Write unity gain back with successful EFFECT_CMD_SET_VOLUME handling

Bug: 271500140
Test: Enable AIDL and flash to pixel
Test: Play Youtube music with effect on/off
Change-Id: I7e37a289f9c5f7773e500e59220963d1d17b5fb2
Merged-In: I7e37a289f9c5f7773e500e59220963d1d17b5fb2
diff --git a/media/libaudiohal/impl/EffectConversionHelperAidl.cpp b/media/libaudiohal/impl/EffectConversionHelperAidl.cpp
index 63bba24..4c58fe9 100644
--- a/media/libaudiohal/impl/EffectConversionHelperAidl.cpp
+++ b/media/libaudiohal/impl/EffectConversionHelperAidl.cpp
@@ -318,17 +318,25 @@
             mEffect->setParameter(Parameter::make<Parameter::deviceDescription>(aidlDevices))));
     return *static_cast<int32_t*>(pReplyData) = OK;
 }
+
 status_t EffectConversionHelperAidl::handleSetVolume(uint32_t cmdSize, const void* pCmdData,
-                                                     uint32_t* replySize __unused,
-                                                     void* pReplyData __unused) {
+                                                     uint32_t* replySize, void* pReplyData) {
     if (cmdSize != 2 * sizeof(uint32_t) || !pCmdData) {
         ALOGE("%s parameter invalid %u %p", __func__, cmdSize, pCmdData);
         return BAD_VALUE;
     }
-    Parameter::VolumeStereo volume = {.left = (float)(*(uint32_t*)pCmdData) / (1 << 24),
-                                      .right = (float)(*(uint32_t*)pCmdData + 1) / (1 << 24)};
+
+    constexpr uint32_t unityGain = 1 << 24;
+    Parameter::VolumeStereo volume = {.left = (float)(*(uint32_t*)pCmdData) / unityGain,
+                                      .right = (float)(*(uint32_t*)pCmdData + 1) / unityGain};
     RETURN_STATUS_IF_ERROR(statusTFromBinderStatus(
             mEffect->setParameter(Parameter::make<Parameter::volumeStereo>(volume))));
+
+    // write unity gain back if volume was successfully set
+    if (replySize && *replySize == 2 * sizeof(uint32_t) && pReplyData) {
+        constexpr uint32_t vol_ret[2] = {unityGain, unityGain};
+        memcpy(pReplyData, vol_ret, sizeof(vol_ret));
+    }
     return OK;
 }