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Tue, 3 Sep 2024 20:37:01 -0400 (EDT) Date: Wed, 4 Sep 2024 10:36:49 +1000 From: Peter Hutterer To: "Gerecke, Jason" Cc: linux-input@vger.kernel.org, Benjamin Tissoires , Jiri Kosina , Dmitry Torokhov , Ping Cheng , "Tobita, Tatsunosuke" , Erin Skomra , Joshua Dickens , Jason Gerecke Subject: Re: [RFC PATCH] HID: wacom: Stop mangling tool IDs Message-ID: <20240904003649.GA1105191@quokka> References: <20240903182633.870892-1-jason.gerecke@wacom.com> Precedence: bulk X-Mailing-List: linux-input@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: <20240903182633.870892-1-jason.gerecke@wacom.com> On Tue, Sep 03, 2024 at 11:26:33AM -0700, Gerecke, Jason wrote: > From: Jason Gerecke > > In ancient times, an off-by-one-nybble error resulted in the Wacom > driver sending "mangled" tool IDs to userspace. This mangling behavior > was later enshrined into a function so that devices using the then-new > generic codepath could share the same broken behavior. The mangled IDs > have not historically been a major problem for userspace since few > applications care about the exact numeric value of the IDs. As long as > the IDs were unique it didn't much matter. Some programs (cross- > platform and remote-desktop applications in particular) /do/ rely on > the IDs being correct, however. > > This patch rids the driver of the mangling behavior. > > Signed-off-by: Jason Gerecke > References: 493630b20389 ("Input: wacom - fix serial number handling on Cintiq 21UX2") > References: 82527da319ee ("HID: wacom: Read and internally use corrected Intuos tool IDs") > --- > I'd like to get the opinion of the kernel maintainers on making a > change like this at some point in the future. There are _very_ few > userspace uses of these IDs (primarily: drivers, compositors, and > tablet control panels) and my plan is to update those bits and then > give some time for the changes to roll out to users before re- > submitting this for real. I don't expect any kind of breakage since > we'll be taking our time with the rollout and userspace needs to > have handling for "unknown" IDs anyway (since Wacom periodically > releases new pens). Just to show my support :) Acked-by: Peter Hutterer Cheers, Peter