linux-kernel - [156/200] USB: ftdi_sio: fix DTR/RTS line modes

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Date:	Thu, 01 Jul 2010 10:44:06 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Daniel Mack <daniel@...aq.de>,
	Johan Hovold <jhovold@...il.com>,
	Alan Cox <alan@...ux.intel.com>
Subject: [156/200] USB: ftdi_sio: fix DTR/RTS line modes

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Mack <daniel@...aq.de>

commit 6a1a82df91fa0eb1cc76069a9efe5714d087eccd upstream.

Call set_mctrl() and clear_mctrl() according to the flow control mode
selected. This makes serial communication for FT232 connected devices
work when CRTSCTS is not set.

This fixes a regression introduced by 4175f3e31 ("tty_port: If we are
opened non blocking we still need to raise the carrier"). This patch
calls the low-level driver's dtr_rts() function which consequently sets
TIOCM_DTR | TIOCM_RTS. A later call to set_termios() without CRTSCTS in
cflags, however, does not reset these bits, and so data is not actually
sent out on the serial wire.

Signed-off-by: Daniel Mack <daniel@...aq.de>
Cc: Johan Hovold <jhovold@...il.com>
Cc: Alan Cox <alan@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/usb/serial/ftdi_sio.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2289,6 +2289,8 @@ static void ftdi_set_termios(struct tty_
 				"urb failed to set to rts/cts flow control\n");
 		}
 
+		/* raise DTR/RTS */
+		set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
 	} else {
 		/*
 		 * Xon/Xoff code
@@ -2336,6 +2338,8 @@ static void ftdi_set_termios(struct tty_
 			}
 		}
 
+		/* lower DTR/RTS */
+		clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
 	}
 	return;
 }


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