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Tue, 23 Jun 2026 06:17:41 -0700 (PDT) Date: Tue, 23 Jun 2026 09:17:38 -0400 From: Alan Stern To: Nikhil Solanke Cc: linux-usb@vger.kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, michal.pecio@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH] usbcore: Add quirk for 255-bytes initial config read Message-ID: <933c5d7a-e512-460a-992c-25be64ff48cf@rowland.harvard.edu> References: <20260619095936.24080-1-nikhilsolanke5@gmail.com> <8175e40d-357a-4513-b827-752f679e9904@rowland.harvard.edu> <8da4a00f-a01c-4b38-82a3-a718e5588f51@rowland.harvard.edu> 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-Disposition: inline In-Reply-To: On Tue, Jun 23, 2026 at 01:01:12PM +0530, Nikhil Solanke wrote: > I have a v2 patch ready with all the requested changes along with the > documentation in Documentation/admin-guide/kernel-parameters.txt. Is > there any other place where I have to write documentation? No. > Also, I would like to know the "low-level" type reason as to why do we > have 2 separate buffers. a desc and then a bigbuffer? Why don't we > just realloc the desc buffer? Does this have something to do with > reallocs in general? No particular reason. I guess it just seemed more straightforward to allocate a second, larger buffer than to expand the first, smaller buffer. > Also (a bit more tangent), can the usb device potentially fingerprint > the host os? if we are asking for 9 bytes first and windows ask for > 255, is it possible that some usb devices will fingerprint the OS > based on this, and behave differently? are there any other such places > where fingerprinting is possible? In those cases, is it theoretically > possible that this patch might fix some weird devices that "seem to > work" on windows but not on linux? Of course it's possible. Devices can do whatever they want, as long as they obey the requirements of the USB spec. > I might just add this one line to > documentation that it might theoretically fix other usb devices as > well instead of it just being a quirk to fix a game controller. Isn't that true of any quirk? As a theoretical possibility, I mean. Alan Stern