[alsa-devel] [PATCH v4] ALSA: hdmi: expose ELD control

[Pierre-Louis Bossart]

Applications may want to read ELD information to
understand what codecs are supported on the HDMI
receiver and handle the a-v delay for better lip-sync.

ELD information is exposed in a device-specific
IFACE_PCM kcontrol. Tested both with amixer and
PulseAudio; with a corresponding patch passthrough modes
are enabled automagically.

ELD control size is set to zero in case of errors or
wrong configurations. No notifications are implemented
for now, it is expected that jack detection is used to
reconfigure the audio outputs.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 sound/pci/hda/hda_eld.c    |   13 +++++---
 sound/pci/hda/hda_local.h  |    2 +
 sound/pci/hda/patch_hdmi.c |   68 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 5 deletions(-)

diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c
index c34f730..f1c621d 100644
--- a/sound/pci/hda/hda_eld.c
+++ b/sound/pci/hda/hda_eld.c
@@ -318,6 +318,11 @@ int snd_hdmi_get_eld(struct hdmi_eld *eld,
 	int size;
 	unsigned char *buf;
 
+	/*
+	 * ELD size is initialized to zero in caller function. If no errors and
+	 * ELD is valid, actual eld_size is assigned in hdmi_update_eld()
+	 */
+
 	if (!eld->eld_valid)
 		return -ENOENT;
 
@@ -327,14 +332,13 @@ int snd_hdmi_get_eld(struct hdmi_eld *eld,
 		snd_printd(KERN_INFO "HDMI: ELD buf size is 0, force 128\n");
 		size = 128;
 	}
-	if (size < ELD_FIXED_BYTES || size > PAGE_SIZE) {
+	if (size < ELD_FIXED_BYTES || size > ELD_MAX_SIZE) {
 		snd_printd(KERN_INFO "HDMI: invalid ELD buf size %d\n", size);
 		return -ERANGE;
 	}
 
-	buf = kmalloc(size, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
+	/* set ELD buffer */
+	buf = eld->eld_buffer;
 
 	for (i = 0; i < size; i++) {
 		unsigned int val = hdmi_get_eld_data(codec, nid, i);
@@ -356,7 +360,6 @@ int snd_hdmi_get_eld(struct hdmi_eld *eld,
 	ret = hdmi_update_eld(eld, buf, size);
 
 error:
-	kfree(buf);
 	return ret;
 }
 
diff --git a/sound/pci/hda/hda_local.h b/sound/pci/hda/hda_local.h
index aaefa7c..04d730f 100644
--- a/sound/pci/hda/hda_local.h
+++ b/sound/pci/hda/hda_local.h
@@ -621,6 +621,7 @@ struct cea_sad {
 };
 
 #define ELD_FIXED_BYTES	20
+#define ELD_MAX_SIZE    256
 #define ELD_MAX_MNL	16
 #define ELD_MAX_SAD	16
 
@@ -645,6 +646,7 @@ struct hdmi_eld {
 	int	spk_alloc;
 	int	sad_count;
 	struct cea_sad sad[ELD_MAX_SAD];
+	char    eld_buffer[ELD_MAX_SIZE];
 #ifdef CONFIG_PROC_FS
 	struct snd_info_entry *proc_entry;
 #endif
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 3f1f6ac..3425401 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -324,6 +324,66 @@ static int cvt_nid_to_cvt_index(struct hdmi_spec *spec, hda_nid_t cvt_nid)
 	return -EINVAL;
 }
 
+static int hdmi_eld_ctl_info(struct snd_kcontrol *kcontrol,
+			struct snd_ctl_elem_info *uinfo)
+{
+	struct hda_codec *codec = snd_kcontrol_chip(kcontrol);
+	struct hdmi_spec *spec;
+	int pin_idx;
+
+	spec = codec->spec;
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_BYTES;
+
+	pin_idx = kcontrol->private_value;
+	uinfo->count = spec->pins[pin_idx].sink_eld.eld_size;
+
+	return 0;
+}
+
+static int hdmi_eld_ctl_get(struct snd_kcontrol *kcontrol,
+			struct snd_ctl_elem_value *ucontrol)
+{
+	struct hda_codec *codec = snd_kcontrol_chip(kcontrol);
+	struct hdmi_spec *spec;
+	int pin_idx;
+
+	spec = codec->spec;
+	pin_idx = kcontrol->private_value;
+
+	memcpy(ucontrol->value.bytes.data,
+		spec->pins[pin_idx].sink_eld.eld_buffer, ELD_MAX_SIZE);
+
+	return 0;
+}
+
+static struct snd_kcontrol_new eld_bytes_ctl = {
+	.access = SNDRV_CTL_ELEM_ACCESS_READ | SNDRV_CTL_ELEM_ACCESS_VOLATILE,
+	.iface = SNDRV_CTL_ELEM_IFACE_PCM,
+	.name = "ELD",
+	.info = hdmi_eld_ctl_info,
+	.get = hdmi_eld_ctl_get,
+};
+
+static int hdmi_create_eld_ctl(struct hda_codec *codec, int pin_idx,
+			int device)
+{
+	struct snd_kcontrol *kctl;
+	struct hdmi_spec *spec = codec->spec;
+	int err;
+
+	kctl = snd_ctl_new1(&eld_bytes_ctl, codec);
+	if (!kctl)
+		return -ENOMEM;
+	kctl->private_value = pin_idx;
+	kctl->id.device = device;
+
+	err = snd_hda_ctl_add(codec, spec->pins[pin_idx].pin_nid, kctl);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
 #ifdef BE_PARANOID
 static void hdmi_get_dip_index(struct hda_codec *codec, hda_nid_t pin_nid,
 				int *packet_index, int *byte_index)
@@ -1193,6 +1253,14 @@ static int generic_hdmi_build_controls(struct hda_codec *codec)
 		if (err < 0)
 			return err;
 		snd_hda_spdif_ctls_unassign(codec, pin_idx);
+
+		/* add control for ELD Bytes */
+		err = hdmi_create_eld_ctl(codec,
+					pin_idx,
+					spec->pcm_rec[pin_idx].device);
+
+		if (err < 0)
+			return err;
 	}
 
 	return 0;
-- 
1.7.6.2