switch-on-connect: Blacklist HDMI devices by default

As the comment says, switching to HDMI automatically often causes
problems. Commit bae8c16bfadb43c596b03f9c7ff7c9e9f1709b76
("switch-on-connect: Do not ignore HDMI sinks") enabled switching to
HDMI earlier. It was known already then that HDMI monitors don't
necessarily have speakers on them, but I accepted the patch on the
basis that module-switch-on-connect acts only if the card profile is
switched to HDMI, so if switching to HDMI is wrong, then already the
profile switch should cause problems. I didn't think of the case where
the default sink is on some other card, in which case switching the
profile on the HDMI card doesn't cause problems by itself.

I don't want to revert bae8c16bfa, because João needs to be able to
configure their systems to automatically switch to HDMI. Instead, this
patch utilizes the new blacklisting feature in module-switch-on-connect
to blacklist HDMI sinks by default. Switching to HDMI can be enabled by
setting the blacklist modarg to an empty string or something that
doesn't match HDMI sinks.

Fixes: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/issues/749

diff --git a/src/modules/module-switch-on-connect.c b/src/modules/module-switch-on-connect.c
index 583b645..950ecbe 100644 (file)
--- a/src/modules/module-switch-on-connect.c
+++ b/src/modules/module-switch-on-connect.c
@@ -33,6 +33,12 @@
 #include <pulsecore/namereg.h>
 #include <pulsecore/core-util.h>
 
+/* Ignore HDMI devices by default. HDMI monitors don't necessarily have audio
+ * output on them, and even if they do, waking up from sleep or changing
+ * monitor resolution may appear as a plugin event, which causes trouble if the
+ * user doesn't want to use the monitor for audio. */
+#define DEFAULT_BLACKLIST "hdmi"
+
 PA_MODULE_AUTHOR("Michael Terry");
 PA_MODULE_DESCRIPTION("When a sink/source is added, switch to it or conditionally switch to it");
 PA_MODULE_VERSION(PACKAGE_VERSION);
@@ -202,7 +208,14 @@ int pa__init(pa_module*m) {
         goto fail;
     }
 
-    u->blacklist = pa_xstrdup(pa_modargs_get_value(ma, "blacklist", NULL));
+    u->blacklist = pa_xstrdup(pa_modargs_get_value(ma, "blacklist", DEFAULT_BLACKLIST));
+
+    /* An empty string disables all blacklisting. */
+    if (!*u->blacklist) {
+        pa_xfree(u->blacklist);
+        u->blacklist = NULL;
+    }
+
     if (u->blacklist != NULL && !pa_is_regex_valid(u->blacklist)) {
         pa_log_error("A blacklist pattern was provided but is not a valid regex");
         pa_xfree(u->blacklist);