linux-kernel - Re: [PATCH 1/2] tty: add new helper function tty_get

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Date:   Tue, 26 Sep 2023 11:48:45 +0200
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
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH 1/2] tty: add new helper function tty_get_mget

On 26. 09. 23, 11:36, Florian Eckert wrote:
> The struct 'tty_struct' has a callback to read the status flags of the tty
> if the tty driver provides them. So fare, the data is transferred directly
> to userspace with the function 'tty_tiocmget'. This function cannot be
> used to evaluate the status line of the tty interface in the ledtrig-tty
> trigger. To make this possible, a new function must be added that does
> not immediately pass the data on to userspace.
> 
> The new function 'tty_get_mget' only returns the status register.
> This information can then be processed further in the ledtrig-tty
> trigger.
> 
> Signed-off-by: Florian Eckert <fe@....tdt.de>
> ---
>   drivers/tty/tty_io.c | 29 +++++++++++++++++++++++------
>   include/linux/tty.h  |  1 +
>   2 files changed, 24 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 8a94e5a43c6d..8070ed0ce41f 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2494,6 +2494,25 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
>   	return retval;
>   }
>   
> +/**
> + * tty_get_mget		-	get modem status

Heh, the naming is funny. It apparently comes from tiocmget. But that 
comes from:
tty ioctl modem get (TIOCMGET)
tty ioctl modem set (TIOCMSET)

So you should name it like tty_get_modem() not get_mget().

Also those extra spaces around "-" caused some issues in the generated 
output and should be removed (everywhere).

> + * @tty: tty device
> + *
> + * Obtain the modem status bits from the tty driver if the feature
> + * is supported.
> + *

Superfluous empty line here.

> + */
> +int tty_get_mget(struct tty_struct *tty)
> +{
> +	int retval = -ENOTTY;
> +
> +	if (tty->ops->tiocmget)
> +		retval = tty->ops->tiocmget(tty);
> +
> +	return retval;
> +}
> +EXPORT_SYMBOL_GPL(tty_get_mget);


thanks,
-- 
js
suse labs