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    SubjectRe: FF layer restrictions [Was: [PATCH 1/1] Input: add sensable phantom driver]
    On 3/27/07, Jiri Slaby <jirislaby@gmail.com> wrote:
    > Dmitry Torokhov napsal(a):
    > > On Wednesday 21 March 2007 18:03, johann deneux wrote:
    > >> On 3/21/07, Jiri Slaby <jirislaby@gmail.com> wrote:
    > >>> Dmitry Torokhov napsal(a):
    > >>>> On 3/21/07, johann deneux <johann.deneux@gmail.com> wrote:
    > >>>>> I would suggest adding a new effect type (3d effect) and extending the
    > >>>>> union in struct ff_effect.
    > >>>>> Let me know if I'm too vague, I already suggested that solution but
    > >>>>> got no answer. I wonder if my mail got lost, nobody understood what I
    > >>>>> said, or if it's just a plain bad idea.
    > >>>>>
    > >>>> My concern with a new 3D effect is that it will be a very "simple"
    > >>>> effect with only constant force apllied. That might be enough for
    > >>>> phantom but may not be sufficient for future devices. If we add
    > >>>> ability to specify a "plane" for an effect we will be able to add
    > >>>> envelopes on top of more complex effects and get desired combined
    > >>>> effcet.
    > >>> I didn't get this too much, because I don't understand the FF layer well so
    > >>> far. How is this going to work? Let's say, we have 3 torque values computed
    > >>> in US, and this structure:
    > >>>
    > >>> struct ff_effect {
    > >>> __u16 direction;
    > >>> struct ff_trigger trigger;
    > >>> struct ff_replay replay;
    > >>>
    > >>> struct ff_constant_effect {
    > >>> __s16 level;
    > >>> struct ff_envelope {
    > >>> __u16 attack_length;
    > >>> __u16 attack_level;
    > >>> __u16 fade_length;
    > >>> __u16 fade_level;
    > >>> };
    > >>> };
    > >>> };
    > >>>
    > >>> and need to pass the three 16bits torques into s16 ioaddr[0..2]. How?
    > >>>
    > >> Stupid question,
    >
    > Sorry to be out for so long, maybe I'm stupid idiot, that understands
    > nothing, but:

    No, it's not you, there are still things that are unclear. For
    instance I think Dmitry intended to combine several planes, which I
    don't understand.

    What we want is to specify a 3d vector, which can be done using two
    angles and a magnitude.
    One angle and the magnitude we already have in ff_effect, so all we
    need is an additional angle, which can be specified using a new ioctl.
    I originally thought it could be done without a new ioctl, just by
    extending ff_struct, but that won't work.

    >
    > >> I have forgotten the details of ioctl: Wouldn't the
    > >> following work?
    >
    > No, at least, as far as I understand this. I have computed _torques_, not
    > forces vector (this was misleading info in my first post), the question is
    > "how can I pass torques through plane and direction entries into KS?".

    Torques and forces are both represented as 3d vectors. Are we
    misunderstanding eachother maybe? By "vector" I mean a triplet of
    numbers, when you say "torques" and "forces vector", do you mean that
    each effect is composed of a bunch of torques?

    --
    Johann
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