From: Pho Tran <Pho.Tran@silabs.com>
To: "johan@kernel.org" <johan@kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
Hung Nguyen <Hung.Nguyen@silabs.com>
Subject: [PATCH v3] USB: serial: cp210x: Fix error 32 when hardware flow control is enabled.
Date: Thu, 21 Jan 2021 07:09:13 +0000 [thread overview]
Message-ID: <9E531B87-06A8-45F0-A2A8-EC6FA61A99A7@silabs.com> (raw)
Fix error 32 returned by CP210X_SET_MHS when hardware flow control is enabled.
The root cause of error 32 is that user application (CoolTerm, linux-serial-test)
opened cp210x device with hardware flow control then attempt to control RTS/DTR pins.
In hardware flow control, RTS/DTR pins will be controlled by hardware only,
any attempt to control those pins will cause error 32 from the device.
This fix will block MHS command(command to control RTS/DTR pins) to the device
if hardware flow control is being used.
Signed-off-by: Pho Tran <pho.tran@silabs.com>
---
01/19/2021: Patch v2 Modified based on comment from Johan Hovold <johan@kernel.org>
and Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/serial/cp210x.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index fbb10dfc56e3..5b6bbda2b424 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1204,7 +1204,12 @@ static int cp210x_tiocmset(struct tty_struct *tty,
unsigned int set, unsigned int clear)
{
struct usb_serial_port *port = tty->driver_data;
- return cp210x_tiocmset_port(port, set, clear);
+ if (C_CRTSCTS(tty))
+
+ /* Don't send SET_MHS command if device in hardware flow control mode. */
+ return 0;
+ else
+ return cp210x_tiocmset_port(port, set, clear);
}
static int cp210x_tiocmset_port(struct usb_serial_port *port,
--
2.17.1
next reply other threads:[~2021-01-21 7:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 7:09 Pho Tran [this message]
2021-01-21 7:39 ` [PATCH v3] USB: serial: cp210x: Fix error 32 when hardware flow control is enabled gregkh
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