From 149471631ee97da561bdd1b1d95ad1a7e54846c2 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Mon, 29 Mar 2021 17:05:03 +0200
Subject: [PATCH] alsa: use higher ports for listening

Allocate up to the first 16 ports, use the last 2 ports and free the
first 14 ports.

This ensure our ports are not among the first ports so that port 128
and following are for normal apps, what is usually expected when
PipeWire is not running.

Fixes #951
---
 spa/plugins/alsa/alsa-seq.c | 44 ++++++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/spa/plugins/alsa/alsa-seq.c b/spa/plugins/alsa/alsa-seq.c
index f6799391b..ac8c7e399 100644
--- a/spa/plugins/alsa/alsa-seq.c
+++ b/spa/plugins/alsa/alsa-seq.c
@@ -47,8 +47,6 @@
 static int seq_open(struct seq_state *state, struct seq_conn *conn, bool with_queue)
 {
 	struct props *props = &state->props;
-	struct pollfd pfd;
-        snd_seq_port_info_t *pinfo;
 	int res;
 
 	spa_log_debug(state->log, "%p: ALSA seq open '%s' duplex", state, props->device);
@@ -57,9 +55,16 @@ static int seq_open(struct seq_state *state, struct seq_conn *conn, bool with_qu
 			   props->device,
 			   SND_SEQ_OPEN_DUPLEX,
 			   0)) < 0) {
-		spa_log_error(state->log, "open failed: %s", snd_strerror(res));
 		return res;
 	}
+	return 0;
+}
+
+static int seq_init(struct seq_state *state, struct seq_conn *conn, bool with_queue)
+{
+	struct pollfd pfd;
+	snd_seq_port_info_t *pinfo;
+	int res;
 
 	/* client id */
 	if ((res = snd_seq_client_id(conn->hndl)) < 0) {
@@ -249,10 +254,11 @@ static void alsa_seq_on_sys(struct spa_source *source)
 
 int spa_alsa_seq_open(struct seq_state *state)
 {
-	int res;
+	int n, i, res;
 	snd_seq_port_subscribe_t *sub;
 	snd_seq_addr_t addr;
 	snd_seq_queue_timer_t *timer;
+	struct seq_conn reserve[16];
 
 	if (state->opened)
 		return 0;
@@ -260,13 +266,32 @@ int spa_alsa_seq_open(struct seq_state *state)
 	init_stream(state, SPA_DIRECTION_INPUT);
 	init_stream(state, SPA_DIRECTION_OUTPUT);
 
-	if ((res = seq_open(state, &state->sys, false)) < 0)
+	for (i = 0; i < 16; i++) {
+		spa_log_debug(state->log, "close %d", i);
+		if ((res = seq_open(state, &reserve[i], false)) < 0)
+			break;
+	}
+	if (i >= 2) {
+		state->event = reserve[--i];
+		state->sys = reserve[--i];
+		res = 0;
+	}
+	for (n = --i; n >= 0; n--) {
+		spa_log_debug(state->log, "close %d", n);
+		seq_close(state, &reserve[n]);
+	}
+	if (res < 0) {
+		spa_log_error(state->log, "open failed: %s", snd_strerror(res));
 		return res;
+	}
+
+	if ((res = seq_init(state, &state->sys, false)) < 0)
+		goto error_close;
 
 	snd_seq_set_client_name(state->sys.hndl, "PipeWire-System");
 
-	if ((res = seq_open(state, &state->event, true)) < 0)
-		goto error_close_sys;
+	if ((res = seq_init(state, &state->event, true)) < 0)
+		goto error_close;
 
 	snd_seq_set_client_name(state->event.hndl, "PipeWire-RT-Event");
 
@@ -305,7 +330,7 @@ int spa_alsa_seq_open(struct seq_state *state)
 
 	if ((res = spa_system_timerfd_create(state->data_system,
 			CLOCK_MONOTONIC, SPA_FD_CLOEXEC | SPA_FD_NONBLOCK)) < 0)
-		goto error_close_event;
+		goto error_close;
 
 	state->timerfd = res;
 
@@ -313,9 +338,8 @@ int spa_alsa_seq_open(struct seq_state *state)
 
 	return 0;
 
-error_close_event:
+error_close:
 	seq_close(state, &state->event);
-error_close_sys:
 	seq_close(state, &state->sys);
 	return res;
 }