linux-kernel - Re: [PATCH] Input: Do not add SYN_REPORT in between a single packet data

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Date:	Thu, 7 Apr 2016 02:13:37 +0530
From:	Aniroop Mathur <aniroop.mathur@...il.com>
To:	Henrik Rydberg <rydberg@...math.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Aniroop Mathur <a.mathur@...sung.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Input: Do not add SYN_REPORT in between a single packet data

Hello Mr. Henrik,

On Thu, Apr 7, 2016 at 1:21 AM, Henrik Rydberg <rydberg@...math.org> wrote:
> Hi Aniroop,
>
>>> I am not sure what the urgency is. It is more of a theoretical problem
>>> ans so far the proposed solutions were actually introducing more
>>> problems than they were solving.
>>>
>>> I am sorry, bit this particular topic is not a priority for me.
>>>
>>
>> There is no hurry at all. :-) As you know request is made a long time ago,
>> so I am only very curious to complete it.
>
> This kind of patch is not liked by any maintainer, because it does not solve any
> immediate problem, but instead may create one. If such a simple patch takes
> three of four tries to look right, it only adds to the perception that the code
> is best left alone.
>
> I think the solution at this stage is to say no to this patch.
>
> If there is ever a driver for which the input_estimate_events_per_packet()
> function returns less than the actual maximum number of events per frame, this
> issue can be revisited and resolved in a number of different ways.
>
> Sorry, and thanks for your work.
>

Well, I agree this code might not be used by any driver so far.
But if some driver developer writes such a driver, then it definitely cannot
work well because of the bug in input subsystem code. So I am afraid that it
is not a good idea to wait for someone to report this bug when we already know
that the bug does exist in input core.

Secondly, I submitted this patch not only because it breaks protocol of
SYN_REPORT event but also because without this bug fix, another bug could not
be concluded which depends on when the input event packet ended really.
Bug:
Input: evdev: fix bug of dropping valid packet after syn_dropped event
https://patchwork.kernel.org/patch/8083641/
So to fix this bug, we need to fix SYN_REPORT bug first.

It would be appreciating of you if you could give it one more spin.

> Henrik
>