linux-kernel - Re: [PATCH 2/4] serial: 8250: Copy mctrl when register port.

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Date:   Wed, 06 Jun 2018 15:01:05 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     matwey.kornilov@...il.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Allen Pais <allen.lkml@...il.com>, Sean Young <sean@...s.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] serial: 8250: Copy mctrl when register port.

On Wed, 2018-06-06 at 11:49 +0200, Giulio Benetti wrote:
> 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.
> 

Not sure if it would be useful.
Seems the only em485 user, i.e. OMAP, does survive without that.

Moreover, often individual drivers override ->set_mctrl() callback.

So, real example is needed to explain why.

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

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy