linux-kernel - Re: [PATCH 16/16] s390/char/con3270: use tty_port

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Message-ID: <20250814081948.7684Af9-hca@linux.ibm.com>
Date: Thu, 14 Aug 2025 10:19:48 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Cc: gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org
Subject: Re: [PATCH 16/16] s390/char/con3270: use tty_port_tty guard()

On Thu, Aug 14, 2025 at 09:24:56AM +0200, Jiri Slaby (SUSE) wrote:
> Having the new tty_port_tty guard, use it in tty3270_resize(). This
> makes the code easier to read. The winsize is now defined in the
> scope and initialized immediately, so that it's obvious.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
> Cc: Sven Schnelle <svens@...ux.ibm.com>
> ---
> Cc: linux-s390@...r.kernel.org
> ---
>  drivers/s390/char/con3270.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)

...

> -	tty = tty_port_tty_get(&tp->port);
> -	if (!tty)
> -		return;
> -	ws.ws_row = tty3270_tty_rows(tp);
> -	ws.ws_col = tp->view.cols;
> -	tty_do_resize(tty, &ws);
> -	tty_kref_put(tty);
> +	/* Inform the tty layer about new size */
> +	scoped_guard(tty_port_tty, &tp->port) {
> +		struct winsize ws = {
> +			.ws_row = tty3270_tty_rows(tp),
> +			.ws_col = tp->view.cols,
> +		};
> +		tty_do_resize(scoped_tty(), &ws);
> +	}

This generates worse code compared to before, since an extra not needed
"if (IS_ERR(...))" check is added implicitly. For this particular code
it doesn't matter.
Just wanted to mention it, since this is not stated anywhere.

In any case:
Acked-by: Heiko Carstens <hca@...ux.ibm.com>