From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [RFC 2/4] tty: fix DTR/RTS not being dropped on hang up Date: Wed, 13 Feb 2013 20:11:13 -0500 Message-ID: <1360804273.3385.23.camel@thor.lan> References: <20130213142513.GA21078@localhost> <1360776446-31371-1-git-send-email-jhovold@gmail.com> <1360776446-31371-3-git-send-email-jhovold@gmail.com> <1360783973.8499.48.camel@thor.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1360783973.8499.48.camel-AsKIXgLx6sE@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Johan Hovold Cc: Greg KH , Chris Ruehl , Alan Stern , Alan Cox , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alan Cox List-Id: linux-serial@vger.kernel.org On Wed, 2013-02-13 at 14:32 -0500, Peter Hurley wrote: > On Wed, 2013-02-13 at 18:27 +0100, Johan Hovold wrote: > > Move HUPCL handling to port shutdown so that DTR/RTS is dropped also on > > hang up. > > > > Currently a hung up port will return immediately from > > tty_port_close_start leaving DTR/RTS unchanged. > > --- > > drivers/tty/tty_port.c | 22 ++++++++++++---------- > > 1 file changed, 12 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c > > index 57a061e..ffe3689 100644 > > --- a/drivers/tty/tty_port.c > > +++ b/drivers/tty/tty_port.c > > @@ -198,11 +198,20 @@ EXPORT_SYMBOL(tty_port_tty_set); > > > > static void tty_port_shutdown(struct tty_port *port) > > { > > + struct tty_struct *tty = port->tty; > > + > > mutex_lock(&port->mutex); > > if (port->console) > > goto out; > > > > if (test_and_clear_bit(ASYNCB_INITIALIZED, &port->flags)) { > > + /* > > + * Drop DTR/RTS if HUPCL is set. This causes any attached > > + * modem to hang up the line. > > + */ > > + if (!tty || tty->termios.c_cflag & HUPCL) > > + tty_port_lower_dtr_rts(port); > > + > > port->ops->shutdown() requires the hardware to reset anyway, including > the DTR/RTS state. Ok, after reviewing this further, I like this more. For one, there is more flexibility for tty drivers that have a custom close() routine (ie, one that doesn't call tty_port_close()). At the same time, every call site of tty_port_close_start() needs to be checked to ensure it does not assume (or does not require) DTR to be dropped: char/pcmcia/synclink_cs.c: if (tty_port_close_start(port, tty, filp) == 0) tty/synclinkmp.c: if (tty_port_close_start(&info->port, tty, filp) == 0) tty/rocket.c: if (tty_port_close_start(port, tty, filp) == 0) tty/amiserial.c: if (tty_port_close_start(port, tty, filp) == 0) tty/n_gsm.c: if (tty_port_close_start(&dlci->port, tty, filp) == 0) tty/mxser.c: if (tty_port_close_start(port, tty, filp) == 0) tty/synclink_gt.c: if (tty_port_close_start(&info->port, tty, filp) == 0) tty/serial/serial_core.c: if (tty_port_close_start(port, tty, filp) == 0) tty/synclink.c: if (tty_port_close_start(&info->port, tty, filp) == 0) In the case of the serial core, this actually fixes the code excerpt below where tty_port_close_start() prematurely drops DTR before the uart can stop_rx() or wait_until_sent(). static void uart_close(struct tty_struct *tty, struct file *filp) { struct uart_state *state = tty->driver_data; struct tty_port *port; struct uart_port *uport; unsigned long flags; if (!state) return; uport = state->uart_port; port = &state->port; pr_debug("uart_close(%d) called\n", uport->line); if (tty_port_close_start(port, tty, filp) == 0) return; /* * At this point, we stop accepting input. To do this, we * disable the receive line status interrupts. */ if (port->flags & ASYNC_INITIALIZED) { unsigned long flags; spin_lock_irqsave(&uport->lock, flags); uport->ops->stop_rx(uport); spin_unlock_irqrestore(&uport->lock, flags); /* * Before we drop DTR, make sure the UART transmitter * has completely drained; this is especially * important if there is a transmit FIFO! */ uart_wait_until_sent(tty, uport->timeout); } mutex_lock(&port->mutex); uart_shutdown(tty, state); uart_flush_buffer(tty); Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html