Re: input.h changes

[Vojtech P. <vo...@su...>]

On Thu, Jan 31, 2002 at 12:06:40AM +0100, Johann Deneux wrote:
> Hi,
> 
> I am changing the ff_effect struct. I went for the 1-parameter-1-effect
> scheme (actually it's really (1,2)-parameter(s)-1-effect).
> 
> New effect types:
> * FF_DAMPER
> This effect really is the former FF_FRICTION.
> * FF_INERTIA
> * FF_RAMP
> Note that this effect is not periodic. Reasons:
>  1. PID does not define it as a periodic effect
>  2. A periodic ramp is just a sawtooth up or down
> I wonder if we still need the FF_CONSTANT, as it's just a special case of
> FF_RAMP.

There might be a device which doesn't support RAMP, but does support CONSTANT.

> * FF_CUSTOM
> It's not new actually. I just did not remember it was there.
> 
> New or changed structures:
> * Ramp effects
> struct ff_ramp_effect {
>         _s16 start_level;
>         _s16 end_level;
>         struct ff_shape shape;
> }
> * Friction
> No new structure. We can use the ff_interactive, according to PID. What is
> its meaning is still not clear. I would guess the following:
> force = f(position, direction)
> force.direction = -direction
> force.magnitude = p(position), p being the function described at page 12.
> The ff_interactive_effect structure has changed:
> struct ff_interactive_effect {
>         __u16 right_saturation[2]; /* Max level when joystick is on the
> right */
>         __u16 left_saturation[2];  /* Max level when joystick in on the
> left */
> 
>         __s16 right_coeff[2];   /* Indicates how fast the force grows when
> the
>                                    joystick moves to the right */
>         __s16 left_coeff[2];    /* Same for left side */
> 
>         __u16 deadband[2];      /* Size of area where no force is produced
> */
>         __s16 center[2];        /* Position of dead zone */
> 
> };
> 
> Note the arrays. There is one value for each axis. The axis mumber has
> become useless and has therefore been droped.
> 
> * ff_periodic_effect:
> struct ff_periodic_effect {
>         __u16 waveform;         /* Kind of wave (sine, square...) */
>         __u16 period;           /* in ms */
>         __s16 magnitude;        /* Peak value */
>         __s16 offset;           /* Mean value of wave (roughly) */
>         __u16 phase;            /* 'Horizontal' shift */
> 
>         struct ff_shape shape;
> 
> /* Only used if waveform == FF_CUSTOM */
>         __u32 custom_len;       /* Number of samples  */
>         __s16 *custom_data;     /* Buffer of samples */
> /* Note: the data pointed by custom_data is copied by the driver. You can
>  * therefore dispose of the memory after the upload/update */
> };
> 
> The _u32 for the number of samples is a bit oversized, maybe.
> 
> 
> I think that's all for now. Comments and critics welcome.

Looks OK. Maybe we should get rid of FF_ABS then? Maybe FF_BTN as well?

-- 
Vojtech Pavlik
SuSE Labs