From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F1F5C43467 for ; Tue, 20 Oct 2020 12:36:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B88CA22265 for ; Tue, 20 Oct 2020 12:36:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406258AbgJTMgN (ORCPT ); Tue, 20 Oct 2020 08:36:13 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:47486 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406246AbgJTMgM (ORCPT ); Tue, 20 Oct 2020 08:36:12 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 04A411C0B8D; Tue, 20 Oct 2020 14:36:10 +0200 (CEST) Date: Tue, 20 Oct 2020 14:36:09 +0200 From: Pavel Machek To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Jacek Anaszewski , Dan Murphy , Greg Kroah-Hartman , Jiri Slaby , kernel@pengutronix.de, linux-kernel@vger.kernel.org, Johan Hovold , linux-leds@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH v9 3/3] leds: trigger: implement a tty trigger Message-ID: <20201020123609.GD19856@duo.ucw.cz> References: <20201018204022.910815-1-u.kleine-koenig@pengutronix.de> <20201018204022.910815-4-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Xm/fll+QQv+hsKip" Content-Disposition: inline In-Reply-To: <20201018204022.910815-4-u.kleine-koenig@pengutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Xm/fll+QQv+hsKip Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > Usage is as follows: >=20 > myled=3Dledname > tty=3DttyS0 >=20 > echo tty > /sys/class/leds/$myled/trigger > echo $tty > /sys/class/leds/$myled/ttyname >=20 > . 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. >=20 > Signed-off-by: Uwe Kleine-K=F6nig > --- > +static ssize_t ttyname_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct ledtrig_tty_data *trigger_data =3D led_trigger_get_drvdata(dev); > + ssize_t len =3D 0; Unused value. Not sure if some checker will complain. > +static ssize_t ttyname_store(struct device *dev, > + struct device_attribute *attr, const char *buf, > + size_t size) > +{ > + struct ledtrig_tty_data *trigger_data =3D led_trigger_get_drvdata(dev); > + char *ttyname; > + ssize_t ret =3D size; > + ledtrig_tty_halt(trigger_data); > + > + mutex_lock(&trigger_data->mutex); > + > + if (size > 0 && buf[size - 1] =3D=3D '\n') > + size -=3D 1; > + > + if (size) { > + ttyname =3D kmemdup_nul(buf, size, GFP_KERNEL); > + if (!ttyname) { > + ret =3D -ENOMEM; > + goto out_unlock; If this happens, you return error to the user and trigger_data->ttyname remains with the old value, but trigger is now stopped. That is not exactly consistent. > +static void ledtrig_tty_work(struct work_struct *work) > +{ > + struct ledtrig_tty_data *trigger_data =3D > + container_of(work, struct ledtrig_tty_data, dwork.work); > + struct serial_icounter_struct icount; > + int ret; > + > + mutex_lock(&trigger_data->mutex); > + > + BUG_ON(!trigger_data->ttyname); > + > + /* try to get the tty corresponding to $ttyname */ > + if (!trigger_data->tty) { > + dev_t devno; > + struct tty_struct *tty; > + int ret; > + > + ret =3D tty_dev_name_to_number(trigger_data->ttyname, &devno); > + if (ret < 0) > + /* > + * A device with this name might appear later, so keep > + * retrying. > + */ > + goto out; Poll every 100 msec... Hmm.... Okay, I guess? > + ret =3D tty_get_icount(trigger_data->tty, &icount); > + if (ret) { > + mutex_unlock(&trigger_data->mutex); > + dev_info(trigger_data->tty->dev, "Failed to get icount, stopped pollin= g\n"); > + mutex_unlock(&trigger_data->mutex); Eh? > + return; > + } > + > + if (icount.rx !=3D trigger_data->rx || > + icount.tx !=3D trigger_data->tx) { > + led_set_brightness(trigger_data->led_cdev, LED_ON); Are you sure about LED_ON here? It should use current brightness selected by brightness file... > +static int ledtrig_tty_activate(struct led_classdev *led_cdev) > +{ > + struct ledtrig_tty_data *trigger_data; > + > + trigger_data =3D kzalloc(sizeof(*trigger_data), GFP_KERNEL); > + if (!trigger_data) > + return -ENOMEM; > + > + led_set_trigger_data(led_cdev, trigger_data); > + > + INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work); > + trigger_data->led_cdev =3D led_cdev; > + mutex_init(&trigger_data->mutex); How is this protected from concurrent access from sysfs? Best regards, Pavel --=20 http://www.livejournal.com/~pavelmachek --Xm/fll+QQv+hsKip Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCX47ZuQAKCRAw5/Bqldv6 8jLcAJ4yb82/HCdd/XZfoeI9zFLNCZgJagCgiWsD9kePtsTio6g9/pFmCBGVfN4= =WDRg -----END PGP SIGNATURE----- --Xm/fll+QQv+hsKip--