linux-kernel - Re: [PATCH 02/12] Input: synaptics

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Message-ID: <CAGS+omBzzKWn+RgQ9m09F=F4HLqwH7=U6O4mO9dRw52V5k45hw@mail.gmail.com>
Date:	Wed, 6 Jul 2011 07:02:43 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	dmitry.torokhov@...il.com, chase.douglas@...onical.com,
	rubini@...l.unipv.it, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, derek.foreman@...labora.co.uk,
	daniel.stone@...labora.co.uk, olofj@...omium.org
Subject: Re: [PATCH 02/12] Input: synaptics - do not invert y if 0

On Wed, Jul 6, 2011 at 2:07 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
>> > > In some cases, however, y = 0 is sent by the touchpad.
>> > > In these cases, the kernel driver should not invert, and just report 0.
>> > >
>> > > This patch also refactors the inversion into a macro, and moves it
>> > > into packet processing instead of during position reporting.
>> >
>> > The patch seems to invert the current output?
>>
>> By 'current' do you mean referenced from the previous implementation?
>> Or referenced from the raw input.
>> It does indeed invert the raw input.
>> This is the same as the previous implementation did.
>> The difference is that it does not also invert the special 'y=0' into
>> an arbitrarily large value.
>> Is this your concern?
>
> It would be clearer to just change the argument of the
> input_report_abs() instances, would it not? An explanation why zero,
> outside the value range, should be output also needs a rationale. It
> would seem such packets should be masked somehow.

Actually, I think it is clearer to change all the y's in one function,
during parsing, rather than scattered about in various output
functions.

I'm sorry, I think I was misleading in my commit message.  This change
doesn't affect how packets get masked.  The y=0 is not handled
differently now that it is no longer inverted.  If it wasn't sent to
userspace before, it still won't be sent.

The older inverted y=0 was also, by definition, out of range, so
hopefully those packets are masked, and continue to be masked.  Not
inverting y=0 just makes it a bit easier to debug the driver, by
slightly more accurately parsing the incoming raw data.

>
> Thanks,
> Henrik
>
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