Re: [PATCH v3] add analog devices AD714X captouchinput driver

From: Mike Frysinger <vapier.adi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Barry Song <21cnbao-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>,
	uclinux-dist-devel-ZG0+EudsQA8dtHy/vicBwGD2FQJk+8+b@public.gmane.org,
	Dmitry Torokhov
	<dmitry.torokhov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"Hennerich,
	Michael"
	<Michael.Hennerich-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>,
	linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v3] add analog devices AD714X captouchinput driver
Date: Mon, 12 Oct 2009 13:08:23 -0400	[thread overview]
Message-ID: <8bd0f97a0910121008l1563803bu766e7d0868254a9f@mail.gmail.com> (raw)
In-Reply-To: <8bd0f97a0910101338y46cb227hdc6d83c3c6622a21-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Sat, Oct 10, 2009 at 16:38, Mike Frysinger wrote:
> On Fri, Oct 9, 2009 at 22:24, Barry Song wrote:
>> On Sat, Oct 10, 2009 at 12:22 AM, Dmitry Torokhov wrote:
>>> On Fri, Oct 09, 2009 at 06:11:45AM -0400, Mike Frysinger wrote:
>>>> On Fri, Oct 9, 2009 at 05:18, Mike Frysinger <vapier.adi@gmail.com> wrote:
>>>> > we could have three modules here: ad714x, ad714x-i2c, ad714x-spi
>>>>
>>>> are you ok with this approach Dmitry ?  this way people can
>>>> load/unload a specific bus without affecting the core or the other
>>>> bus, and errors with loading one bus type wouldnt affect loading of
>>>> the other.
>>>
>>> Yes, I think this is the most clean way.
>>
>> That will decrease the cohesion and increase coupling. It's tedious
>> for one driver with single feature to have three modules. To fulfill
>> that, ad714x need to expose data structures and export symbols to
>> ad714x-i2c and ad714x-spi. But those data structures and symbols are
>> more like local stuff. And I2C and SPI are just bottom level
>> communication ways, they should be the bottom level of ad714x, but
>> after splitting to 3 modules, it seems they become the top level of
>> ad714x.
>
> there should already be a clear split between the bus and the driver
> core, otherwise crap is being duplicated between the two interfaces.
> i just tested splitting things and each bus code needs to know very
> few things:
>  - probe/remove for initialization
>  - enable/disable for pm
>
> the only downside i see here is that we have to remove
> __devinit/__devexit markings from the common probe/remove functions
> and those weigh a hefty 2406/218 bytes a piece.

i spent time packing common stuff in the probe code and cut it down by
~1k, so i'm fine with this little bit of overhead.

Barry: can you test out the latest ad714x driver and make sure i didnt
screw anything up ?  i dont have any hardware to actually test these
guys out ...
-mike
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