From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Slaby Subject: Re: FF layer restrictions [Was: [PATCH 1/1] Input: add sensable phantom driver] Date: Wed, 21 Mar 2007 14:31:08 +0100 Message-ID: <4601339C.6010706@gmail.com> References: <2460126662758025813@fi.muni.cz> <4af2d03a0703130919nb4893b1ja9ec795dcf4bf53c@mail.gmail.com> <38b3b7c0703131450v2646e63fj2be4b9dda7f928c0@mail.gmail.com> <45F722CE.9000602@gmail.com> <45F82626.8000108@gmail.com> <45F83930.4060401@gmail.com> <8e4ff20a0703141147n4b690ab8g4cc8138d1ecc94e1@mail.gmail.com> <8e4ff20a0703141218r3add7923n74470b5e16f58c5c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <8e4ff20a0703141218r3add7923n74470b5e16f58c5c@mail.gmail.com> Sender: owner-linux-input@atrey.karlin.mff.cuni.cz List-Help: List-Owner: List-Post: List-Unsubscribe: To: =?UTF-8?B?IlNUZW55YUsgKEJydW5vIEdvbnrDoWxleiki?= Cc: Dmitry Torokhov , Anssi Hannula , johann deneux , Linux kernel mailing list , linux-input@atrey.karlin.mff.cuni.cz List-Id: linux-input@vger.kernel.org STenyaK (Bruno Gonz=C3=A1lez) napsal(a): > On 3/14/07, Dmitry Torokhov wrote: >> > I have a question: if the force is to be 3D, why only 3 possible >> values? >> > What would they be, 3 torques or 3 forces? In the case of car sims (= ff >> > steering wheels), only one axis of torque is usually used (except >> for 6 dof >> > platforms, as mentioned). >> > >> >> I wonder if we could somehow extend or augment FF envelope se we could >> specify a plane for the effect.. Then a vector could be represented by >> a sum 3 constant effects in 3 separate planes and we could also use >> spring and other effects as well. >=20 > Ideally, afaik we should use: > -3 values for translation force (linear force): x,y,z components of > the force vector. > -4 values for rotation force (torque): x,y,z,w components of the > quaternion. You can also use euler angles (and i think there are > another one or two notations), which is just 3 values, but i'm not > sure it will be a correct decision (due to the gimbal lock problem, > which may or may not be present in ff devices, dunno). So, the resolution is? Since I want no longer have out-of-kernel driver, = I need to know how to implement the phantom driver -- merge it `as is', i.e= . control through mmio or rewrite ff layer somehow, and in that case how? There seem to be only few possibilities: - new 3D effect, which will be problematic in any other future use, that = may need more than 3 axis. no matter if torques or vector is passed -- depend= ing on device and programmer (as I need to compute torques from forces in FP)= . Maybe struct with 2x 3 axis is OK - "raw" effect, which may contain more axis, but this is ugly in Anssi's = eyes - something else? (did I forget something) thanks, --=20 http://www.fi.muni.cz/~xslaby/ Jiri Slaby faculty of informatics, masaryk university, brno, cz e-mail: jirislaby gmail com, gpg pubkey fingerprint: B674 9967 0407 CE62 ACC8 22A0 32CC 55C3 39D4 7A7E