From: Johan Hovold <johan@kernel.org>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Johan Hovold <johan@kernel.org>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
Pavel Machek <pavel@ucw.cz>, Dan Murphy <dmurphy@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel@pengutronix.de, linux-serial@vger.kernel.org
Subject: Re: [PATCH v6 4/4] leds: trigger: implement a tty trigger
Date: Wed, 19 Feb 2020 12:19:13 +0100 [thread overview]
Message-ID: <20200219111913.GB32540@localhost> (raw)
In-Reply-To: <20200219110306.k5jndutalll64esu@pengutronix.de>
On Wed, Feb 19, 2020 at 12:03:06PM +0100, Uwe Kleine-König wrote:
> On Wed, Feb 19, 2020 at 11:52:39AM +0100, Johan Hovold wrote:
> > On Thu, Feb 13, 2020 at 10:16:00AM +0100, Uwe Kleine-König wrote:
> > > From: Uwe Kleine-König <u.kleine-koenig@pengutronix.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@pengutronix.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).
>
> If I understand correctly calling tty_kopen_shared() doesn't open the
> device, just keep it referenced which prevents it to disappear. Unless I
> miss something it doesn't result in the tty's .open() being called.
So tty_kopen_shared() is something you added. Judging from a quick look
it seems you can only attach a trigger to an already open port, but the
trigger will then keep the port open (again, consider modem control,
power).
I'm sorry I don't have time to review this myself, but this probably
needs some more eyes on it before being merged.
Johan
next prev parent reply other threads:[~2020-02-19 11:19 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 9:15 [PATCH v6 0/4] leds: trigger: implement a tty trigger Uwe Kleine-König
2020-02-13 9:15 ` [PATCH v6 1/4] lib: new helper kstrtodev_t() Uwe Kleine-König
2020-02-19 19:50 ` Andy Shevchenko
2020-02-20 7:49 ` Uwe Kleine-König
2020-02-20 10:22 ` Andy Shevchenko
2020-02-20 10:57 ` Uwe Kleine-König
2020-02-20 11:46 ` Andy Shevchenko
2020-02-20 11:57 ` Andy Shevchenko
2020-02-20 14:01 ` Uwe Kleine-König
2020-02-21 8:42 ` Andy Shevchenko
2020-02-21 10:53 ` Uwe Kleine-König
2020-04-25 7:07 ` Pavel Machek
2020-02-13 9:15 ` [PATCH v6 2/4] tty: rename tty_kopen() and add new function tty_kopen_shared() Uwe Kleine-König
2020-02-19 13:21 ` Johan Hovold
2020-02-19 16:37 ` Uwe Kleine-König
2020-02-19 17:17 ` Johan Hovold
2020-02-20 11:04 ` Uwe Kleine-König
2020-02-25 8:55 ` Johan Hovold
2020-02-25 9:05 ` Uwe Kleine-König
2020-02-13 9:15 ` [PATCH v6 3/4] tty: new helper function tty_get_icount() Uwe Kleine-König
2020-02-13 9:16 ` [PATCH v6 4/4] leds: trigger: implement a tty trigger Uwe Kleine-König
2020-02-19 10:52 ` Johan Hovold
2020-02-19 11:03 ` Uwe Kleine-König
2020-02-19 11:19 ` Johan Hovold [this message]
2020-02-19 12:48 ` Johan Hovold
2020-02-19 10:40 ` [PATCH v6 0/4] " Greg Kroah-Hartman
2020-02-26 14:02 ` Pavel Machek
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