From 91468ed36b5b698d157b665af2774ea73fb3103c Mon Sep 17 00:00:00 2001
From: Scott Shawcroft <scott@tannewt.org>
Date: Tue, 8 Mar 2022 17:55:21 -0800
Subject: [PATCH] Don't crash on early debug print

---
 supervisor/shared/serial.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/supervisor/shared/serial.c b/supervisor/shared/serial.c
index 7f948a8199..87c4fca14d 100644
--- a/supervisor/shared/serial.c
+++ b/supervisor/shared/serial.c
@@ -73,6 +73,11 @@ const mp_print_t debug_uart_print = {NULL, debug_uart_print_strn};
 
 int debug_uart_printf(const char *fmt, ...) {
     #if defined(CIRCUITPY_DEBUG_UART_TX)
+    // Skip prints that occur before debug serial is started. It's better than
+    // crashing.
+    if (common_hal_busio_uart_deinited(&debug_uart)) {
+        return 0;
+    }
     va_list ap;
     va_start(ap, fmt);
     int ret = mp_vprintf(&debug_uart_print, fmt, ap);