linux-kernel - Re: [PATCH v4 01/24] input: Add ff-memless-next module

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Date:	Wed, 21 May 2014 18:42:40 -0400
From:	simon@...gewell.org
To:	"Roland Bosa" <rbosa@...itech.com>
Cc:	"Elias Vanderstuyft" <elias.vds@...il.com>,
	"Michal MalÃ½" 
	<madcatxster@...oid-pointer.net>,
	"Dmitry Torokhov" <dmitry.torokhov@...il.com>,
	"HID CORE LAYER" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Jiri Kosina" <jkosina@...e.cz>,
	"Anssi Hannula" <anssi.hannula@....fi>,
	"Simon Wood" <simon@...gewell.org>
Subject: Re: [PATCH v4 01/24] input: Add ff-memless-next module


>> But 2 Spring effects with different offsets and non-zero effective
>> force can't be combined into a single slot (without streaming them
>> with Constant force), right?
>
> Yes - you cannot *download* two springs to a single slot. You need to
> choose (allocate) one of them. The winner gets the slot. The losers go
> somewhere else (they might get discarded, they might get simulated).

In reverse engineering, I thought that a single slot could hold two
rotational angles/points (at which a springs would start) and that that
the direction could be set so that both acting in the same direction with
different forces.
--
    Byte 2 - 0x_1
    Byte 3 - Clockwise angle, nominally on left (0x00..0xFF - 0x00 is
fully left)
    Byte 4 - Anti-Clockwise angle, nominally on right(0x00..0xFF)
    Byte 5 - L/R Proportion force, upper nibble clockwise + lower nibble
anti-clockwise (each 0x0..0xF)
    Byte 6 - Reverse Direction; upper nibble clockwise + lower nibble
anti-clockwise (each 0x0..0x1)
    Byte 7 - Force (0x00..0xFF)
--

Ie. turning from fully left (00) with no force, you could hit a 'weak'
spring (at 40) and then a 'stronger' spring (at 80).

So to some degree you /can/ merge springs... but I'm not saying that you
should :-).
Simon

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