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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 0FD3BC4332B for ; Tue, 24 Mar 2020 10:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6637208C3 for ; Tue, 24 Mar 2020 10:20:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726845AbgCXKU1 (ORCPT ); Tue, 24 Mar 2020 06:20:27 -0400 Received: from relay12.mail.gandi.net ([217.70.178.232]:35115 "EHLO relay12.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727150AbgCXKU1 (ORCPT ); Tue, 24 Mar 2020 06:20:27 -0400 Received: from classic (mon69-7-83-155-44-161.fbx.proxad.net [83.155.44.161]) (Authenticated sender: hadess@hadess.net) by relay12.mail.gandi.net (Postfix) with ESMTPSA id A326D200011; Tue, 24 Mar 2020 10:20:22 +0000 (UTC) Message-ID: <92f48f409e913299c12322d195c88792bb4e5c9c.camel@hadess.net> Subject: Re: [PATCH v2] HID: logitech-dj: issue udev change event on device connection From: Bastien Nocera To: Filipe =?ISO-8859-1?Q?La=EDns?= , Jiri Kosina , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Hutterer , Hans de Goede , Mario Limonciello , Richard Hughes Date: Tue, 24 Mar 2020 11:20:21 +0100 In-Reply-To: <20200318192721.390630-1-lains@archlinux.org> References: <20200318161906.3340959-1-lains@archlinux.org> <20200318192721.390630-1-lains@archlinux.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.0 (3.36.0-1.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On Wed, 2020-03-18 at 19:27 +0000, Filipe Laíns wrote: > As discussed in the mailing list: > > > Right now the hid-logitech-dj driver will export one node for each > > connected device, even when the device is not connected. That > > causes > > some trouble because in userspace we don't have have any way to > > know if > > the device is connected or not, so when we try to communicate, if > > the > > device is disconnected it will fail. Why is it a problem that user-space communication fails? Note that sending a signal without any way to fetch the state means that it's always going to be racy. > The solution reached to solve this issue is to trigger an udev change > event when the device connects, this way userspace can just wait on > those connections instead of trying to ping the device. > > Signed-off-by: Filipe Laíns > > --- > > v2: > - Issue udev change event on the connected hid device, not on the > receiver > > --- > drivers/hid/hid-logitech-dj.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid- > logitech-dj.c > index 48dff5d6b605..282e57dd467d 100644 > --- a/drivers/hid/hid-logitech-dj.c > +++ b/drivers/hid/hid-logitech-dj.c > @@ -1412,6 +1412,7 @@ static int logi_dj_dj_event(struct hid_device > *hdev, > { > struct dj_receiver_dev *djrcv_dev = hid_get_drvdata(hdev); > struct dj_report *dj_report = (struct dj_report *) data; > + struct dj_device *dj_dev; > unsigned long flags; > > /* > @@ -1447,7 +1448,9 @@ static int logi_dj_dj_event(struct hid_device > *hdev, > > spin_lock_irqsave(&djrcv_dev->lock, flags); > > - if (!djrcv_dev->paired_dj_devices[dj_report->device_index]) { > + dj_dev = djrcv_dev->paired_dj_devices[dj_report->device_index]; > + > + if (!dj_dev) { > /* received an event for an unknown device, bail out */ > logi_dj_recv_queue_notification(djrcv_dev, dj_report); > goto out; > @@ -1464,6 +1467,8 @@ static int logi_dj_dj_event(struct hid_device > *hdev, > if (dj_report- > >report_params[CONNECTION_STATUS_PARAM_STATUS] == > STATUS_LINKLOSS) { > logi_dj_recv_forward_null_report(djrcv_dev, > dj_report); > + } else { > + kobject_uevent(&dj_dev->hdev->dev.kobj, > KOBJ_CHANGE); > } > break; > default: