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([2001:a61:1366:6801:b2db:904d:e0b0:46ec]) by smtp.gmail.com with ESMTPSA id k9-20020a05600c1c8900b00410d7e55e5asm2630204wms.3.2024.02.12.04.22.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Feb 2024 04:22:44 -0800 (PST) Message-ID: Date: Mon, 12 Feb 2024 13:22:42 +0100 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] media: ucvideo: Add quirk for Logitech Rally Bar To: Laurent Pinchart , Ricardo Ribalda Cc: Greg Kroah-Hartman , Alan Stern , Mauro Carvalho Chehab , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, stable@vger.kernel.org References: <20240108-rallybar-v4-1-a7450641e41b@chromium.org> <20240204105227.GB25334@pendragon.ideasonboard.com> Content-Language: en-US From: Oliver Neukum In-Reply-To: <20240204105227.GB25334@pendragon.ideasonboard.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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. 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. I am sorry, but it seems to me that the exceptions need to go into usbcore. Regards Oliver