floss: prefer HW-MSBC over SW-LC3 when CRAS prefers offloading

Some complications (see b/316077719) made Corsola a special case that
can report SW-LC3 availability offered by the peer and the BT stack,
which in fact should be ignored, but wasn't, due to CRAS allowing to
bypass its offloading decision when LC3 is supported.

BUG=b:347936346
TEST=Verify Pixel Buds Pro HFP works on Corsola
TEST=Verify Pixel Buds Pro HFP works on Kukui
TEST=Verify Pixel Buds Pro HFP works on Brya

Change-Id: I223657c75c5847e3b87150807ff9a40d54e56275
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/5692243
Tested-by: [email protected] <[email protected]>
Reviewed-by: Hsinyu Chao <[email protected]>
Commit-Queue: Jeremy Wu <[email protected]>

Author: Jeremy Wu

cras/src/server/cras_hfp_manager.c

@@ -131,15 +131,16 @@ struct cras_hfp* cras_floss_hfp_create(struct fl_media* fm,
     hfp->hfp_caps &= ~HFP_CODEC_FORMAT_MSBC;
   }
 
-  // Currently, SWB is only supported via SW encoding. If CRAS would
-  // have been using HW encoding but LC3 is available, we will back off to
-  // the SW encoding backend.
+  // Currently, SWB is only supported via SW encoding. We shall respect
+  // the offloading decision from CRAS because the capabilities exposed
+  // from the BT stack can be wrong for this particular case (on Corsola).
+  // See b/316077719 for details.
   if (cras_floss_hfp_is_codec_format_supported(
           hfp, HFP_CODEC_FORMAT_LC3_TRANSPARENT) &&
       hfp->sco_pcm_used) {
-    hfp->sco_pcm_used = false;
-    syslog(LOG_INFO, "Bypassed offloading to allow LC3");
-    // TODO: add UMA for this case
+    syslog(LOG_INFO, "Prefer HW-MSBC over SW-LC3 to respect offload decision");
+    hfp->hfp_caps |= HFP_CODEC_FORMAT_MSBC;
+    hfp->hfp_caps &= ~HFP_CODEC_FORMAT_LC3_TRANSPARENT;
   }
 
   if (hfp->sco_pcm_used) {