FAILED: patch "[PATCH] Bluetooth: rfcomm: fix modem control handling" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] Bluetooth: rfcomm: fix modem control handling" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 91d35ec9b3956d6b3cf789c1593467e58855b03a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025110248-creative-police-9150@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 91d35ec9b3956d6b3cf789c1593467e58855b03a Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Thu, 23 Oct 2025 14:05:30 +0200
Subject: [PATCH] Bluetooth: rfcomm: fix modem control handling

The RFCOMM driver confuses the local and remote modem control signals,
which specifically means that the reported DTR and RTS state will
instead reflect the remote end (i.e. DSR and CTS).

This issue dates back to the original driver (and a follow-on update)
merged in 2002, which resulted in a non-standard implementation of
TIOCMSET that allowed controlling also the TS07.10 IC and DV signals by
mapping them to the RI and DCD input flags, while TIOCMGET failed to
return the actual state of DTR and RTS.

Note that the bogus control of input signals in tiocmset() is just
dead code as those flags will have been masked out by the tty layer
since 2003.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 376ce6de84be..b783526ab588 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -643,8 +643,8 @@ static void rfcomm_dev_modem_status(struct rfcomm_dlc *dlc, u8 v24_sig)
 		tty_port_tty_hangup(&dev->port, true);
 
 	dev->modem_status =
-		((v24_sig & RFCOMM_V24_RTC) ? (TIOCM_DSR | TIOCM_DTR) : 0) |
-		((v24_sig & RFCOMM_V24_RTR) ? (TIOCM_RTS | TIOCM_CTS) : 0) |
+		((v24_sig & RFCOMM_V24_RTC) ? TIOCM_DSR : 0) |
+		((v24_sig & RFCOMM_V24_RTR) ? TIOCM_CTS : 0) |
 		((v24_sig & RFCOMM_V24_IC)  ? TIOCM_RI : 0) |
 		((v24_sig & RFCOMM_V24_DV)  ? TIOCM_CD : 0);
 }
@@ -1055,10 +1055,14 @@ static void rfcomm_tty_hangup(struct tty_struct *tty)
 static int rfcomm_tty_tiocmget(struct tty_struct *tty)
 {
 	struct rfcomm_dev *dev = tty->driver_data;
+	struct rfcomm_dlc *dlc = dev->dlc;
+	u8 v24_sig;
 
 	BT_DBG("tty %p dev %p", tty, dev);
 
-	return dev->modem_status;
+	rfcomm_dlc_get_modem_status(dlc, &v24_sig);
+
+	return (v24_sig & (TIOCM_DTR | TIOCM_RTS)) | dev->modem_status;
 }
 
 static int rfcomm_tty_tiocmset(struct tty_struct *tty, unsigned int set, unsigned int clear)
@@ -1071,23 +1075,15 @@ static int rfcomm_tty_tiocmset(struct tty_struct *tty, unsigned int set, unsigne
 
 	rfcomm_dlc_get_modem_status(dlc, &v24_sig);
 
-	if (set & TIOCM_DSR || set & TIOCM_DTR)
+	if (set & TIOCM_DTR)
 		v24_sig |= RFCOMM_V24_RTC;
-	if (set & TIOCM_RTS || set & TIOCM_CTS)
+	if (set & TIOCM_RTS)
 		v24_sig |= RFCOMM_V24_RTR;
-	if (set & TIOCM_RI)
-		v24_sig |= RFCOMM_V24_IC;
-	if (set & TIOCM_CD)
-		v24_sig |= RFCOMM_V24_DV;
 
-	if (clear & TIOCM_DSR || clear & TIOCM_DTR)
+	if (clear & TIOCM_DTR)
 		v24_sig &= ~RFCOMM_V24_RTC;
-	if (clear & TIOCM_RTS || clear & TIOCM_CTS)
+	if (clear & TIOCM_RTS)
 		v24_sig &= ~RFCOMM_V24_RTR;
-	if (clear & TIOCM_RI)
-		v24_sig &= ~RFCOMM_V24_IC;
-	if (clear & TIOCM_CD)
-		v24_sig &= ~RFCOMM_V24_DV;
 
 	rfcomm_dlc_set_modem_status(dlc, v24_sig);