linux-kernel - Re: [PATCH] tty_ioctl: Soft carrier handling

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Date:	Mon, 10 Mar 2008 23:24:04 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty_ioctl: Soft carrier handling

On 03/10/2008 10:56 PM, Alan Cox wrote:
> First cut at moving the soft carrier handling knowledge entirely into the
> core code. One or two drivers still needed to snoop these functions to
> track CLOCAL internally. Instead make TIOCSSOFTCAR generate the same
> driver calls as other termios ioctls changing the clocal flag. This
> allows us to remove any driver knowledge and special casing. Also while
> we are at it we can fix the error handling.
> 
> Signed-off-by: Alan Cox <alan@...hat.com>
> 
> diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.25-rc3-mm1/drivers/char/tty_ioctl.c linux-2.6.25-rc3-mm1/drivers/char/tty_ioctl.c
> --- linux.vanilla-2.6.25-rc3-mm1/drivers/char/tty_ioctl.c	2008-03-10 12:57:53.000000000 +0000
> +++ linux-2.6.25-rc3-mm1/drivers/char/tty_ioctl.c	2008-03-10 13:27:09.000000000 +0000
> @@ -753,6 +756,32 @@
[...]
> +static int tty_change_softcar(struct tty_struct *tty, int arg)
> +{
> +	int ret = 0;
> +	int bit = arg ? CLOCAL : 0;
> +	struct ktermios old = *tty->termios;

Maybe a dumb question, but shouldn't be the snapshot done in the critical 
section too?

> +	
> +	mutex_lock(&tty->termios_mutex);
> +	tty->termios->c_cflag &= ~CLOCAL;
> +	tty->termios->c_cflag |= bit;
> +	if (tty->driver->set_termios)
> +		tty->driver->set_termios(tty, &old);
> +	if ((tty->termios->c_cflag & CLOCAL) != bit)
> +		ret = -EINVAL;	
> +	mutex_unlock(&tty->termios_mutex);
> +	return ret;
> +}
--
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