From a0322415e9bc928528a1ede966846814ec2e81c1 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: Tue, 8 Jan 2008 14:55:51 +0000
Subject: [PATCH] --- yaml --- r: 75310 b: refs/heads/master c:
 bf5e5834bffc62b50cd4a201804506eb11ef1af8 h: refs/heads/master v: v3

---
 [refs]                            |  2 +-
 trunk/drivers/char/tty_ioctl.c    | 19 +++++++++++++++++++
 trunk/drivers/usb/serial/pl2303.c |  7 +++++++
 trunk/include/linux/tty.h         |  1 +
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 9108390d8a26..9064b3513bff 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: cf0594625083111ae522496dc1c256f7476939c2
+refs/heads/master: bf5e5834bffc62b50cd4a201804506eb11ef1af8
diff --git a/trunk/drivers/char/tty_ioctl.c b/trunk/drivers/char/tty_ioctl.c
index e02d59245a17..d4b6d64e858b 100644
--- a/trunk/drivers/char/tty_ioctl.c
+++ b/trunk/drivers/char/tty_ioctl.c
@@ -364,6 +364,25 @@ void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
 
 EXPORT_SYMBOL(tty_termios_copy_hw);
 
+/**
+ *	tty_termios_hw_change	-	check for setting change
+ *	@a: termios
+ *	@b: termios to compare
+ *
+ *	Check if any of the bits that affect a dumb device have changed
+ *	between the two termios structures, or a speed change is needed.
+ */
+
+int tty_termios_hw_change(struct ktermios *a, struct ktermios *b)
+{
+	if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
+		return 1;
+	if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
+		return 1;
+	return 0;
+}
+EXPORT_SYMBOL(tty_termios_hw_change);
+
 /**
  *	change_termios		-	update termios values
  *	@tty: tty to update
diff --git a/trunk/drivers/usb/serial/pl2303.c b/trunk/drivers/usb/serial/pl2303.c
index cf8add91de05..0da1df9c79bf 100644
--- a/trunk/drivers/usb/serial/pl2303.c
+++ b/trunk/drivers/usb/serial/pl2303.c
@@ -483,6 +483,13 @@ static void pl2303_set_termios(struct usb_serial_port *port,
 	}
 	spin_unlock_irqrestore(&priv->lock, flags);
 
+	/* The PL2303 is reported to lose bytes if you change
+	   serial settings even to the same values as before. Thus
+	   we actually need to filter in this specific case */
+
+	if (!tty_termios_hw_change(port->tty->termios, old_termios))
+		return;
+
 	cflag = port->tty->termios->c_cflag;
 
 	buf = kzalloc(7, GFP_KERNEL);
diff --git a/trunk/include/linux/tty.h b/trunk/include/linux/tty.h
index c555f5442bd7..defd2ab72449 100644
--- a/trunk/include/linux/tty.h
+++ b/trunk/include/linux/tty.h
@@ -319,6 +319,7 @@ extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);
 extern void tty_termios_encode_baud_rate(struct ktermios *termios, speed_t ibaud, speed_t obaud);
 extern void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud);
 extern void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old);
+extern int tty_termios_hw_change(struct ktermios *a, struct ktermios *b);
 
 extern struct tty_ldisc *tty_ldisc_ref(struct tty_struct *);
 extern void tty_ldisc_deref(struct tty_ldisc *);