> applied in reverse (a partial revert to 2.6.22) makes
> the corruption go away, but is likely just papering over the root cause.
> Cc'ed the gpsbabel developer mailing list, in case we have to
> fix this in userspace.

Please try the following

diff -u --new-file --recursive --exclude-from /usr/src/exclude 
linux.vanilla-2.6.24-rc6-mm1/drivers/usb/serial/pl2303.c 
linux-2.6.24-rc6-mm1/drivers/usb/serial/pl2303.c
--- linux.vanilla-2.6.24-rc6-mm1/drivers/usb/serial/pl2303.c    2008-01-02 
16:04:24.000000000 +0000
+++ linux-2.6.24-rc6-mm1/drivers/usb/serial/pl2303.c    2008-01-07 
11:47:59.000000000 +0000
@@ -531,6 +531,13 @@
        }
        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 -u --new-file --recursive --exclude-from /usr/src/exclude 
linux.vanilla-2.6.24-rc6-mm1/drivers/char/tty_ioctl.c 
linux-2.6.24-rc6-mm1/drivers/char/tty_ioctl.c
--- linux.vanilla-2.6.24-rc6-mm1/drivers/char/tty_ioctl.c       2008-01-02 
16:04:19.000000000 +0000
+++ linux-2.6.24-rc6-mm1/drivers/char/tty_ioctl.c       2008-01-07 
11:43:39.000000000 +0000
@@ -360,6 +360,25 @@
 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
  *     @new_termios: desired new value
diff -u --new-file --recursive --exclude-from /usr/src/exclude 
linux.vanilla-2.6.24-rc6-mm1/include/linux/tty.h 
linux-2.6.24-rc6-mm1/include/linux/tty.h
--- linux.vanilla-2.6.24-rc6-mm1/include/linux/tty.h    2008-01-02 
16:04:25.000000000 +0000
+++ linux-2.6.24-rc6-mm1/include/linux/tty.h    2008-01-07 11:43:19.000000000 
+0000
@@ -312,6 +312,7 @@
 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 *);
-
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