!68 alsa-mixer: avoid assertion at alsa-lib mixer API when element removal

From: @wuxu_buque 
Reviewed-by: @liqingqing_1229 
Signed-off-by: @liqingqing_1229

0001-alsa-mixer-avoid-assertion-at-alsa-lib-mixer-API-whe.patch

@@ -0,0 +1,59 @@
+From 4bdf4c99662f3da0e58d6c04bafff95d84362922 Mon Sep 17 00:00:00 2001
+From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
+Date: Mon, 27 Jun 2022 10:09:52 +0900
+Subject: [PATCH] alsa-mixer: avoid assertion at alsa-lib mixer API when
+ element removal
+
+PulseAudio v5.99 or later hits assertion at alsa-lib mixer API due to
+wrong handling of removal event for mixer element.
+
+pulseaudio: mixer.c:149: hctl_elem_event_handler: Assertion `bag_empty(bag)' failed.
+
+The removal event is defined as '~0U', thus it's not distinguished from
+the other type of event just by bitwise operator.
+
+At the removal event, class implementator for mixer API should detach
+mixer element from hcontrol element in callback handler since alsa-lib
+has assertion to check the list of mixer elements for a hcontrol element
+is empty or not after calling all of handlers. In detail, please refer to
+MR to alsa-lib:
+
+ * https://github.com/alsa-project/alsa-lib/pull/244
+
+This commit fixes the above two issues. The issue can be regenerated by
+`samples/ctl` Python 3 script of alsa-gobject.
+
+ * https://github.com/alsa-project/alsa-gobject/
+
+It adds some user-defined elements into sound card 0. When terminated by
+SIGINT signal, it removes the elements. Then PulseAudio dies due to the
+assertion.
+
+Fixes: 1fd8848e64cf ("alsa-util: Add functions for accessing mixer elements through mixer class")
+Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/728>
+---
+ src/modules/alsa/alsa-util.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c
+index 7dc373fa0..f4e838d37 100644
+--- a/src/modules/alsa/alsa-util.c
++++ b/src/modules/alsa/alsa-util.c
+@@ -1654,7 +1654,13 @@ static int mixer_class_event(snd_mixer_class_t *class, unsigned int mask,
+ {
+     int err;
+     const char *name = snd_hctl_elem_get_name(helem);
+-    if (mask & SND_CTL_EVENT_MASK_ADD) {
++    /* NOTE: The remove event is defined as '~0U`. */
++    if (mask == SND_CTL_EVENT_MASK_REMOVE) {
++        /* NOTE: Unless we remove the pointer to melem from the linked-list at
++         * private_data of helem, an assertion will be hit in alsa-lib since
++         * the list is not empty. */
++        snd_mixer_elem_detach(melem, helem);
++    } else if (mask & SND_CTL_EVENT_MASK_ADD) {
+         snd_ctl_elem_iface_t iface = snd_hctl_elem_get_interface(helem);
+         if (iface == SND_CTL_ELEM_IFACE_CARD || iface == SND_CTL_ELEM_IFACE_PCM) {
+             snd_mixer_elem_t *new_melem;
+-- 
+2.33.0
+

pulseaudio.spec

@@ -15,6 +15,7 @@ Source5:        default.pa-for-gdm
 
 Patch201:       pulseaudio-autostart.patch
 Patch1001:      0001-Fix-the-problem-that-the-description-field-of-pa_als.patch
+Patch1002:	0001-alsa-mixer-avoid-assertion-at-alsa-lib-mixer-API-whe.patch
 
 BuildRequires:	meson
 BuildRequires:  automake libtool gcc-c++ bash-completion
@@ -242,6 +243,9 @@ exit 0
 %{_mandir}/man*/*
 
 %changelog
+* Mon Dec 12 2022 wuxu <wuxu.wu@huawei.com> - 16.1-4
+- alsa-mixer: avoid assertion at alsa-lib mixer API when element removal
+
 * Tue Oct 18 2022 Liu Zixian <liuzixian4@huawei.com> - 16.1-4
 - delete unused BuildRequires