From 6b8670fe8fc17115a2d20b4eabb9139cc4cde38e Mon Sep 17 00:00:00 2001
From: Nick Brassel <nick@tzarc.org>
Date: Thu, 10 Apr 2025 10:43:25 +1000
Subject: [PATCH] Cater for use of `__errno_r()` in ChibiOS syscalls.c with
 newer picolibc revisions (#25121)

---
 platforms/chibios/errno.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 platforms/chibios/errno.h

diff --git a/platforms/chibios/errno.h b/platforms/chibios/errno.h
new file mode 100644
index 00000000000..a411ed98212
--- /dev/null
+++ b/platforms/chibios/errno.h
@@ -0,0 +1,13 @@
+// Copyright 2025 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+#include_next <errno.h>
+
+// Newer versions of picolibc don't seem to provide `__errno_r(r)` in the header file, but is used by ChibiOS.
+#ifndef __errno_r
+#    ifdef __REENT_ERRNO
+#        define __errno_r(r) _REENT_ERRNO(r)
+#    else
+#        define __errno_r(r) (errno)
+#    endif
+#endif