Re: [PATCH 0/2] blue part 6: IIO abi rework

[Jonathan Cameron <jic23@cam.ac.uk>]

On 07/28/11 09:36, Michael Hennerich wrote:
> On 07/28/2011 10:36 AM, Jonathan Cameron wrote:
>> On 07/28/11 09:08, Hennerich, Michael wrote:
>>> Jonathan Cameron wrote on 2011-07-28:
>>>> On 07/27/11 15:41, Michael Hennerich wrote:
>>>>> On 07/26/2011 01:06 PM, Jonathan Cameron wrote:
>>>>>> On 07/26/11 11:52, Michael Hennerich wrote:
>>>>>>> On 07/26/2011 11:17 AM, Jonathan Cameron wrote:
>>>>>>>> On 07/26/11 10:01, Hennerich, Michael wrote:
>>>>>>>>> Jonathan Cameron wrote on 2011-07-25:
>>>>>>>>>> Michael pointed out the issues that not having an explicit
>>>>>>>>>> direction for channels was causing and the inconsistency of the
>>>>>>>>>> inX and outX channel naming we got from hmwon.
>>>>>>>>>>
>>>>>>>>>> They are stuck with it, but we aren't, so lets fix this now.
>>>>>>>>>>
>>>>>>>>>> Interesting question is whether we reset the base units to be
>>>>>>>>>> volts whilst we are at it? (for voltage channels obviously!)
>>>>>>>>> What do you mean exactly volts versus milli volts?
>>>>>>>> Make the in_voltage_scale correspond to conversion to volts instead
>>>>>>>> of millivolts as now (I think). Err. Looking at it that isn't
>>>>>>>> actually documented... oops.  I wonder which drivers actually do
>>>>>>>> that and which don't.
>>>>>>> The ones I wrote provide the scale for millivolts.
>>>>>>> With the recent introduction of IIO_VAL_INT_PLUS_NANO we got the
>>>>>>> scale accurate enough for the precession 24-bit converters.
>>>>>>> If we move to the SI base unit volt, we lose this accuracy again.
>>>>>> Yup, that's the principal counter argument to the change.
>>>>> If we decide to leave the milli scale for volts... Do we also want to
>>>>> stay with milli degrees Celsius, etc.? If we do it for one, probably
>>>>> best to do it for them all..
>>> Hi Jonathan,
>>>
>>> So stick with the milli scale for all?
>> Yes.
>>>>> One other thing we should also address is the
>>>>> byte-ordering/endianess of the scan elements stored in the ring buffers.
>>>>>
>>>>> Right now the scan_element type details signs, bits, storage bits and
>>>>> shifts. However it lacks to tell the endianess within the storage bits.
>>>>> Good point. I'd completely forgotten about that.
>>>>>
>>>>> How about le:s16/32>>0 or be:s16/32>>0 for example?
>>>> Yup, that works for me.  In cases where it doesn't matter they driver
>>>> can pick one at random.
>>>
>>> We need another case - Some drivers use the (be|le)(x)_to_cpu() helpers,
>>> So in case these are used the endianess can be either or, depending on the host.
>>> So maybe have le|be|cpu?
>> I thought about that, but am inclined to say we just stop drivers doing the conversion.
>> Better to leave it up to userspace?
> Well - we have and definitely will have more drivers where the conversion may be
> to time consuming to do in kernel space.
> I really don't have a strong preference here - but the important thing is that we need
> to tell user space what format is placed into the buffers.
Agreed. Do it during move out of staging or do a mass push to the drivers now?