linux-kernel - Re: [PATCH] Input: MT - Add support for balanced slot assignment

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Message-ID: <54C15C61.9000100@bitmath.org>
Date:	Thu, 22 Jan 2015 21:24:01 +0100
From:	Henrik Rydberg <rydberg@...math.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: MT - Add support for balanced slot assignment

Hi Dmitry,

On 01/22/2015 09:02 PM, Dmitry Torokhov wrote:
> On Thu, Jan 22, 2015 at 08:52:25PM +0100, Henrik Rydberg wrote:
>>  int input_mt_assign_slots(struct input_dev *dev, int *slots,
>> -			  const struct input_mt_pos *pos, int num_pos)
>> +			  const struct input_mt_pos *pos, int num_pos,
>> +			  int dmax)
> 
> Should dmax be unsigned and do we really need to treat 0 specially or we
> could use UNIT_MAX as "don't care" value?

We could have dmax unsigned, but it does not have to be from a branching
perspective, since the square is what gets used anyways.

>>  {
>>  	struct input_mt *mt = dev->mt;
>> +	int mu = 2 * dmax * dmax;
> 
> For my education, what does "mu" stand for?

I chose mu because of the mathematical similarity to the chemical potential in
statistical mechanics, where it denotes the energy per particle. Here, it
denotes the energy per contact assignment.

> Ideally, if someone could create a
> write-up on the contact matching that would be most awesome.

Heh, I guess I will have to write something at some point, without requiring
prior knowledge of Lagrange relaxation or the like. Time is a luxury these days...

Henrik

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