From f31d5a93b517a5b233871e93811cb7da0a099d2d Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Mon, 6 Feb 2023 10:37:29 +0100
Subject: [PATCH 1/3] sys/fmt: `print()`: use `fflush(); stdio_write()` vs.
 `fwrite()`

---
 sys/fmt/fmt.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/sys/fmt/fmt.c b/sys/fmt/fmt.c
index 11eddf3cfa..c1d6386550 100644
--- a/sys/fmt/fmt.c
+++ b/sys/fmt/fmt.c
@@ -27,6 +27,7 @@
 
 #include "kernel_defines.h"
 #include "fmt.h"
+#include "stdio_base.h"
 
 static const char _hex_chars[16] = "0123456789ABCDEF";
 
@@ -506,25 +507,24 @@ uint32_t scn_u32_hex(const char *str, size_t n)
     return res;
 }
 
+/* native gets special treatment as native's stdio code is ... special.
+ * And when not building for RIOT, there's no `stdio_write()`.
+ * In those cases, just defer to `printf()`.
+ */
+#if IS_USED(MODULE_STDIO_NATIVE) || !defined(RIOT_VERSION)
 void print(const char *s, size_t n)
 {
-    if (IS_USED(MODULE_STDIO_NATIVE)) {
-        /* native gets special treatment as native's stdio code is ...
-         * special */
-        printf("%.*s", (int)n, s);
-        return;
-    }
-
-    while (n > 0) {
-        ssize_t written;
-        written = fwrite(s, 1, n, stdout);
-        if (written < 0) {
-            break;
-        }
-        n -= written;
-        s += written;
-    }
+    printf("%.*s", (int)n, s);
 }
+#else
+void print(const char *s, size_t n)
+{
+    /* flush the libc's output buffer so output is not intermingled. */
+    fflush(stdout);
+
+    stdio_write(s, n);
+}
+#endif
 
 void print_u32_dec(uint32_t val)
 {

From c77b104c2dca40a0ca21b1fc66aa7312c2552f73 Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Mon, 6 Feb 2023 10:38:18 +0100
Subject: [PATCH 2/3] sys/test_utils/print_stack_usage: reduce `MIN_SIZE` for
 fmt

---
 sys/test_utils/print_stack_usage/print_stack_usage.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/test_utils/print_stack_usage/print_stack_usage.c b/sys/test_utils/print_stack_usage/print_stack_usage.c
index 6b67d6d1ac..b4e8f7c776 100644
--- a/sys/test_utils/print_stack_usage/print_stack_usage.c
+++ b/sys/test_utils/print_stack_usage/print_stack_usage.c
@@ -26,7 +26,11 @@
 #include <stdio.h>
 #endif
 
+#if MODULE_FMT
+# define MIN_SIZE   (THREAD_STACKSIZE_TINY)
+#else
 # define MIN_SIZE   (THREAD_STACKSIZE_TINY + THREAD_EXTRA_STACKSIZE_PRINTF)
+#endif
 
 void print_stack_usage_metric(const char *name, void *stack, unsigned max_size)
 {
@@ -37,7 +41,7 @@ void print_stack_usage_metric(const char *name, void *stack, unsigned max_size)
 #if MODULE_FMT
         print_str("{ \"threads\": [{ \"name\": \"");
         print_str(name);
-        print_str(", \"stack_size\": ");
+        print_str("\", \"stack_size\": ");
         print_u32_dec(max_size);
         print_str(", \"stack_used\": ");
         print_u32_dec(max_size - free);

From c27010c63046870c30d7bc7b8fb98ddd5be0aefb Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@bht-berlin.de>
Date: Tue, 7 Feb 2023 22:40:38 +0100
Subject: [PATCH 3/3] sys/stdio: mark stdio_tinyusb_cdc_acm as buffered

stdio_tinyusb_cdc_acm benefits from stdio buffering (not transferring
individual bytes) just like stdio_cdc_acm.
---
 makefiles/stdio.inc.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/makefiles/stdio.inc.mk b/makefiles/stdio.inc.mk
index e641523145..9749c34177 100644
--- a/makefiles/stdio.inc.mk
+++ b/makefiles/stdio.inc.mk
@@ -82,7 +82,7 @@ endif
 
 # enable stdout buffering for modules that benefit from sending out buffers in larger chunks
 ifneq (,$(filter picolibc,$(USEMODULE)))
-  ifneq (,$(filter stdio_cdc_acm stdio_ethos slipdev_stdio stdio_semihosting,$(USEMODULE)))
+  ifneq (,$(filter stdio_cdc_acm stdio_ethos slipdev_stdio stdio_semihosting stdio_tinyusb_cdc_acm,$(USEMODULE)))
     USEMODULE += picolibc_stdout_buffered
   endif
 endif