[PATCH] tty: amiserial: fix broken TIOCMIWAIT

[Johan Hovold <johan@kernel.org>]

A change replacing interruptible_sleep_on() inadvertently broke the
TIOCMIWAIT implementation which now immediately returns -EIO (unless
there is a racing modem status update).

Replace the old hangup (and signal) detection with a check for the
TTY_IO_ERROR flag which is set on hangup.

Fixes: 591cee0a3563 ("tty/amiserial: avoid interruptible_sleep_on")
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/20260910132029.D80801F00898@smtp.kernel.org
Cc: stable@vger.kernel.org	# 3.14
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/tty/amiserial.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/amiserial.c b/drivers/tty/amiserial.c
index 28af0fd98181..60f6060b893d 100644
--- a/drivers/tty/amiserial.c
+++ b/drivers/tty/amiserial.c
@@ -1138,11 +1138,6 @@ static int rs_ioctl(struct tty_struct *tty,
 				local_irq_save(flags);
 				cnow = info->icount; /* atomic copy */
 				local_irq_restore(flags);
-				if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr && 
-				    cnow.dcd == cprev.dcd && cnow.cts == cprev.cts) {
-					ret = -EIO; /* no change => error */
-					break;
-				}
 				if ( ((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
 				     ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
 				     ((arg & TIOCM_CD)  && (cnow.dcd != cprev.dcd)) ||
@@ -1150,6 +1145,10 @@ static int rs_ioctl(struct tty_struct *tty,
 					ret = 0;
 					break;
 				}
+				if (tty_io_error(tty)) {
+					ret = -EIO;
+					break;
+				}
 				schedule();
 				/* see if a signal did it */
 				if (signal_pending(current)) {
-- 
2.55.0