linux-kernel - Re: [PATCH] serial: set RTS and DTR if flow is 'r'

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Date:	Mon, 14 May 2007 10:54:11 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Yinghai.Lu@....COM
Cc:	Andrew Morton <akpm@...ux-foundation.org>, rmk@....linux.org.uk,
	Andi Kleen <ak@...e.de>, bjorn.helgaas@...com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: set RTS and DTR if flow is 'r'

On Mon, 14 May 2007 10:26:26 -0700 Yinghai Lu wrote:

> [PATCH] serial: set RTS and DTR if flow is 'r'
> 
> if the serial console flow is set to 'r', We need to set RTS and DTR.
> Some UARTs on other side need these bit set, otherwise will send char to or
> receive char from the host that kernel is runing esp for kernel boot stage.
> 
> BTW:
> earlyprintk and early_uart are hard coded to set DTR/RTS.
> 
> Signed-off-by: Yinghai Lu <yinghai.lu@....com>
> Cc: Russell King <rmk@....linux.org.uk>
> Cc: Andi Kleen <ak@...e.de>
> Cc: Bjorn Helgaas <bjorn.helgaas@...com>
> 
> diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
> index 48e259a..439a00a 100644
> --- a/drivers/serial/8250.c
> +++ b/drivers/serial/8250.c
> @@ -2154,6 +2154,16 @@ serial8250_set_termios(struct uart_port *port, 
> struct ktermios *termios,
> }
> serial_outp(up, UART_FCR, fcr); /* set fcr */

Something is eating tabs above and presumably in the new patch lines...

> }
> +
> + /* if serial console flow is 'r', we need to set RTS and DTR to MCR.
> + * some uarts on other side don't support no flow control. So we state
> + * console=ttyS0,9600n8r in kernel command line to make those uart can
> + * work.
> + */

/*
 * Linux long comment style is
 * like this.
 */

> + if (termios->c_cflag & CRTSCTS) {
> + up->port.mctrl |= TIOCM_RTS | TIOCM_DTR;
> + }

Don't use braces on one-statement blocks.

> +
> serial8250_set_mctrl(&up->port, up->port.mctrl);
> spin_unlock_irqrestore(&up->port.lock, flags);
> }



---
~Randy
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