From e255f0ff7e6bfc0e2cd9dc2d008a28ace81c3641 Mon Sep 17 00:00:00 2001
From: Xavier Chapron <xavier.chapron@ledger.fr>
Date: Wed, 7 Feb 2024 17:44:11 +0100
Subject: [PATCH] lib_standard_app/io.c: Send RAPDU immediately and use
 IO_CONTINUE_RX flag

---
 Makefile.standard_app |  6 ++++++
 lib_standard_app/io.c | 10 +++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Makefile.standard_app b/Makefile.standard_app
index a880033f0..a0be83a3d 100644
--- a/Makefile.standard_app
+++ b/Makefile.standard_app
@@ -124,6 +124,12 @@ ifneq ($(DISABLE_STANDARD_APP_FILES), 1)
 SDK_SOURCE_PATH += lib_standard_app
 endif
 
+ifneq ($(DISABLE_STANDARD_APP_SYNC_RAPDU), 1)
+ifneq ($(TARGET_NAME),TARGET_NANOS)
+DEFINES += STANDARD_APP_SYNC_RAPDU
+endif
+endif
+
 #####################################################################
 #                              NBGL                                 #
 #####################################################################
diff --git a/lib_standard_app/io.c b/lib_standard_app/io.c
index 57016ea75..27581c4fb 100644
--- a/lib_standard_app/io.c
+++ b/lib_standard_app/io.c
@@ -134,8 +134,8 @@ WEAK int io_recv_command()
 
     switch (G_io_state) {
         case READY:
+            ret        = io_exchange(CHANNEL_APDU | IO_CONTINUE_RX, G_output_len);
             G_io_state = RECEIVED;
-            ret        = io_exchange(CHANNEL_APDU, G_output_len);
             break;
         case RECEIVED:
             G_io_state = WAITING;
@@ -198,9 +198,17 @@ WEAK int io_send_response_buffers(const buffer_t *rdatalist, size_t count, uint1
             ret = -1;
             break;
         case RECEIVED:
+#ifdef STANDARD_APP_SYNC_RAPDU
+            // Send synchronously the APDU response.
+            // This is needed to send the response before displaying synchronous
+            // status message on the screen.
+            // This is not always done to spare the RAM (stack) on LNS.
+            __attribute__((fallthrough));
+#else
             G_io_state = READY;
             ret        = 0;
             break;
+#endif
         case WAITING:
             ret          = io_exchange(CHANNEL_APDU | IO_RETURN_AFTER_TX, G_output_len);
             G_output_len = 0;