Re: [PATCH-V2 1/1] HID: Force feedback support for the Logitech G920
From: Elias Vanderstuyft
Date: Fri Jan 15 2016 - 17:35:39 EST
On Mon, Jan 11, 2016 at 12:25 AM, Edwin Velds <e.velds@xxxxxxxxx> wrote:
> This patch implements force feedback support for the Logitech
> G920 Driving Force Racing Wheel. It is a generic implementation
> of feature 0x8123 of the Logitech HID++ protocol and should be
> usable for any future devices that implement this feature.
> This patch should be applied after the basic G920 support patch
> by Simon Wood:
> The driving supports everything that is supported by the G920
> and for version 2 firmware also:
> Both envelopes and replay values are supported as well, but some
> problems may occur when using firmware release 1. There is also a
> small residual clockwise damper in the wheel when using the first
> firmware release. All problems are fixed in the soon te be released
> firmware version 2.
> The default spring is disabled by permanently placing a spring
> force in the wheel. This spring is also used as the autocenter
> Signed-off-by: Edwin Velds <e.velds@xxxxxxxxx>
Tested-by: Elias Vanderstuyft <elias.vds@xxxxxxxxx>
Tested with both firmware version 1 and firmware version 2.
As side note, Edwin intentionally did *not* put a clamp(0, 0x7FFF, x)
in the driver,
with x being envelope.attack_level or envelope.fade_level,
since this parameter checking is (/ should be) the task of "ff_core.c".
The device will behave odd when playing an effect that violates this rule,
although most user-space programs don't let them exceed 0x7FFF.
So this is a TODO for "ff-core.c", but not a blocker for this patch,
since the odd behavior will only be triggered during playback of such
and vanishes when the effect stops.
For anyone who is interested on which spec this patch is based,
take a look at the excellently written "Logitech Force Feedback