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

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 08 May 2026 18:00:25 +0100
Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:

> From: Rodrigo Alencar <rodrigo.alencar@analog.com>
> 
> 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@analog.com>
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@vger.kernel.org
> +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
 
> +KernelVersion:
> +Contact:	linux-iio@vger.kernel.org
> +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.