[PULL 18/35] paaudio: reduce effective playback buffer size

[Gerd Hoffmann <kraxel@redhat.com>]

From: Volker Rümelin <vr_qemu@t-online.de>

Add the buffer_get_free pcm_ops function to reduce the effective
playback buffer size. All intermediate audio playback buffers
become temporary buffers.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20220301191311.26695-11-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 audio/paaudio.c | 47 +++++++++++++++++++++++++++++++----------------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/audio/paaudio.c b/audio/paaudio.c
index 9df1e69c086f..d94f858ec761 100644
--- a/audio/paaudio.c
+++ b/audio/paaudio.c
@@ -201,39 +201,53 @@ unlock_and_fail:
     return 0;
 }
 
+static size_t qpa_buffer_get_free(HWVoiceOut *hw)
+{
+    PAVoiceOut *p = (PAVoiceOut *)hw;
+    PAConnection *c = p->g->conn;
+    size_t l;
+
+    pa_threaded_mainloop_lock(c->mainloop);
+
+    CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
+                    "pa_threaded_mainloop_lock failed\n");
+    if (pa_stream_get_state(p->stream) != PA_STREAM_READY) {
+        /* wait for stream to become ready */
+        l = 0;
+        goto unlock;
+    }
+
+    l = pa_stream_writable_size(p->stream);
+    CHECK_SUCCESS_GOTO(c, l != (size_t) -1, unlock_and_fail,
+                       "pa_stream_writable_size failed\n");
+
+unlock:
+    pa_threaded_mainloop_unlock(c->mainloop);
+    return l;
+
+unlock_and_fail:
+    pa_threaded_mainloop_unlock(c->mainloop);
+    return 0;
+}
+
 static void *qpa_get_buffer_out(HWVoiceOut *hw, size_t *size)
 {
-    PAVoiceOut *p = (PAVoiceOut *) hw;
+    PAVoiceOut *p = (PAVoiceOut *)hw;
     PAConnection *c = p->g->conn;
     void *ret;
-    size_t l;
     int r;
 
     pa_threaded_mainloop_lock(c->mainloop);
 
     CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
                     "pa_threaded_mainloop_lock failed\n");
-    if (pa_stream_get_state(p->stream) != PA_STREAM_READY) {
-        /* wait for stream to become ready */
-        l = 0;
-        ret = NULL;
-        goto unlock;
-    }
-
-    l = pa_stream_writable_size(p->stream);
-    CHECK_SUCCESS_GOTO(c, l != (size_t) -1, unlock_and_fail,
-                       "pa_stream_writable_size failed\n");
 
     *size = -1;
     r = pa_stream_begin_write(p->stream, &ret, size);
     CHECK_SUCCESS_GOTO(c, r >= 0, unlock_and_fail,
                        "pa_stream_begin_write failed\n");
 
-unlock:
     pa_threaded_mainloop_unlock(c->mainloop);
-    if (*size > l) {
-        *size = l;
-    }
     return ret;
 
 unlock_and_fail:
@@ -901,6 +915,7 @@ static struct audio_pcm_ops qpa_pcm_ops = {
     .init_out = qpa_init_out,
     .fini_out = qpa_fini_out,
     .write    = qpa_write,
+    .buffer_get_free = qpa_buffer_get_free,
     .get_buffer_out = qpa_get_buffer_out,
     .put_buffer_out = qpa_put_buffer_out,
     .volume_out = qpa_volume_out,
-- 
2.35.1