From e8d739fdd77bab43bb294f1a8ef2a3e278c89f91 Mon Sep 17 00:00:00 2001
From: Pauli Virtanen <pav@iki.fi>
Date: Sat, 6 Sep 2025 19:14:22 +0300
Subject: [PATCH] alsa: report extra latency for FireWire drivers

Based on testing, ALSA FireWire drivers introduce additional latency
determined by the buffer size.

Report that latency.

Pass device.bus to the node, so it can recognize firewire.
---
 spa/plugins/alsa/alsa-acp-device.c | 6 ++++--
 spa/plugins/alsa/alsa-pcm.c        | 9 +++++++++
 spa/plugins/alsa/alsa-pcm.h        | 1 +
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/spa/plugins/alsa/alsa-acp-device.c b/spa/plugins/alsa/alsa-acp-device.c
index 5d46feed4..9e5e8eeb1 100644
--- a/spa/plugins/alsa/alsa-acp-device.c
+++ b/spa/plugins/alsa/alsa-acp-device.c
@@ -160,7 +160,7 @@ static int emit_node(struct impl *this, struct acp_device *dev)
 	char codecs[512];
 	struct spa_device_object_info info;
 	struct acp_card *card = this->card;
-	const char *stream, *card_id;
+	const char *stream, *card_id, *bus;
 
 	info = SPA_DEVICE_OBJECT_INFO_INIT();
 	info.type = SPA_TYPE_INTERFACE_Node;
@@ -175,7 +175,7 @@ static int emit_node(struct impl *this, struct acp_device *dev)
 
 	info.change_mask = SPA_DEVICE_OBJECT_CHANGE_MASK_PROPS;
 
-	items = alloca((dev->props.n_items + 11) * sizeof(*items));
+	items = alloca((dev->props.n_items + 12) * sizeof(*items));
 	n_items = 0;
 
 	snprintf(card_index, sizeof(card_index), "%d", card->index);
@@ -193,6 +193,8 @@ static int emit_node(struct impl *this, struct acp_device *dev)
 	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_ALSA_PCM_STREAM, stream);
 	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_PORT_GROUP, stream);
 	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_ICON_NAME, "audio-card-analog");
+	bus = acp_dict_lookup(&card->props, SPA_KEY_DEVICE_BUS);
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_BUS, bus);
 
 	snprintf(channels, sizeof(channels), "%d", dev->format.channels);
 	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_AUDIO_CHANNELS, channels);
diff --git a/spa/plugins/alsa/alsa-pcm.c b/spa/plugins/alsa/alsa-pcm.c
index c76e798b7..cea6d3e44 100644
--- a/spa/plugins/alsa/alsa-pcm.c
+++ b/spa/plugins/alsa/alsa-pcm.c
@@ -1005,6 +1005,8 @@ int spa_alsa_init(struct state *state, const struct spa_dict *info)
 			state->num_bind_ctls = i;
 
 			/* We'll do the actual binding after checking the card exists */
+		} else if (spa_streq(k, SPA_KEY_DEVICE_BUS)) {
+			state->is_firewire = spa_streq(s, "firewire");
 		} else {
 			alsa_set_param(state, k, s);
 		}
@@ -2052,6 +2054,13 @@ static void recalc_headroom(struct state *state)
 	if (rate != 0 && state->rate != 0)
 		latency = SPA_SCALE32_UP(latency, rate, state->rate);
 
+	if (state->is_firewire) {
+		/* XXX: For ALSA FireWire drivers, unlike for other ALSA drivers, buffer size
+		 * XXX: contributes extra latency (as of kernel 6.16).
+		 */
+		latency += state->buffer_frames;
+	}
+
 	state->latency[state->port_direction].min_rate =
 		state->latency[state->port_direction].max_rate = latency;
 }
diff --git a/spa/plugins/alsa/alsa-pcm.h b/spa/plugins/alsa/alsa-pcm.h
index bd77abc2e..576144bfe 100644
--- a/spa/plugins/alsa/alsa-pcm.h
+++ b/spa/plugins/alsa/alsa-pcm.h
@@ -155,6 +155,7 @@ struct state {
 	unsigned int disable_batch:1;
 	unsigned int disable_tsched:1;
 	unsigned int is_split_parent:1;
+	unsigned int is_firewire:1;
 	char clock_name[64];
 	uint32_t quantum_limit;