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[85.228.170.18]) by smtp.gmail.com with ESMTPSA id 11sm1032702lju.103.2020.02.19.03.19.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Feb 2020 03:19:16 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.92.3) (envelope-from ) id 1j4NNp-0000wX-R8; Wed, 19 Feb 2020 12:19:13 +0100 Date: Wed, 19 Feb 2020 12:19:13 +0100 From: Johan Hovold To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Johan Hovold , Jacek Anaszewski , Pavel Machek , Dan Murphy , Greg Kroah-Hartman , Jiri Slaby , 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 Message-ID: <20200219111913.GB32540@localhost> References: <20200213091600.554-1-uwe@kleine-koenig.org> <20200213091600.554-5-uwe@kleine-koenig.org> <20200219105239.GA32540@localhost> <20200219110306.k5jndutalll64esu@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200219110306.k5jndutalll64esu@pengutronix.de> Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org 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 > > > > > > 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 > > > --- > > > > > +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