linux-kernel - Re: [Patch v8 1/6] tty: add new helper function tty_get

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Message-ID: <1b89d7df-2511-4b3e-ab35-071734fb413c@kernel.org>
Date:   Mon, 20 Nov 2023 08:21:46 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Florian Eckert <fe@....tdt.de>, Eckert.Florian@...glemail.com,
        gregkh@...uxfoundation.org, pavel@....cz, lee@...nel.org,
        kabel@...nel.org, u.kleine-koenig@...gutronix.de,
        m.brock@...mierlo.com
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [Patch v8 1/6] tty: add new helper function tty_get_tiocm

On 09. 11. 23, 9:50, Florian Eckert wrote:
> There is no in-kernel function to get the status register of a tty device
> like the TIOCMGET ioctl returns to userspace. Create a new function,
> tty_get_tiocm(), to obtain the status register that other portions of the
> kernel can call if they need this information, and move the existing
> internal tty_tiocmget() function to use this interface.
> 
> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Florian Eckert <fe@....tdt.de>
> ---
>   drivers/tty/tty_io.c | 28 ++++++++++++++++++++++------
>   include/linux/tty.h  |  1 +
>   2 files changed, 23 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 06414e43e0b5..e2e93404133e 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2498,6 +2498,24 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
>   	return retval;
>   }
>   
> +/**
> + * tty_get_tiocm - get tiocm status register
> + * @tty: tty device
> + *
> + * Obtain the modem status bits from the tty driver if the feature
> + * is supported.
> + */
> +int tty_get_tiocm(struct tty_struct *tty)
> +{
> +	int retval = -ENOTTY;
> +
> +	if (tty->ops->tiocmget)
> +		retval = tty->ops->tiocmget(tty);
> +
> +	return retval;

Why not simply:
{
  if (tty->ops->tiocmget)
     return tty->ops->tiocmget(tty);

  return -ENOTTY;
}
?

thanks,
-- 
js
suse labs