diff mbox series

[Concept,03/21] sandbox: serial: Report output failurs

Message ID 20251214175449.3799539-4-sjg@u-boot.org
State New
Headers
Series test: Add support for passing arguments to C unit tests |

Commit Message

Simon Glass Dec. 14, 2025, 5:54 p.m. UTC 
  From: Simon Glass <simon.glass@canonical.com>

When characters cannot be sent to the serial port, return an error code
so that the uclass can try again.

This fixes a problem with gnome-terminal which seems to get behind and
then drop output when a large amount of output is produced quickly (e.g.
100K in under a second). Since sandbox often writes to the device one
character at a time it does place a substantial load on the other end of
the PTY. Quite possibly it does not empty the pipe quickly enough and so
writing to the PTY fails.

Signed-off-by: Simon Glass <simon.glass@canonical.com>
---

 drivers/serial/sandbox.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/serial/sandbox.c b/drivers/serial/sandbox.c
index cc0491bc3c8..227524ae911 100644
--- a/drivers/serial/sandbox.c
+++ b/drivers/serial/sandbox.c
@@ -94,13 +94,16 @@  static void sandbox_print_color(struct udevice *dev)
 static int sandbox_serial_putc(struct udevice *dev, const char ch)
 {
 	struct sandbox_serial_priv *priv = dev_get_priv(dev);
+	ssize_t ret;
 
 	if (ch == '\n')
 		priv->start_of_line = true;
 
 	if (sandbox_serial_enabled) {
 		sandbox_print_color(dev);
-		os_write(1, &ch, 1);
+		ret = os_write(1, &ch, 1);
+		if (ret != 1)
+			return -EAGAIN;
 	}
 	_sandbox_serial_written += 1;
 	return 0;
@@ -120,6 +123,8 @@  static ssize_t sandbox_serial_puts(struct udevice *dev, const char *s,
 		ret = os_write(1, s, len);
 		if (ret < 0)
 			return ret;
+		if (ret != len)
+			return -EAGAIN;
 	} else {
 		ret = len;
 	}