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[83.28.36.56]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f85c6dc25sm50020765f8f.33.2026.07.27.12.18.19 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 27 Jul 2026 12:18:21 -0700 (PDT) Date: Mon, 27 Jul 2026 21:21:30 +0200 From: Michal Pecio To: Nikhil Solanke Cc: linux-usb@vger.kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu, corbet@lwn.net, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/2] usbcore: Add quirk for 255-bytes initial config read Message-ID: <20260727212130.4a6bb49f.michal.pecio@gmail.com> In-Reply-To: References: <20260717195336.98500-1-nikhilsolanke5@gmail.com> <20260717195336.98500-2-nikhilsolanke5@gmail.com> <20260726182946.79a4ef98.michal.pecio@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 27 Jul 2026 20:55:27 +0530, Nikhil Solanke wrote: > Regarding the "stall" wording, I was referring to the condition where > they fail with -EPIPE error when these devices are connected through > external usb hubs. The directly connected devices I've tested > typically fail with -EPROTO instead. I'm happy to reword the comment > if you think that would make it clearer. Understood. The reason you see -EPIPE is due to the marvel of technology which is "transaction translators" in USB 2.0 hubs. They report low/full-speed protocol errors with STALL handshake on the high-speed bus, even though a new ERR handshake is also defined and used for similar errors on interrupt endpoints only. So your device doesn't stall, it just disconnects as usual. And with a USB 1.0 hub you would see -EPROTO too, but these are rare today. My habit is to make code comments generic - I don't know what devices will use this quirk in the future, so just write something that likely applies to all of them - "break", "malfunction", "fail to respond". But I also describe precisely what problem the quirk was meant to solve in the commit, so the information can be found with "git blame". Regards, Michal