Messages in this thread Patch in this message | | | Date | Tue, 8 Jan 2008 14:55:51 +0000 | From | Alan Cox <> | Subject | [PATCH] pl2303: Fix mode switching regression |
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Cleaning out all the incorrect 'no change made' checks for termios settings showed up a problem with the PL2303. The hardware here seems to lose sync and bits if you tell it to make no changes. This shows up with a real world application.
To fix this the driver check for meaningful hardware changes is restored but doing the tests correctly and as a tty layer function so it doesn't get duplicated wrongly everywhere if other drivers turn out to need it.
Signed-off-by: Alan Cox <alan@redhat.com> Tested-by: Mirko Parthey <mirko.parthey@informatik.tu-chemnitz.de>
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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