linux-kernel - Re: [PATCH v6 4/4] leds: trigger: implement a tty trigger

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Date:   Wed, 19 Feb 2020 11:52:39 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Uwe Kleine-König <uwe@...ine-koenig.org>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v6 4/4] leds: trigger: implement a tty trigger

On Thu, Feb 13, 2020 at 10:16:00AM +0100, Uwe Kleine-König wrote:
> From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> 
> Usage is as follows:
> 
> 	myled=ledname
> 	tty=ttyS0
> 
> 	echo tty > /sys/class/leds/$myled/trigger
> 	cat /sys/class/tty/$tty/dev > /sys/class/leds/$myled/dev
> 
> . When this new trigger is active it periodically checks the tty's
> statistics and when it changed since the last check the led is flashed
> once.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> ---

> +static ssize_t dev_store(struct device *dev,
> +			 struct device_attribute *attr, const char *buf,
> +			 size_t size)
> +{
> +	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
> +	struct tty_struct *tty;
> +	dev_t d;
> +	int ret;
> +
> +	if (size == 0 || (size == 1 && buf[0] == '\n')) {
> +		tty = NULL;
> +	} else {
> +		ret = kstrtodev_t(buf, &d);
> +		if (ret < 0)
> +			return ret;
> +
> +		tty = tty_kopen_shared(d);

I really don't have time to look at this, but having the led-trigger
keep the port open looks fundamentally broken (consider modem-control
signals, power, etc).

Johan