Bluetooth: rfcomm: fix modem control handling

PATCH Superseded Johan Hovold 2 participants 2 messages Oct 23, 2025

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Stable branch Bluetooth drivers Bluetooth

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Johan Hovold

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2025-10-23 12:02 UTC #0 lore raw

PATCH 1/1 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 [email protected]

Signed-off-by Johan Hovold <[email protected]>

---
 net/bluetooth/rfcomm/tty.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

net/bluetooth/rfcomm/tty.c +10 ~~-15~~

index 376ce6de84be..f20f043cc9b5 100644
@@ -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 +1055,13 @@ 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;
+	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 +1074,15 @@ 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);

Signature · 1 line

2.49.1

[email protected]

2025-10-23 12:50 UTC #1 lore raw

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list. This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=1014979

---Test result---

Test Summary:

CheckPatch                    PENDING   0.38 seconds
GitLint                       PENDING   0.28 seconds
SubjectPrefix                 PASS      0.08 seconds
BuildKernel                   FAIL      17.72 seconds
CheckAllWarning               FAIL      19.38 seconds
CheckSparse                   FAIL      21.16 seconds
BuildKernel32                 FAIL      16.88 seconds
TestRunnerSetup               PASS      488.31 seconds
TestRunner_l2cap-tester       PASS      23.91 seconds
TestRunner_iso-tester         FAIL      60.16 seconds
TestRunner_bnep-tester        PASS      6.34 seconds
TestRunner_mgmt-tester        FAIL      125.50 seconds
TestRunner_rfcomm-tester      PASS      9.36 seconds
TestRunner_sco-tester         PASS      14.47 seconds
TestRunner_ioctl-tester       PASS      10.09 seconds
TestRunner_mesh-tester        FAIL      11.36 seconds
TestRunner_smp-tester         PASS      8.45 seconds
TestRunner_userchan-tester    PASS      6.38 seconds
IncrementalBuild              PENDING   1.07 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: BuildKernel - FAIL
Desc: Build Kernel for Bluetooth
Output:

net/bluetooth/rfcomm/tty.c: In function ‘rfcomm_tty_tiocmget’:
net/bluetooth/rfcomm/tty.c:1062:30: error: ‘dlc’ undeclared (first use in this function)
1062 | rfcomm_dlc_get_modem_status(dlc, &v24_sig);
| ^~~
net/bluetooth/rfcomm/tty.c:1062:30: note: each undeclared identifier is reported only once for each function it appears in make[5]: *** [scripts/Makefile.build:287: net/bluetooth/rfcomm/tty.o] Error 1
make[4]: *** [scripts/Makefile.build:556: net/bluetooth/rfcomm] Error 2
make[4]: *** Waiting for unfinished jobs....
net/bluetooth/af_bluetooth.c:248:25: warning: context imbalance in 'bt_accept_enqueue' - different lock contexts for basic block make[3]: *** [scripts/Makefile.build:556: net/bluetooth] Error 2
make[2]: *** [scripts/Makefile.build:556: net] Error 2
make[2]: *** Waiting for unfinished jobs....
drivers/bluetooth/hci_ag6xx.c:257:24: warning: restricted __le32 degrades to integer drivers/bluetooth/hci_mrvl.c:170:23: warning: restricted __le16 degrades to integer drivers/bluetooth/hci_mrvl.c:203:23: warning: restricted __le16 degrades to integer drivers/bluetooth/hci_nokia.c:279:23: warning: incorrect type in assignment (different base types)
drivers/bluetooth/hci_nokia.c:279:23: expected unsigned short [usertype] baud
drivers/bluetooth/hci_nokia.c:279:23: got restricted __le16 [usertype]
drivers/bluetooth/hci_nokia.c:282:26: warning: incorrect type in assignment (different base types)
drivers/bluetooth/hci_nokia.c:282:26: expected unsigned short [usertype] sys_clk
drivers/bluetooth/hci_nokia.c:282:26: got restricted __le16 [usertype]
make[1]: *** [/github/workspace/src/src/Makefile:2011: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2
##############################
Test: BuildKernel32 - FAIL
Desc: Build 32bit Kernel for Bluetooth
Output:

Failed Test Cases

Read Exp Feature - Success                           Failed       0.105 seconds
LL Privacy - Add Device 2 (2 Devices to AL)          Failed       0.182 seconds
LL Privacy - Set Flags 2 (Enable RL)                 Failed       0.154 seconds

##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases

Mesh - Send cancel - 1                               Timed out    1.878 seconds
Mesh - Send cancel - 2                               Timed out    1.996 seconds

##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series Output:

---
Regards,
Linux Bluetooth