Re: [PATCH] iio: chemical: atlas-ph-sensor: switch regmap cache

[Jonathan Cameron <jic23@kernel.org>]

On 17/02/16 21:44, Matt Ranostay wrote:
> On Wed, Feb 17, 2016 at 1:19 PM, Jonathan Cameron <jic23@kernel.org> wrote:
>> On 15/02/16 15:02, Mark Brown wrote:
>>> On Sun, Feb 14, 2016 at 06:40:15PM +0100, Lars-Peter Clausen wrote:
>>>> On 02/14/2016 04:02 PM, Jonathan Cameron wrote:
>>>
>>>>> I'm lost here. Why should changing the storage of the register cache result
>>>>> in different behaviour other than in efficiency of access to cached values?
>>>
>>>> And if there is really a difference this should probably be addressed at the
>>>> regmap level.
>>>
>>> You'd need to make regcache-flat keep track of which cache values are
>>> valid either during init (in which case it'd have to read every other
>>> register at that time) or at runtime (which would mean extra operations
>>> in a fast path).  Flat really is special here, there's no reason to use
>>> it over a rbtree other than being very sensitive about performance.
>>>
>>> Please also be aware that if you CC me on an iio patch series there's a
>>> good chance I'll just delete it without reading it, for some reason I
>>> keep on getting copied on lots of them which have no relevance to me
>>> that I'm able to identify.
>>>
>> Hmm.  Not the best documented 'non intuitive case' ever, but fair enough.
>> Glad you did pick this one up Mark!
>>
>> So Matt, the reason those two elements are dropped from being volatile
>> is that they never were, but because we were using a flat cache it wasn't
>> getting the original values?
>>
>> If so fair enough I suppose, but please confirm that I've understood this
>> correctly + I'll probably expand the patch description somewhat to make it
>> clearer why the original was wrong.
> 
> That is correct. Flat cache wasn't getting the on device value without
> it being set as volatile.
Applied to the togreg branch iio.git - initially pushed out as testing
for the autobuilders to play with it.

Thanks,
Jonathan
> 
> 
>>
>> Jonathan
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