On Wed, Feb 13, 2013 at 08:11:13PM -0500, Peter Hurley wrote:
> 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().
Yeah, I mentioned both of these points in the cover letter of the
series. From a quick browse it seemed that I would have to fix n_gsm.c
and mxser.c, but I'll have a closer look at this later.
Thanks,
Johan
> 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
>
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