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From:   Florian Eckert <fe@dev.tdt.de>
To:     Eckert.Florian@googlemail.com, pavel@ucw.cz, lee@kernel.org,
        kabel@kernel.org, gregkh@linuxfoundation.org,
        u.kleine-koenig@pengutronix.de
Cc:     linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [Patch v9 1/4] tty: add new helper function tty_get_tiocm
Date:   Mon, 27 Nov 2023 12:03:08 +0100
Message-ID: <20231127110311.3583957-2-fe@dev.tdt.de>
In-Reply-To: <20231127110311.3583957-1-fe@dev.tdt.de>
References: <20231127110311.3583957-1-fe@dev.tdt.de>
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There is no in-kernel function to get the status register of a tty device
like the TIOCMGET ioctl returns to userspace. Create a new function,
tty_get_tiocm(), to obtain the status register that other portions of the
kernel can call if they need this information, and move the existing
internal tty_tiocmget() function to use this interface.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
 drivers/tty/tty_io.c | 28 ++++++++++++++++++++++------
 include/linux/tty.h  |  1 +
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 06414e43e0b5..e2e93404133e 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2498,6 +2498,24 @@ static int send_break(struct tty_struct *tty, unsi=
gned int duration)
 	return retval;
 }
=20
+/**
+ * tty_get_tiocm - get tiocm status register
+ * @tty: tty device
+ *
+ * Obtain the modem status bits from the tty driver if the feature
+ * is supported.
+ */
+int tty_get_tiocm(struct tty_struct *tty)
+{
+	int retval =3D -ENOTTY;
+
+	if (tty->ops->tiocmget)
+		retval =3D tty->ops->tiocmget(tty);
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(tty_get_tiocm);
+
 /**
  * tty_tiocmget - get modem status
  * @tty: tty device
@@ -2510,14 +2528,12 @@ static int send_break(struct tty_struct *tty, uns=
igned int duration)
  */
 static int tty_tiocmget(struct tty_struct *tty, int __user *p)
 {
-	int retval =3D -ENOTTY;
+	int retval;
=20
-	if (tty->ops->tiocmget) {
-		retval =3D tty->ops->tiocmget(tty);
+	retval =3D tty_get_tiocm(tty);
+	if (retval >=3D 0)
+		retval =3D put_user(retval, p);
=20
-		if (retval >=3D 0)
-			retval =3D put_user(retval, p);
-	}
 	return retval;
 }
=20
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 4b6340ac2af2..d219a11e3fe0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -419,6 +419,7 @@ bool tty_unthrottle_safe(struct tty_struct *tty);
 int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
 int tty_get_icount(struct tty_struct *tty,
 		struct serial_icounter_struct *icount);
+int tty_get_tiocm(struct tty_struct *tty);
 int is_current_pgrp_orphaned(void);
 void tty_hangup(struct tty_struct *tty);
 void tty_vhangup(struct tty_struct *tty);
--=20
2.30.2