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[209.85.222.178]) by smtp.gmail.com with ESMTPSA id oh8-20020a056214438800b0068f5a422773sm2181104qvb.14.2024.02.19.07.13.49 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Feb 2024 07:13:49 -0800 (PST) Received: by mail-qk1-f178.google.com with SMTP id af79cd13be357-7872bc61fcdso201719885a.2 for ; Mon, 19 Feb 2024 07:13:49 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCVlxxndtAHuWrPhQ5uu1ijECWaMdWaSw+YqNjbM2oux6YP+3JfJ42XR+Y8Zq7z9IAT/P4JE5vRLgE3h/HXhzbUERXfIHNiDLx4F35s= X-Received: by 2002:a0c:e0d2:0:b0:68f:2ac1:99fe with SMTP id x18-20020a0ce0d2000000b0068f2ac199femr11694403qvk.45.1708355628695; Mon, 19 Feb 2024 07:13:48 -0800 (PST) Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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> In-Reply-To: <20240213104725.GC5012@pendragon.ideasonboard.com> From: Ricardo Ribalda Date: Mon, 19 Feb 2024 16:13:31 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4] media: ucvideo: Add quirk for Logitech Rally Bar To: Laurent Pinchart Cc: Alan Stern , 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 Content-Type: text/plain; charset="UTF-8" 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 -- Ricardo Ribalda