linux-kernel - [PATCH 1/2] cp210x: Fix carrier handling

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Message-ID: <20091106113235.14699.13368.stgit@localhost.localdomain>
Date:	Fri, 06 Nov 2009 11:32:38 +0000
From:	Alan Cox <alan@...ux.intel.com>
To:	greg@...ah.com, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] cp210x: Fix carrier handling

9a68e39d4a701fb3be03cae9b462408664ebd205 broke carrier handling so that a
cp210x setup which needed the carrier lines set up (non CLOCAL) which did
not make a call which set the termios bits left the lines down even if
CLOCAL was not asserted.

Fix this not by reverting but by adding the proper dtr_rts and
carrier_raised methods. This both sets the modem lines properly and also
implements the correct blocking semantics for the port as required by
POSIX.

Signed-off-by: Alan Cox <alan@...ux.intel.com>
---

 drivers/usb/serial/cp210x.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)


diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 698252a..bd254ec 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -50,6 +50,8 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, struct file *,
 static void cp210x_break_ctl(struct tty_struct *, int);
 static int cp210x_startup(struct usb_serial *);
 static void cp210x_disconnect(struct usb_serial *);
+static void cp210x_dtr_rts(struct usb_serial_port *p, int on);
+static int cp210x_carrier_raised(struct usb_serial_port *p);
 
 static int debug;
 
@@ -143,6 +145,8 @@ static struct usb_serial_driver cp210x_device = {
 	.tiocmset		= cp210x_tiocmset,
 	.attach			= cp210x_startup,
 	.disconnect		= cp210x_disconnect,
+	.dtr_rts		= cp210x_dtr_rts,
+	.carrier_raised		= cp210x_carrier_raised
 };
 
 /* Config request types */
@@ -746,6 +750,14 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, struct file *file,
 	return cp210x_set_config(port, CP210X_SET_MHS, &control, 2);
 }
 
+static void cp210x_dtr_rts(struct usb_serial_port *p, int on)
+{
+	if (on)
+		cp210x_tiocmset_port(p, NULL,  TIOCM_DTR|TIOCM_RTS, 0);
+	else
+		cp210x_tiocmset_port(p, NULL,  0, TIOCM_DTR|TIOCM_RTS);
+}
+
 static int cp210x_tiocmget (struct tty_struct *tty, struct file *file)
 {
 	struct usb_serial_port *port = tty->driver_data;
@@ -768,6 +780,15 @@ static int cp210x_tiocmget (struct tty_struct *tty, struct file *file)
 	return result;
 }
 
+static int cp210x_carrier_raised(struct usb_serial_port *p)
+{
+	unsigned int control;
+	cp210x_get_config(p, CP210X_GET_MDMSTS, &control, 1);
+	if (control & CONTROL_DCD)
+		return 1;
+	return 0;
+}
+
 static void cp210x_break_ctl (struct tty_struct *tty, int break_state)
 {
 	struct usb_serial_port *port = tty->driver_data;

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