Downmix: Fix setting an invalid channel mask has side effects

Attempting to set an invalid channel mask has the side effect
of actually setting it.  A legacy bug that should be fixed
because it can cause an invalid state of the downmixer.

Test: atest downmix_tests
Bug: 202162797
Change-Id: I6cc03c5bf68492e8442b5d1ae62b89c4a77c5916
diff --git a/media/libeffects/downmix/EffectDownmix.cpp b/media/libeffects/downmix/EffectDownmix.cpp
index 90bb410..4efab84 100644
--- a/media/libeffects/downmix/EffectDownmix.cpp
+++ b/media/libeffects/downmix/EffectDownmix.cpp
@@ -647,6 +647,12 @@
         ALOGE("Downmix_Configure error: invalid config");
         return -EINVAL;
     }
+    // when configuring the effect, do not allow a blank or unsupported channel mask
+    if (!Downmix_validChannelMask(pConfig->inputCfg.channels)) {
+        ALOGE("Downmix_Configure error: input channel mask(0x%x) not supported",
+                                                    pConfig->inputCfg.channels);
+        return -EINVAL;
+    }
 
     if (&pDwmModule->config != pConfig) {
         memcpy(&pDwmModule->config, pConfig, sizeof(effect_config_t));
@@ -657,12 +663,6 @@
         pDownmixer->apply_volume_correction = false;
         pDownmixer->input_channel_count = 8; // matches default input of AUDIO_CHANNEL_OUT_7POINT1
     } else {
-        // when configuring the effect, do not allow a blank or unsupported channel mask
-        if (!Downmix_validChannelMask(pConfig->inputCfg.channels)) {
-            ALOGE("Downmix_Configure error: input channel mask(0x%x) not supported",
-                                                        pConfig->inputCfg.channels);
-            return -EINVAL;
-        }
         pDownmixer->input_channel_count =
                 audio_channel_count_from_out_mask(pConfig->inputCfg.channels);
     }