From d1328e694e8738550f7aa6661ec245a61b8bc279 Mon Sep 17 00:00:00 2001
From: Martin Lund <martin.lund@keep-it-simple.com>
Date: Sun, 11 May 2025 07:11:07 +0200
Subject: [PATCH] Fix write in non-interactive piping mode

So that piping does not break when write buffer is full because e.g.
device has flow control enabled and can't keep up.
---
 src/tty.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/tty.c b/src/tty.c
index c5e6876..6bd6f91 100644
--- a/src/tty.c
+++ b/src/tty.c
@@ -2641,6 +2641,19 @@ int tty_connect(void)
     /* If stdin is a pipe forward all input to tty device */
     if (interactive_mode == false)
     {
+        // Set blocking mode for serial device (blocking write)
+        int flags = fcntl(device_fd, F_GETFL, 0);
+        if (flags == -1)
+        {
+            tio_error_printf("Could not read descriptor flags (%s)", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+        if (fcntl(device_fd, F_SETFL, flags & ~O_NONBLOCK) == -1)
+        {
+            tio_error_printf("Could not set descriptor flags (%s)", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+
         while (true)
         {
             int ret = read(pipefd[0], &input_char, 1);