linux-kernel - Re: [PATCH 2/6] regmap: Add a magic bus type to handle quirks of analog devices ADIS sensors.

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Message-ID: <4E67BCDF.3020108@cam.ac.uk>
Date:	Wed, 07 Sep 2011 19:50:07 +0100
From:	Jonathan Cameron <jic23@....ac.uk>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	linux-kernel@...r.kernel.org, Michael.Hennerich@...log.com,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH 2/6] regmap: Add a magic bus type to handle quirks of
 analog devices ADIS sensors.

On 09/07/11 19:32, Mark Brown wrote:
> On Wed, Sep 07, 2011 at 07:26:10PM +0100, Jonathan Cameron wrote:
>> On 09/07/11 18:47, Mark Brown wrote:
>>> On Wed, Sep 07, 2011 at 05:19:43PM +0100, Jonathan Cameron wrote:
> 
>>> To be honest I'm not terribly happy about
>>> pushing this into the regmap core code; if we start needing to do stuff
>>> like this we should expose the bus interface.
> 
>> That's certainly an option, but I'd really like to use the regmap caching
>> stuff in here.  These things can have quite a few registers that other than
>> their weird read / write quirks look much like any other register based
>> device. (particularly ignoring the burst reads but they tend to apply
>> to volatile registers only so caching is probably irrelevant).
> 
>> At the moment, the only hooks AFAIKS to allow this are at the bus level.
>> I'm not sure where else they could go. (I haven't actually looked much
>> at the cache code yet though).
> 
> Well, if there's not hooks they could be added if it's not too painful.
> However I'm not convinced that's sane.
> 
>> Actually I may have misunderstood, do you mean expose the bus interface
>> within regmap or just not use regmap at all?
> 
> Either.  Or either expose marshalling or add configuration for the
> marshalling depending on what's being done, I'm not convinced you need
> to be working at SPI level at all.
I'm a little unclear what you mean by 'marshalling'.  Could you expand
on how that might work?
> 
>>>> +static struct regmap_bus regmap_spi_adi = {
>>>> +	.write = regmap_spi_write,
>>>> +	.read = regmap_spi_read,
>>>> +};
> 
>>> You want to implement the gather write too if you can.
> 
>> Doesn't really exist other than by linearising them into a series
>> of calls to the write function. (assuming I understand what those
>> functions are doing right!)
> 
> If you build up a series of SPI transfers you just need to control when
> /CS gets bounced appropriately.
Sure, might be worth doing.  To be honest I don't really care about writes
as these are write rarely read often devices other than single register
writes to clear interrupts (even that is often a read).
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