Implement support for dB gain display in alsamixer.

include/control.h

@@ -504,6 +504,7 @@ int snd_hctl_elem_write(snd_hctl_elem_t *elem, snd_ctl_elem_value_t * value);
 int snd_hctl_elem_tlv_read(snd_hctl_elem_t *elem, unsigned int *tlv, unsigned int tlv_size);
 int snd_hctl_elem_tlv_write(snd_hctl_elem_t *elem, const unsigned int *tlv);
 int snd_hctl_elem_tlv_command(snd_hctl_elem_t *elem, const unsigned int *tlv);
+int snd_hctl_elem_get_db_gain(snd_hctl_elem_t *elem, long volume, long *db_gain);
 
 snd_hctl_t *snd_hctl_elem_get_hctl(snd_hctl_elem_t *elem);
 

src/control/hcontrol.c

@@ -787,6 +787,114 @@ int snd_hctl_handle_events(snd_hctl_t *hctl)
 	return count;
 }
 
+static int snd_hctl_elem_decode_tlv_db_gain(unsigned int *tlv, unsigned int tlv_size, long volume, long *db_gain)
+{
+	unsigned int type;
+	unsigned int size;
+	unsigned int idx = 0;
+	int err = 0;
+
+	type = tlv[idx++];
+	size = tlv[idx++];
+	tlv_size -= 2 * sizeof(unsigned int);
+	if (size > tlv_size) {
+		printf("TLV size error (%i, %i, %i)!\n", type, size, tlv_size);
+		err=-EINVAL;
+		goto __exit_decode_db_gain;
+	}
+	switch (type) {
+	case SND_CTL_TLVT_CONTAINER:
+		size += sizeof(unsigned int) -1;
+		size /= sizeof(unsigned int);
+		printf("TLV container!\n");
+		while (idx < size) {
+			if (tlv[idx+1] > (size - idx) * sizeof(unsigned int)) {
+				printf("TLV size error in compound!\n");
+				err=-EINVAL;
+				goto __exit_decode_db_gain;
+			}
+			err = snd_hctl_elem_decode_tlv_db_gain(tlv + idx, tlv[idx+1], volume, db_gain);
+			if (!err) break; /* db_gain obtained */
+			idx += 2 + (tlv[1] + sizeof(unsigned int) - 1) / sizeof(unsigned int);
+		}
+		break;
+	case SND_CTL_TLVT_DB_SCALE:
+		if (size != 2 * sizeof(unsigned int)) {
+			while (size > 0) {
+				printf("0x%x", tlv[idx++]);
+				size -= sizeof(unsigned int);
+			}
+			printf("\n");
+		} else {
+			int min,step,mute;
+			min = tlv[2];
+			step = (tlv[3] & 0xffff);
+			mute = (tlv[3] >> 16) & 1;
+			*db_gain = (volume * step) + min;
+			if (mute && (volume == 0)) *db_gain = -9999999;
+		}
+		break;
+	default:
+		printf("unk-%i-", type);
+		while (size > 0) {
+			printf("0x%x", tlv[idx++]);
+			size -= sizeof(unsigned int);
+		}
+		printf("\n");
+		break;
+	}
+
+	__exit_decode_db_gain:
+	return err;
+}
+
+/**
+ * \brief Get db_gain information for an HCTL element
+ * \param elem HCTL element
+ * \param volume The current control volume
+ * \param db_gain The return value in db_gain scale
+ * \return 0 otherwise a negative error code on failure
+ */
+int snd_hctl_elem_get_db_gain(snd_hctl_elem_t *elem, long volume, long *db_gain)
+{
+	snd_ctl_elem_info_t *info;
+	unsigned int *tlv;
+	unsigned int tlv_size=4096;
+	unsigned int type;
+	unsigned int size;
+	unsigned int idx = 0;
+	int err=0;
+
+	snd_ctl_elem_info_alloca(&info);
+	snd_hctl_elem_info(elem, info);
+
+	if (tlv_size < 2 * sizeof(unsigned int)) {
+		printf("TLV size error!\n");
+		err=-EINVAL;
+		goto __exit_db_gain;
+	}
+	if (!snd_ctl_elem_info_is_tlv_readable(info)) {
+		err=-EINVAL;
+		goto __exit_db_gain;
+	}
+	tlv = malloc(4096);
+	if ((err = snd_hctl_elem_tlv_read(elem, tlv, tlv_size)) < 0) {
+		printf("Control element TLV read error: %s\n", snd_strerror(err));
+		goto __free_exit_db_gain;
+	}
+	err = snd_hctl_elem_decode_tlv_db_gain(tlv, tlv_size, volume, db_gain);
+
+	__free_exit_db_gain:
+	free(tlv);
+	__exit_db_gain:
+	return err;
+}
+	
+
+
+
+
+
 /**
  * \brief Get information for an HCTL element
  * \param elem HCTL element

src/mixer/simple_none.c

@@ -971,12 +971,37 @@ static int get_volume_ops(snd_mixer_elem_t *elem, int dir,
 	return 0;
 }
 
-static int get_dB_ops(snd_mixer_elem_t *elem ATTRIBUTE_UNUSED,
-		      int dir ATTRIBUTE_UNUSED,
-		      snd_mixer_selem_channel_id_t channel ATTRIBUTE_UNUSED,
-		      long *value ATTRIBUTE_UNUSED)
+static int get_dB_ops(snd_mixer_elem_t *elem,
+                      int dir,
+                      snd_mixer_selem_channel_id_t channel,
+                      long *value)
 {
-	return -ENXIO;
+	selem_none_t *s = snd_mixer_elem_get_private(elem);
+	selem_ctl_t *c;
+	int err = -EINVAL;
+	long volume, db_gain;
+	if (dir == SM_PLAY) {
+		c = &s->ctls[CTL_PLAYBACK_VOLUME];
+		if (c->type != 2) {
+			goto _err;
+		}
+	} else if (dir == SM_CAPT) {
+		c = &s->ctls[CTL_CAPTURE_VOLUME];
+		if (c->type != 2) {
+			goto _err;
+		}
+	} else goto _err;
+	if (err = get_volume_ops(elem, dir, channel, &volume))  {
+		goto _err;
+	}
+	if ((err = snd_hctl_elem_get_db_gain(c->elem, volume, &db_gain)) < 0) {
+		goto _err;
+	}
+	err = 0;
+	*value = db_gain;
+_err:
+	//if (err) printf("get_dB_ops:err=%d\n",err);
+	return err;
 }
 
 static int get_switch_ops(snd_mixer_elem_t *elem, int dir,