bits 0-2 of the first byte of
CEA Short Audio Descriptors mean a supported number of channels. In
reality, they mean the maximum number of channels (as per CEA-861-D
7.5.2). This means that the channel count can only be used to restrict
max_channels, not min_channels.

Restricting min_channels causes us to deny opening the device in stereo
mode if the sink only has SADs that declare larger numbers of channels
(like Primare SP32 AV Processor does).

Fix that by not restricting min_channels based on ELD information.

Signed-off-by: Anssi Hannula <anssi.hannula at iki.fi>
Reported-by: Jean-Yves Avenard <jyavenard at gmail.com>
Tested-by: Jean-Yves Avenard <jyavenard at gmail.com>
Cc: stable at kernel.org
---

I think this should go to 2.6.36 stable tree as well. It does not affect
earlier stable releases.

 sound/pci/hda/hda_eld.c    |    4 ----
 sound/pci/hda/patch_hdmi.c |    1 -
 2 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c
index cb0c23a..47ef8aa 100644
--- a/sound/pci/hda/hda_eld.c
+++ b/sound/pci/hda/hda_eld.c
@@ -601,13 +601,10 @@ void hdmi_eld_update_pcm_info(struct hdmi_eld *eld, struct hda_pcm_stream *pcm,
 	pcm->rates = 0;
 	pcm->formats = 0;
 	pcm->maxbps = 0;
-	pcm->channels_min = -1;
 	pcm->channels_max = 0;
 	for (i = 0; i < eld->sad_count; i++) {
 		struct cea_sad *a = &eld->sad[i];
 		pcm->rates |= a->rates;
-		if (a->channels < pcm->channels_min)
-			pcm->channels_min = a->channels;
 		if (a->channels > pcm->channels_max)
 			pcm->channels_max = a->channels;
 		if (a->format == AUDIO_CODING_TYPE_LPCM) {
@@ -635,7 +632,6 @@ void hdmi_eld_update_pcm_info(struct hdmi_eld *eld, struct hda_pcm_stream *pcm,
 	/* restrict the parameters by the values the codec provides */
 	pcm->rates &= codec_pars->rates;
 	pcm->formats &= codec_pars->formats;
-	pcm->channels_min = max(pcm->channels_min, codec_pars->channels_min);
 	pcm->channels_max = min(pcm->channels_max, codec_pars->channels_max);
 	pcm->maxbps = min(pcm->maxbps, codec_pars->maxbps);
 }
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index d3e49aa..31df774 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -834,7 +834,6 @@ static int hdmi_pcm_open(struct hda_pcm_stream *hinfo,
 			return -ENODEV;
 	} else {
 		/* fallback to the codec default */
-		hinfo->channels_min = codec_pars->channels_min;
 		hinfo->channels_max = codec_pars->channels_max;
 		hinfo->rates = codec_pars->rates;
 		hinfo->formats = codec_pars->formats;
-- 
1.7.3