linux-kernel - Re: Blockers on IIO usage of regmap.

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Date:	Wed, 07 Sep 2011 19:12:37 +0100
From:	Jonathan Cameron <jic23@....ac.uk>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	"Hennerich, Michael" <Michael.Hennerich@...log.com>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: Re: Blockers on IIO usage of regmap.

On 09/07/11 18:57, Mark Brown wrote:
> On Wed, Sep 07, 2011 at 05:10:24PM +0100, Jonathan Cameron wrote:
> 
> Please fix your mailer to word wrap at less than 80 colums, they're
> really quite hard to read as a result of this.
> 
>> CS -_______________________-
>> TX  Ada0...Ada7  Da0....Da7
>> RX XXXXXXXXXXXXXXXXXXXXXXXXX
>>
>> Reads are 16 bit with either of the two 8 bit register addresses given the same value
>>
>> CS -______________________-_____________________-
>> TX  Ada0....Ada7 XXXXXXXX
>> RX  XXXXXXXXXXXXXXXXXXXXX  Da0...Da7  Db0....Db7  
> 
>> Can interpret Da0...Da7 and Db0....Db7 as single 16 bit register and consider this device
>> to just have a weird write method and normal read.  Might be easier.  I'll define Ax<n> as
>> 16 bit address for the burst read.
> 
> This is starting to seem pretty far off the reservation.
Indeed.
> 
>> Perhaps the burst mode thing is better handled by just providing a hook to allow data to be pushed
>> into regmap (from 'magic' sources), but the weird write read combination looks to me like something
>> that makes sense to have in regmap (be it as another bus variant).
> 
> Probably not as a bus, it sounds like a marshalling difference rather
> than a bus - the buses should really only understand byte streams.  I
> don't have any bright ideas on how to deal with this, it's fairly far
> away from the problem space I'm worried about.
The right answer maybe that it isn't a good idea to do it at all, but it
wasn't obvious until I tried! Having done it I'm not sure either way.

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