Re: [PATCH 4/8] HID: input: use the Resolution Multiplier for high-resolution scrolling

[Linus Torvalds]

On Thu, Nov 22, 2018 at 3:28 PM Peter Hutterer <peter.hutterer@xxxxxxxxx> wrote:
>
> The device sends hi-res values of 4, so it should end up as REL_WHEEL_HI_RES
> 30. We are getting 28 instead which doesn't add up to a nice 120.

I think you're just doing the math in the wrong order.

Why don't you just do

    update = val * 120 / multiplier

which gives you the expected "30".

It seems you have done the "120 / multiplier" too early, and you force
that value into "wheel_factor". Don't. Do all the calculations
(including all the accumulated ones) in the original values, and only
do the "multiply by 120 and divide by multiplier" at the very end.

Hmm?

              Linus