Re: FF layer restrictions [Was: [PATCH 1/1] Input: add sensable phantom driver]

[johann deneux]

On 3/27/07, Jiri Slaby <jirislaby@xxxxxxxxx> wrote:

> Ok, so how to deal with these devices? Does anybody have some idea? That's
> what I was talking about somewhere in the beginning of this thread, the raw
> values, because it seems too specific for letting kernel to cope with each
> of these devices separately, but there might be a better idea in somebody's
> head? But raw is ugly...

What about adding a member to ff_effect which would be the number of the motor?
We can't change the layout of ff_effect too much though, so we have to
find unused bits and put them to work.

For instance, we could replace

__u16 type;

by

__u8 motor;
__u8 type;

since 16 bits seems way more than needed for the effect type.

Another possibility is to get rid of "trigger" and replace it by __u8
motor and some padding, since that's I-Force specific (are there other
drivers that implement that?). The goal of "trigger" is to start an
effect when a button is pressed, which can be done from userland
instead. It's not like we need micro-second latency when starting
effects.

As a reminder, here is the current definition of ff_effect:

struct ff_effect {
      __u16 type;
      __s16 id;
      __u16 direction;
      struct ff_trigger trigger;
      struct ff_replay replay;

      union {
              struct ff_constant_effect constant;
              struct ff_ramp_effect ramp;
              struct ff_periodic_effect periodic;
              struct ff_condition_effect condition[2]; /* One for each axis */
              struct ff_rumble_effect rumble;
      } u;
};

--
Johann
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