From ed88cad583c0fdef52b456dcdb86d6d38bbc3061 Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fvogt@suse.de>
Date: Wed, 13 Jul 2022 10:47:22 +0200
Subject: [PATCH] spa/alsa-udev: Check accessibility of pcm devices as well

The order of attribute changes is random, so it's possible that controlCX is
accessible before the other devices, which marks the device as available but it
actually fails to open. Only consider the device accessible if both control and
PCM devices can be accessed.

This requires reacting to ATTRIB changes of pcm devices as well now.

Fixes #2534
---
 spa/plugins/alsa/alsa-udev.c | 34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/spa/plugins/alsa/alsa-udev.c b/spa/plugins/alsa/alsa-udev.c
index aa7b03994..8ee217d9d 100644
--- a/spa/plugins/alsa/alsa-udev.c
+++ b/spa/plugins/alsa/alsa-udev.c
@@ -538,11 +538,35 @@ static int emit_object_info(struct impl *this, struct device *device)
 
 static bool check_access(struct impl *this, struct device *device)
 {
-	char path[128];
-	bool accessible;
+	char path[128], prefix[32];
+	DIR *snd = NULL;
+	struct dirent *entry;
+	bool accessible = false;
 
 	snprintf(path, sizeof(path), "/dev/snd/controlC%u", device->id);
-	accessible = access(path, R_OK|W_OK) >= 0;
+	if (access(path, R_OK|W_OK) >= 0 && (snd = opendir("/dev/snd"))) {
+		/*
+		 * It's possible that controlCX is accessible before pcmCX* or
+		 * the other way around. Return true only if all devices are
+                 * accessible.
+		 */
+
+		accessible = true;
+		spa_scnprintf(prefix, sizeof(prefix), "pcmC%uD", device->id);
+		while ((entry = readdir(snd)) != NULL) {
+			if (!(entry->d_type == DT_CHR &&
+					spa_strstartswith(entry->d_name, prefix)))
+				continue;
+
+			snprintf(path, sizeof(path), "/dev/snd/%.32s", entry->d_name);
+			if (access(path, R_OK|W_OK) < 0) {
+				accessible = false;
+				break;
+			}
+		}
+		closedir(snd);
+	}
+
 	if (accessible != device->accessible)
 		spa_log_debug(this->log, "%s accessible:%u", path, accessible);
 	device->accessible = accessible;
@@ -655,10 +679,6 @@ static void impl_on_notify_events(struct spa_source *source)
 			/* Device becomes accessible or not busy */
 			if ((event->mask & (IN_ATTRIB | IN_CLOSE_WRITE))) {
 				bool access;
-
-				if ((event->mask & IN_ATTRIB) &&
-						spa_strstartswith(event->name, "pcm"))
-					continue;
 				if (sscanf(event->name, "controlC%u", &id) != 1 &&
 						sscanf(event->name, "pcmC%uD", &id) != 1)
 					continue;