Re: [PATCH RFC v3 9/9] docs: iio: add documentation for ad9910 driver

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 27 Apr 2026 15:54:14 +0100
Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote:

> On 26/04/27 11:31AM, Nuno Sá wrote:
> > On Mon, Apr 27, 2026 at 10:46:08AM +0100, Jonathan Cameron wrote:  
> > > On Sun, 26 Apr 2026 21:42:15 +0100
> > > Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote:
> > >   
> > > > On 26/04/26 02:10PM, Jonathan Cameron wrote:  
> > > > > On Fri, 17 Apr 2026 09:17:38 +0100
> > > > > Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:
> > > > >     
> > > > > > From: Rodrigo Alencar <rodrigo.alencar@analog.com>
> > > > > > 
> > > > > > Add documentation for the AD9910 DDS IIO driver, which describes channels,
> > > > > > DDS modes, attributes and ABI usage examples.
> > > > > > 
> > > > > > Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>    
> > > > > 
> > > > > Hi Rodrigo,
> > > > > 
> > > > > I think this is getting close to something workable subject to some tweaks
> > > > > to not make the priority thing visible and use rate of change parameters
> > > > > so /Sec rather than steps.    
> > > > 
> > > > I am not sure about this one. Getting the value into units per seconds will
> > > > increase the range of values by a lot, e.g., for the frequency case the step
> > > > size can range from a few Hz up to the entire supported range (hundreds of
> > > > MHz), and if you consider that one would often have the sampling_frequency
> > > > at 250 MHz... an attribute frequency_roc could have an order of 10^17 Hz/s,
> > > > and I am not sure how practical is that, although it can have a physical meaning,
> > > > like a "chirp slope".  
> > > 
> > > That scaling is indeed a bit of a pain though it will go in a 64 bit int
> > > however, seems likely we'll get higher frequency devices one day that will
> > > limb even faster.
> > > 
> > > Maybe wait and see if anyone else has input on this.	  
> > 
> > If we think things like RF DACs (which internally - typically - make use
> > of things like DDS), we can already go to the GHz "world".
> > 
> > Not saying we already have such a device that would map the new ABI with
> > bigger values (we might have but nothing I'm aware of from the top of my
> > head) but just saying the above is, indeed, very likely to pop up at some
> > time.
> > 
> > Just something to bear in mind :)
> > 
> > - Nuno Sá  
> 
> under this Documentation/ABI/testing/sysfs-bus-iio-impedance-analyzer-ad5933,
> there is ABI: /sys/bus/iio/devices/iio:deviceX/out_altvoltageY_frequency_increment
> 
> which seems to be a similar concept to the step used here.

Yeah but staging driver so let's not focus on that too much.

>