Re: IIO_CONST_ATTR_SCAN_EL_TYPE add result shift?

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

On 10/05/10 12:52, Hennerich, Michael wrote:
> Jonathan Cameron wrote on 2010-10-05:
>> On 10/05/10 12:24, Hennerich, Michael wrote:
>>> /**
>>>  * IIO_CONST_ATTR_SCAN_EL_TYPE - attr to specify the data format of a
>>>  scan el * @name: the scan el name (may be more general and cover a set
>>>  of scan elements * @_sign: either s or u for signed or unsigned *
>>>  @_bits: number of actual bits occuplied by the value * @_storagebits:
>>>  number of bits _bits is padded to when read out of
>>> buffer  **/ #define IIO_CONST_ATTR_SCAN_EL_TYPE(_name, _sign, _bits,
>>> _storagebits) \
>>>         IIO_CONST_ATTR(_name##_type, #_sign#_bits"/"#_storagebits);
>>> There are cases where bits < storagebits and the result is not alligned
>>> to the LSB. Lets say we have an 10-bit ADC. The output is stored in a
>>> 16-bit word, with four leading zeros, then the 10-bit datum, followed
>>> by 2 don't care bits.
>>>
>>> So it would be good to provide an additional shift value?
>>> Or how shall we handle these cases?
>> This was discussed in the original debate and we simply proposed
>> leaving it until we had a user.  So the question is how to describe
>> the shift.
>>
>> So taking your example, how about:
>>
>> u10/16>>2
>>
>> Where the shift is optional.
>>
>> Other suggestions welcome given I made that up with 2 seconds thought.
> 
> I think this is sufficient. I can only think about right shifts being useful.
> This notation would consistently allow both, that's why I like it.
It would be decidedly odd for right shift to make sense.
> 
> A bit off topic - some common defines for signed/unsigned types might also be useful.
> 
> #define IIO_SCAN_EL_TYPE_SIGNED         's'
> #define IIO_SCAN_EL_TYPE_UNSIGNED       'u'
Fine with me.
> 
> Greetings,
> Michael
> 
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