linux-kernel - Re: [PATCH 6/8] serial: 8250: Copy mctrl when register port.

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Date:   Wed, 6 Jun 2018 09:31:02 -0500 (CDT)
From:   Aaron Sierra <asierra@...-inc.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Matthias Brugger <mbrugger@...e.com>,
        Allen Pais <allen.lkml@...il.com>, Sean Young <sean@...s.org>,
        Ed Blake <ed.blake@...drel.com>,
        Stefan Potyra <Stefan.Potyra@...ktrobit.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Joshua Scott <joshua.scott@...iedtelesis.co.nz>,
        Vignesh R <vigneshr@...com>,
        Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>,
        Rafael Gago <rafael.gago@...il.com>,
        Joel Stanley <joel@....id.au>,
        Sean Wang <sean.wang@...iatek.com>,
        linux-serial <linux-serial@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/8] serial: 8250: Copy mctrl when register port.

----- Original Message -----
> From: "Giulio Benetti" <giulio.benetti@...ronovasrl.com>
> Sent: Friday, June 1, 2018 7:40:19 AM

> RS485 can modify mctrl on startup, especially when RTS_AFTER_SEND is on
> TIOCM_RTS is set, then need to keep it set when registering port.
> 
> Copy mctrl to new port too.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> ---
> drivers/tty/serial/8250/8250_core.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c
> b/drivers/tty/serial/8250/8250_core.c
> index c8c2b260c681..c8e62fbd6570 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -993,6 +993,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
> 		uart->port.unthrottle	= up->port.unthrottle;
> 		uart->port.rs485_config	= up->port.rs485_config;
> 		uart->port.rs485	= up->port.rs485;
> +		uart->port.mctrl	= up->port.mctrl;

Hi Guilio,

I ran into this same thing about six months ago, but I was able to
accomplish what I needed by assigning a set_mctrl() function in my
port definition. Perhaps that would be enough for your case, too?

You should see a little lower in this file that set_mctrl is copied
to the new port.

-Aaron

> 		uart->dma		= up->dma;
> 		uart->em485		= up->em485;
> 
> --
> 2.17.0