ALSA: hda/hdmi: expose ELD control

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 <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/pci/hda/hda_eld.c

···
 	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;
 
···
 		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);
···
 	ret = hdmi_update_eld(eld, buf, size);
 
 error:
-	kfree(buf);
 	return ret;
 }
 

sound/pci/hda/hda_local.h

···
 };
 
 #define ELD_FIXED_BYTES	20
+#define ELD_MAX_SIZE    256
 #define ELD_MAX_MNL	16
 #define ELD_MAX_SAD	16
 
···
 	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

sound/pci/hda/patch_hdmi.c

···
 	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)
···
 		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;