Re: [PATCH] iio: frequency: New driver for Analog Devices ADF4350/ADF4351 Wideband Synthesizers

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

On 06/03/2013 09:18 AM, Michael Hennerich wrote:
> On 05/11/2012 09:41 AM, Michael Hennerich wrote:
>> On 05/10/2012 02:36 PM, Jonathan Cameron wrote:
>>> On 5/8/2012 4:34 PM, Michael Hennerich wrote:
>>>> On 05/08/2012 04:51 PM, Jonathan Cameron wrote:
>>>>> On 5/7/2012 2:49 PM, michael.hennerich@analog.com wrote:
>>>>>> From: Michael Hennerich<michael.hennerich@analog.com>
>>>>>>
>>>>>>
>>>>>> +
>>>>>> +static const struct iio_chan_spec_ext_info adf4350_ext_info[] = {
>>>>>> + /* Ideally we use IIO_CHAN_INFO_FREQUENCY, but there are
>>>>>> + * values>  2^32 in order to support the entire frequency range
>>>>>> + * in Hz. Using scale is a bit ugly.
>>>>>> + */
>>>>> hmm.. Add IIO_VAL_MEGA_PLUS_INT.. We were always going to need a bigger
>>>>> version at somepoint...
>>>> Well - we then need an s64, however read|write_raw feature s32 for
>>>> val and val2. So shall we pass low word in val and high word in val2?
>>> I was thinking
>>> val*1e6 + val2 would fit with what we have done elsewhere?  Is that
>>> enough room?
>> Hi Jonathan,
>>
>> IIO_VAL_MEGA_PLUS_INT versus IIO_VAL_LONG_LONG
>>
>> It is enough room. But I wonder why we would do costly divide and modulus operations, when we can do sifts and ANDs?
>> Splitting a s64 would give is the maximum available room with very little overhead.
>>
>> Thoughts?
> 
> Hi Jonathan,
> 
> I like to touch base on the IIO_VAL_MEGA_PLUS_INT versus IIO_VAL_LONG_LONG thing again.
> We need something bigger as IIO_VAL_INT without loosing granularity by using scale.
> 
> You're favorite is still IIO_VAL_MEGA_PLUS_INT?
Yes, for consistency with the existing interfaces.

> I need to implement something - just like to get everyones thought again.
>