linux-kernel - Re: should RTS init in serial core be tied to CRTSCTS

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Message-ID: <m3bqj6jebt.fsf@maximus.localdomain>
Date:	Tue, 06 Mar 2007 21:40:22 +0100
From:	Krzysztof Halasa <khc@...waw.pl>
To:	"Mike Frysinger" <vapier.adi@...il.com>
Cc:	rmk@....linux.org.uk,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org,
	"Robin Getz" <rgetz@...ckfin.uclinux.org>
Subject: Re: should RTS init in serial core be tied to CRTSCTS

"Mike Frysinger" <vapier.adi@...il.com> writes:

>            /*
>             * Setup the RTS and DTR signals once the
>             * port is open and ready to respond.
>             */
>            if (info->tty->termios->c_cflag & CBAUD)
>                uart_set_mctrl(port, TIOCM_RTS | TIOCM_DTR);
> ...
>
> shouldnt TIOCM_RTS be passed down only when the 'r' is appended to the
> boot cmdline ?

How would it be useful?

CRTSCTS is for CTS only (i.e., the transmission is paused when CTS is
inactive), not for RTS. DTR and RTS should be active when the port is
open even without CRTSCTS (= without handshaking), it's used for
various purposes such as providing +12V to the device (and two pins
can supply more power than one - sure, it isn't the best idea).

I wouldn't touch that.
-- 
Krzysztof Halasa
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