linux-kernel - Re: [patch 1/1] staging: speakup: flush tty buffers and ensure hardware flow control

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Date:   Wed, 10 May 2017 20:41:51 +0100
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     okash.khawaja@...il.com
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Samuel Thibault <samuel.thibault@...-lyon.org>,
        linux-kernel@...r.kernel.org, William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org, John Covici <covici@....covici.com>
Subject: Re: [patch 1/1] staging: speakup: flush tty buffers and ensure
 hardware flow control

> +	if (!(tmp_termios.c_cflag & CRTSCTS)) {
> +		tmp_termios.c_cflag |= CRTSCTS;
> +		ret = tty_set_termios(tty, &tmp_termios);
> +		if (ret)
> +			pr_warn("speakup: Failed to set hardware flow control\n");

You should check the tty c_cflag after the call rather than rely on an
error code. Strictly speaking tty_set_termios should error if no tty bits
are changed by the request but it never has on Linux. Instead check the
tty gave you the result you wanted.

Alan