Commit bf5e5834 authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
Browse files

pl2303: Fix mode switching regression 



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: default avatarAlan Cox <alan@redhat.com>
Tested-by: default avatarMirko Parthey <mirko.parthey@informatik.tu-chemnitz.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cf059462

drivers/char/tty_ioctl.c

+19 −0
Original line number Diff line number Diff line
@@ -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

drivers/usb/serial/pl2303.c

+7 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/tty.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *);

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