Re: [PATCH v3] iio: temperature: add support for Maxim thermocouple chips

[Lars-Peter Clausen <lars@metafoo.de>]

On 06/11/2016 06:48 PM, Jonathan Cameron wrote:
> On 03/06/16 13:33, Jonathan Cameron wrote:
>> On 30/05/16 02:37, Matt Ranostay wrote:
>>> Add initial driver support for MAX6675, and MAX31885 thermocouple chips.
>>>
>>> Cc: Marek Vasut <marex@denx.de>
>>> Cc: Matt Porter <mporter@konsulko.com>
>>> Signed-off-by: Matt Ranostay <mranostay@gmail.com>
>> I'm going to let this sit for a sort while as I'd like some discussion
>> of the invalidate buffer bit.
>>
>> Cc'd a few more people for views.
> Hmm. Deadly silence.
> 
> Daniel, Lars, Peter - this is a fairly fundamental abi question.
> 
> What do we do to signify an 'invalid reading' in the buffer.
> 
> Here the part is driven by a software trigger - and if we skip
> a reading we are obviously out of sync.
> 
> Old and nasty trick we used in some (possibly only one)
> early driver was to set an invalid state for these cases.
> 
> Anyone have a better idea?

Ideally the driver would leave the data including the status bit intact and
not replace it with a magic constant that way an application that is aware
of the way the chip behaves could handle that.