linux-kernel - Re: [PATCH 05/12] Input: synaptics - process button bits in AGM packets

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Message-ID: <4E1355CB.9070504@canonical.com>
Date:	Tue, 05 Jul 2011 11:19:55 -0700
From:	Chase Douglas <chase.douglas@...onical.com>
To:	Henrik Rydberg <rydberg@...omail.se>
CC:	Daniel Kurtz <djkurtz@...omium.org>, dmitry.torokhov@...il.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 05/12] Input: synaptics - process button bits in AGM packets

On 07/05/2011 11:18 AM, Henrik Rydberg wrote:
>>> Any particular reason to move these and leave them unassigned for clickpads?
>>
>> Yes.  The current implementation incorrectly parses the x, y, z of AGM
>> packets and assigns junk values to the corresponding fields of the
>> temporary hw struct.  Luckily, this struct is then just discarded upon
>> return (synaptics_parse_hw_state returns 1 causing
>> synaptics_process_packet() to exit immediately).
>>
>> Instead, this patch parses the w value first to determine the packet
>> type, and then use this packet type information to parse the remaining
>> position and pressure fields correctly...
>>
>> Notice that the "else" clause is taken for SGM packets (w != 2), even
>> for clickpads.
> 
> Functionally, there is no difference between assigning new junk or
> reusing old junk, hence that part of the patch is not strictly needed.

True, it's not necessary, but I do like the new flow better. I was
reviewing the patch myself when I started wondering why we ever assigned
junk that was incorrect. I think this will help clean up the code and
make it more readable.

-- Chase
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