alsa_sound: Fix handling of zero size write request

Previously, periodSize number of bytes from the buffer pointer
location were always written to PCM even in the case when the
write call specified 0 bytes buffer size.
This caused short pop noise at the beginning of the playback
after the "audio flinger: force audio path start from normal mixer"
fake write() of 0 bytes introduction in audioflinger.

RM-208
Change-Id: Ifeb353fed01a2f2b7e771a7ccb7d422f77a69228
(cherry picked from commit cb0a9ef95d65dc5d872e15afeac9c6b2fc74c51b)

1 files changed, 4 insertions, 0 deletions

diff --git a/legacy/alsa_sound/AudioStreamOutALSA.cpp b/legacy/alsa_sound/AudioStreamOutALSA.cpp
index 0db56494..9d6ea89e 100644
--- a/legacy/alsa_sound/AudioStreamOutALSA.cpp
+++ b/legacy/alsa_sound/AudioStreamOutALSA.cpp
@@ -112,6 +112,10 @@ ssize_t AudioStreamOutALSA::write(const void *buffer, size_t bytes)
 
     int write_pending = bytes;
 
+    if (bytes == 0) {
+        return 0;
+    }
+
     if((strcmp(mHandle->useCase, SND_USE_CASE_VERB_IP_VOICECALL)) &&
        (strcmp(mHandle->useCase, SND_USE_CASE_MOD_PLAY_VOIP))) {
         mParent->mLock.lock();