Re: Accessing specific hardware features of mxs-lradc

[Alexandre Belloni <alexandre.belloni@free-electrons.com>]

On 02/07/2013 14:58, Lars-Peter Clausen wrote:
> On 07/02/2013 12:49 PM, Hector Palacios wrote:
>> Greetings,
>>
>> The mxs-lradc has some hardware specific features like the DIVIDE_BY_TWO (an
>> analog divide by two circuit that can be activated per channel).
>> This is not currently implemented in the driver and I was wondering what would
>> be the way to expose and control such setting. A specific sysfs entry? Somehow
>> through the device tree?
>>
>> Is there any example of how to control a hw-specific feature in other similar
>> iio drivers?
>>
> 
> This sounds as if the channel scale is programmable. There are quite a few
> drivers for devices which have similar features, just make the scale property
> writable and provide a scale_available.
> 

I was looking at that yesterday as I had to had a scale for the
temperature sensors. You'll have to be careful because the maximum
measured voltage when DIVIDE_BY_TWO is not set is 1.85V and when it is
set, it becomes VDDIO - 50mv.

Also, scaling for quite a lot of channels is fixed. You'll also get
channels with a fixed divider that can take DIVIDE_BY_TWO. That is quite
a mess ;)

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com