linux-kernel - Re: [PATCH v2 2/6] can: slcan: remove legacy infrastructure

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Message-ID: <20220725123804.ofqpq4j467qkbtzn@pengutronix.de>
Date:   Mon, 25 Jul 2022 14:38:04 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org, michael@...rulasolutions.com,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Jeroen Hofstee <jhofstee@...tronenergy.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Max Staudt <max@...as.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 2/6] can: slcan: remove legacy infrastructure

On 25.07.2022 08:54:15, Dario Binacchi wrote:
> Taking inspiration from the drivers/net/can/can327.c driver and at the
> suggestion of its author Max Staudt, I removed legacy stuff like
> `SLCAN_MAGIC' and `slcan_devs' resulting in simplification of the code
> and its maintainability.
> 
> The use of slcan_devs is derived from a very old kernel, since slip.c
> is about 30 years old, so today's kernel allows us to remove it.
> 
> The .hangup() ldisc function, which only called the ldisc .close(), has
> been removed since the ldisc layer calls .close() in a good place
> anyway.
> 
> The old slcanX name has been dropped in order to use the standard canX
> interface naming. It has been assumed that this change does not break
> the user space as the slcan driver provides an ioctl to resolve from tty
> fd to netdev name.

Is there a man page that documents this iotcl? Please add it and/or the
IOCTL name.

> The `maxdev' module parameter has also been removed.
> 
> CC: Max Staudt <max@...as.org>
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> 
> ---
> 
> Changes in v2:

Nitpick:
Changes since RFC: https://lore.kernel.org/all/20220716170007.2020037-1-dario.binacchi@amarulasolutions.com

> - Update the commit description.
> - Drop the old "slcan" name to use the standard canX interface naming.
> 
>  drivers/net/can/slcan/slcan-core.c | 318 ++++++-----------------------
>  1 file changed, 63 insertions(+), 255 deletions(-)
> 
> diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
> index c3dd7468a066..2c546f4a7981 100644
> --- a/drivers/net/can/slcan/slcan-core.c
> +++ b/drivers/net/can/slcan/slcan-core.c

[...]

> @@ -898,72 +799,49 @@ static int slcan_open(struct tty_struct *tty)
>  	if (!tty->ops->write)
>  		return -EOPNOTSUPP;
>  
> -	/* RTnetlink lock is misused here to serialize concurrent
> -	 * opens of slcan channels. There are better ways, but it is
> -	 * the simplest one.
> -	 */
> -	rtnl_lock();
> +	dev = alloc_candev(sizeof(*sl), 1);
> +	if (!dev)
> +		return -ENFILE;
>  
> -	/* Collect hanged up channels. */
> -	slc_sync();
> +	sl = netdev_priv(dev);
>  
> -	sl = tty->disc_data;
> +	/* Configure TTY interface */
> +	tty->receive_room = 65536; /* We don't flow control */
> +	sl->rcount   = 0;
> +	sl->xleft    = 0;

Nitpick: Please use 1 space in front of the =.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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