Re: [PATCH RFC v4 09/10] Documentation: ABI: testing: add docs for ad9910 sysfs entries

[Jonathan Cameron]

On Sun, 17 May 2026 15:58:43 +0100
Jonathan Cameron <jic23@xxxxxxxxxx> wrote:

> On Fri, 08 May 2026 18:00:25 +0100
> Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@xxxxxxxxxx> wrote:
> 
> > From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
> > 
> > Add custom ABI documentation file for the DDS AD9910 with sysfs entries to
> > control Parallel Port, Digital Ramp Generator and OSK parameters.
> > 
> > Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>  
> I'm fine with phase and frequency as defined, but for the scaling it made me wonder.
> For outvoltage0 channels the assumption the value is the peak voltage so if
> we know what input to be modulated by the ramp generator can we express them
> in volts (well milivolts) rather than as a scaling multiplier?
> 
> That seems to me like it fits better with the overall ABI.
> 
> > +What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_scale_offset
> > +KernelVersion:
> > +Contact:	linux-iio@xxxxxxxxxxxxxxx
> > +Description:
> > +		For a channel that allows amplitude control through buffers, this
> > +		represents the value for a base amplitude scale. The actual output
> > +		amplitude scale is a result with the sum of this value.
> > +  
> 
> > +
> > +What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_scale_roc  
> 
> Silly question perhaps but can work out how this related to millivolts/sec
> That might make a more intuitive interface than scaling multiplier per sec
> Perhaps the combination with offset makes this impossible though maybe that
> could be a expressed as a voltage offset?  Afterall if the amplitude being
> scaled is 5V then 5 * (offset + scale) = 5 * offset + 5 * scale
>  
See thread on next patch. I think I argued myself out of this.  

> > +KernelVersion:
> > +Contact:	linux-iio@xxxxxxxxxxxxxxx
> > +Description:
> > +		Amplitude scale rate of change in 1/s for channels that ramp
> > +		amplitude. This value may be influenced by the channel's
> > +		sampling_frequency setting.  
> 
> 
>