[PATCH 2/8] USB: serial: kobil_sct: fix TIOCMBIS and TIOCMBIC

Johan Hovold
2025-10-22T15:26:54Z

Asserting or deasserting a modem control line using TIOCMBIS or TIOCMBIC
should not deassert any lines that are not in the mask.

Fix this long-standing issue dating back to 2003 when the support for
these ioctls was added with the introduction of the tiocmset() callback.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/serial/kobil_sct.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/serial/kobil_sct.c b/drivers/usb/serial/kobil_sct.c
index 464433be2034..96ea571c436a 100644
--- a/drivers/usb/serial/kobil_sct.c
+++ b/drivers/usb/serial/kobil_sct.c
@@ -418,7 +418,7 @@ static int kobil_tiocmset(struct tty_struct *tty,
struct usb_serial_port *port = tty->driver_data;
struct device *dev = &port->dev;
struct kobil_private *priv;
- int result;
+ int result = 0;
int dtr = 0;
int rts = 0;

@@ -435,12 +435,12 @@ static int kobil_tiocmset(struct tty_struct *tty,
if (set & TIOCM_DTR)
dtr = 1;
if (clear & TIOCM_RTS)
- rts = 0;
+ rts = 1;
if (clear & TIOCM_DTR)
- dtr = 0;
+ dtr = 1;

- if (priv->device_type == KOBIL_ADAPTER_B_PRODUCT_ID) {
- if (dtr != 0)
+ if (dtr && priv->device_type == KOBIL_ADAPTER_B_PRODUCT_ID) {
+ if (set & TIOCM_DTR)
dev_dbg(dev, "%s - Setting DTR\n", __func__);
else
dev_dbg(dev, "%s - Clearing DTR\n", __func__);
@@ -448,13 +448,13 @@ static int kobil_tiocmset(struct tty_struct *tty,
usb_sndctrlpipe(port->serial->dev, 0),
SUSBCRequest_SetStatusLinesOrQueues,
USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_OUT,
- ((dtr != 0) ? SUSBCR_SSL_SETDTR : SUSBCR_SSL_CLRDTR),
+ ((set & TIOCM_DTR) ? SUSBCR_SSL_SETDTR : SUSBCR_SSL_CLRDTR),
0,
NULL,
0,
KOBIL_TIMEOUT);
- } else {
- if (rts != 0)
+ } else if (rts) {
+ if (set & TIOCM_RTS)
dev_dbg(dev, "%s - Setting RTS\n", __func__);
else
dev_dbg(dev, "%s - Clearing RTS\n", __func__);
@@ -462,7 +462,7 @@ static int kobil_tiocmset(struct tty_struct *tty,
usb_sndctrlpipe(port->serial->dev, 0),
SUSBCRequest_SetStatusLinesOrQueues,
USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_OUT,
- ((rts != 0) ? SUSBCR_SSL_SETRTS : SUSBCR_SSL_CLRRTS),
+ ((set & TIOCM_RTS) ? SUSBCR_SSL_SETRTS : SUSBCR_SSL_CLRRTS),
0,
NULL,
0,
--
2.49.1