Re: STMicroelectronics accelerometers driver.

[Jonathan Cameron <jic23@kernel.org>]

On 10/31/2012 04:40 PM, Lars-Peter Clausen wrote:
> Hi,
> 
> On 10/31/2012 03:27 PM, Denis CIOCCA wrote:
>> Hi Lars-Peter,
>>
>> I'm trying modified the driver to change the fullscale attribute and use 
>> the in_accel_*_scale attribute.
>> My question is that:
>>
>> - the in_accel_*_scale attribute rappresent the conversion value from 
>> raw data sensor to m/s2, if I use only this value, how can I know what 
>> is the maximum full scale associated to the value?
> 
> Unfortunately there is currently no way in IIO to specify minimum or maximum
> values for a given channel. But you are welcome to come up with one, I think
> this will be useful for other drivers as well.
My personal preference would be an additional (for now optional) callback
alongside read_raw and write_raw called something like available.  This would
be used by additional xxxxx_available attributes to describe the possible
values for info_mask element.  Exactly how to do this cleanly is a small
'implemention detail' which means this will probably be rather more
complex than this implies :)

Interdependent info_mask elements will be 'interesting' (say a scale
attribute for which the possible values change with the sampling frequency or
visa-versa).

I've been meaning to look at this for a while, but if anyone else fancies
giving it a go, feel free!
> 
>>
>> - how can I view a list of available values? I have to create scale 
>> attribute on sysfs? If the last point is true, it is so redundant what I 
>> did before?
> 
> You should add a scale_available attribute. Some ADC drivers implement this,
> you could use them as an example.
> 
> - Lars
> 
>>
>>
>> Thanks,
>>
>> Denis
>>
>>
>> On 10/29/2012 11:30 AM, Lars-Peter Clausen wrote:
>>> On 10/29/2012 11:24 AM, Denis CIOCCA wrote:
>>>>
>>>>> There is no attachment attached to this mail.
>>>> my was a question. You prefer I attach all source code or the last modified?
>>>>
>>>>
>>>>>> I don't find IIO_G_TO_M_S_2 in the framework code, but I added this
>>>>>> macro in my source code. It is exatly?
>>>>>
>>>>> It's in the latest IIO tree and also in staging/staging-next. The definition is
>>>>>
>>>>> +#define IIO_DEGREE_TO_RAD(deg) (((deg) * 314159ULL + 9000000ULL) \
>>>>> 	/ 18000000ULL)
>>>>
>>>> Sorry but I'm lost. The relation from IIO_DEGREE_TO_RAD and IIO_G_TO_M_S_2?
>>>>
>>>
>>> Sorry, too early in the morning, copied the wrong line.
>>>
>>> +#define IIO_G_TO_M_S_2(g) ((g) * 980665ULL / 100000ULL)
>>>
>>> Btw. the full patch can be found here:
>>>   http://comments.gmane.org/gmane.linux.kernel.iio/5777
>>>
>>> - Lars
>>>
>