From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755183AbbLKXgi (ORCPT ); Fri, 11 Dec 2015 18:36:38 -0500 Received: from lists.s-osg.org ([54.187.51.154]:38124 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752748AbbLKXgg (ORCPT ); Fri, 11 Dec 2015 18:36:36 -0500 Subject: Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered To: Javier Martinez Canillas , linux-kernel@vger.kernel.org References: <1449874629-8973-1-git-send-email-javier@osg.samsung.com> <1449874629-8973-2-git-send-email-javier@osg.samsung.com> Cc: Mauro Carvalho Chehab , Sakari Ailus , Laurent Pinchart , Hans Verkuil , linux-media@vger.kernel.org, Shuah Khan From: Shuah Khan X-Enigmail-Draft-Status: N1110 Organization: Samsung Open Source Group Message-ID: <566B5DFB.3020100@osg.samsung.com> Date: Fri, 11 Dec 2015 16:36:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <1449874629-8973-2-git-send-email-javier@osg.samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/11/2015 03:57 PM, Javier Martinez Canillas wrote: > Most media functions that unregister, check if the corresponding register > function succeed before. So these functions can safely be called even if a > registration was never made or the component as already been unregistered. > > Add the same check to media_device_unregister() function for consistency. > > This will also allow to split the media_device_register() function in an > initialization and registration functions without the need to change the > generic cleanup functions and error code paths for all the media drivers. > > Suggested-by: Sakari Ailus > Signed-off-by: Javier Martinez Canillas > Acked-by: Sakari Ailus > > --- > > Changes in v5: None > Changes in v4: None > Changes in v3: None > Changes in v2: > - Reword the documentation for media_device_unregister(). Suggested by Sakari. > - Added Sakari's Acked-by tag for patch #1. > > drivers/media/media-device.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > index c12481c753a0..11c1c7383361 100644 > --- a/drivers/media/media-device.c > +++ b/drivers/media/media-device.c > @@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register); > * media_device_unregister - unregister a media device > * @mdev: The media device > * > + * It is safe to call this function on an unregistered > + * (but initialised) media device. > */ > void media_device_unregister(struct media_device *mdev) > { > @@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev) > struct media_entity *next; > struct media_interface *intf, *tmp_intf; > > + /* Check if mdev was ever registered at all */ > + if (!media_devnode_is_registered(&mdev->devnode)) > + return; This is a good check, however, this check will not prevent media_device_unregister() from getting run twice by two different drivers. i.e media_devnode gets unregistered towards the end of at the end of media_device_unregister(). In an example case, if bridge driver and snd-usb-aduio both call media_device_unregister(), this check won't help prevent media_device_unregister() being done only once. I think we need a different state variable in struct media_device to ensure unregister is done only once. > + > /* Remove all entities from the media device */ > list_for_each_entry_safe(entity, next, &mdev->entities, graph_obj.list) > media_device_unregister_entity(entity); > -- Shuah Khan Sr. Linux Kernel Developer Open Source Innovation Group Samsung Research America (Silicon Valley) shuahkh@osg.samsung.com | (970) 217-8978