From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2895D1775C; Tue, 13 Feb 2024 10:47:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707821245; cv=none; b=ZssUiCFkslxCBRdCeqac/qGtNBF3AJi9I3DshU+cUQr1mJSE/Ve6n5AjXbpTj/EgiGDHQpsve2FExC7qRcT0aTktFqTL8yEGwWFWP+V2HatjVUa/jN3OUBnB4qoY0CikR/m4qWxKOPxT9nDOWZ6hWA97Ib/mL7VQ9eQyyPk7SVM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707821245; c=relaxed/simple; bh=LuZVB9/U46GxT3gi1nHL2CZ0+ZTFaMf0rDsOE7bl3hk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uYOwy8fdnzpRniTJOkdVxnE5L5lU6RhNqGtst0Yk0bWEXJMpkSECmDrNrwSoMUdcT0WTcQBhnFvfUTkTUXKkJFEG/mgxP3myTLY3gcnm5zkugkVYFL4kMsb3We+RIZJ5SjmpmaV5Jg4kzeUypfPNJar4N090MfGVQEMVbe1qCog= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=TmEu4/T4; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="TmEu4/T4" Received: from pendragon.ideasonboard.com (unknown [109.130.69.237]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 1569C675; Tue, 13 Feb 2024 11:47:20 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1707821240; bh=LuZVB9/U46GxT3gi1nHL2CZ0+ZTFaMf0rDsOE7bl3hk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TmEu4/T4muelKKgbtFKqcPolTwHWbmCtPpMzX1aE0RScaQOkVU/BGQgyw6wrWKzCD ruxiLIkknUu5+KyeEq5ajNihe/TYwdmADq3l6qko5002lmZCjS4dv4J2QvBQXbf9+2 cX5Q1mqXJZFRmShzYgg4q5TfIhlfbBNL2BMKFsRs= Date: Tue, 13 Feb 2024 12:47:25 +0200 From: Laurent Pinchart To: Alan Stern Cc: Oliver Neukum , Ricardo Ribalda , Greg Kroah-Hartman , Mauro Carvalho Chehab , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v4] media: ucvideo: Add quirk for Logitech Rally Bar Message-ID: <20240213104725.GC5012@pendragon.ideasonboard.com> References: <20240108-rallybar-v4-1-a7450641e41b@chromium.org> <20240204105227.GB25334@pendragon.ideasonboard.com> <6aade777-d97c-4c65-b542-14ce5b39abb6@rowland.harvard.edu> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <6aade777-d97c-4c65-b542-14ce5b39abb6@rowland.harvard.edu> On Mon, Feb 12, 2024 at 02:04:31PM -0500, Alan Stern wrote: > On Mon, Feb 12, 2024 at 01:22:42PM +0100, Oliver Neukum wrote: > > On 04.02.24 11:52, Laurent Pinchart wrote: > > > Hi Ricardo, > > > > > > Thank you for the patch. > > > > Hi, > > > > sorry for commenting on this late, but this patch has > > a fundamental issue. In fact this issue is the reason the > > handling for quirks is in usbcore at all. > > > > If you leave the setting/clearing of this flag to a driver you > > are introducing a race condition. The driver may or may not be > > present at the time a device is enumerated. And you have > > no idea how long the autosuspend delay is on a system > > and what its default policy is regarding suspending > > devices. > > That means that a device can have been suspended and > > resumed before it is probed. On a device that needs > > RESET_RESUME, we are in trouble. > > Not necessarily. If the driver knows that one of these devices may > already have been suspend and resumed, it can issue its own preemptive > reset at probe time. > > > The inverse issue will arise if a device does not react > > well to RESET_RESUME. You cannot rule out that a device > > that must not be reset will be reset. > > That's a separate issue, with its own list of potential problems. > > > I am sorry, but it seems to me that the exceptions need > > to go into usbcore. > > If we do then we may want to come up with a better scheme for seeing > which devices need to have a quirk flag set. A static listing probably > won't be good enough; the decision may have to be made dynamically. I don't mind either way personally. Oliver, could you try to find a good solution with Ricardo ? I'll merge the outcome. -- Regards, Laurent Pinchart