From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by smtp.subspace.kernel.org (Postfix) with SMTP id 849AA3FB02 for ; Fri, 22 Mar 2024 14:40:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.131.102.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711118449; cv=none; b=b1/JT7G7UB1ZLNUWqTdeCzmV+qa7pfdvbmVtYJSz3KtPDg4WR+HBUVBBO1GssfvTLVQFfjVVZFeV03UoCRkmMjB5wMuRx1LTJssYeBj+ZUK1BSm7C8K2OsmraR4/ghGrbsvjdmCeHHYXaZ/oRtfA7954RiTkOhwsrVnFKSkvC88= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711118449; c=relaxed/simple; bh=VmvTwIK00BUsWSa6IRrE06C6cD4KWMsHDZSl8m19mcU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sVOY8Aib6vBxdAE4GgT8x6k6ZH+wlj4VgdArpFpQE0nINPUQcIK/wD0WpKOUbNefW7StXwJnkwkUqL7bB41Je9MkN0qk4it6zPpWKkcHFpbCVanroNvgslectPX7BoCJRmwMB4m5DWGzUnjhe7hLJYoyQPH191zOsVkCHI1LmBA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=rowland.harvard.edu; spf=pass smtp.mailfrom=netrider.rowland.org; arc=none smtp.client-ip=192.131.102.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=rowland.harvard.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netrider.rowland.org Received: (qmail 761098 invoked by uid 1000); 22 Mar 2024 10:40:46 -0400 Date: Fri, 22 Mar 2024 10:40:46 -0400 From: Alan Stern To: Laurent Pinchart Cc: Ricardo Ribalda , Oliver Neukum , 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: <588d2e1f-1cb5-4868-9160-11a36e8640d6@rowland.harvard.edu> References: <20240108-rallybar-v4-1-a7450641e41b@chromium.org> <20240204105227.GB25334@pendragon.ideasonboard.com> <6aade777-d97c-4c65-b542-14ce5b39abb6@rowland.harvard.edu> <20240213104725.GC5012@pendragon.ideasonboard.com> <20240322115734.GB31979@pendragon.ideasonboard.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20240322115734.GB31979@pendragon.ideasonboard.com> On Fri, Mar 22, 2024 at 01:57:34PM +0200, Laurent Pinchart wrote: > On Thu, Feb 29, 2024 at 05:57:38PM +0100, Ricardo Ribalda wrote: > > Oliver, friendly ping > > Seconded :-) We can help with the implementation, but we would like your > guidance on the direction you think this should take. Thirded :-) I want to hear what Oliver thinks about the original patch. Alan Stern > > On Mon, 19 Feb 2024 at 16:13, Ricardo Ribalda wrote: > > > > > > Hi Oliver > > > > > > Would you prefer a version like this? > > > > > > https://lore.kernel.org/all/20231222-rallybar-v2-1-5849d62a9514@chromium.org/ > > > > > > If so I can re-submit a version with the 3 vid/pids. Alan, would you > > > be happy with that? > > > > > > Regards! > > > > > > On Tue, 13 Feb 2024 at 11:47, Laurent Pinchart wrote: > > > > 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