Re: [PATCH 3/3] Documentation: ABI: adl8113: add documentation

[Jonathan Cameron]

On Fri, 31 Oct 2025 16:04:05 +0000
Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx> wrote:

> Add ABI documentation for the ADL8113 Low Noise Amplifier,
> covering the 4 pin-selectable operating modes.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx>
> ---
>  .../testing/sysfs-bus-iio-amplifiers-adl8113  | 32 +++++++++++++++++++
>  1 file changed, 32 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113 b/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113
> new file mode 100644
> index 000000000000..6155b79e6b83
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113
> @@ -0,0 +1,32 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/mode
> +Date:		January 2025
> +KernelVersion:	6.14
> +Contact:	linux-iio@xxxxxxxxxxxxxxx
> +Description:
> +		This attribute allows the user to set the operation mode of the
> +		ADL8113 Low Noise Amplifier. The available modes control signal
> +		routing through different paths within the device.
> +
> +		The supported modes are:
> +
> +		* internal_amplifier - Signal passes through the internal low
> +		  noise amplifier (VA=0, VB=0). Provides 14dB gain.
> +
> +		* internal_bypass - Signal bypasses through internal bypass path
> +		  (VA=1, VB=1). Provides 0dB gain.

These first would map fine to standard ABI for gain control I think.
I'd prefer to see that used if possible than invention of new ABI for that.

> +
> +		* external_bypass_a - Signal routes through external bypass path A
> +		  (VA=0, VB=1). Provides 0dB gain.

Problem with this an next one as I mention in binding is we have no idea what
is between those two external pins so no way to present a generic userspace interface.

Any idea if there is anything that is standard to wire in there?  I could see for instance
nesting a similar amplifier to this one with different gain.  Maybe we should have
a go at describing that.  This device would be a consumer of channels provided by
another etc.

> +
> +		* external_bypass_b - Signal routes through external bypass path B
> +		  (VA=1, VB=0). Provides 0dB gain.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/mode_available
> +Date:		January 2025
> +KernelVersion:	6.14
> +Contact:	linux-iio@xxxxxxxxxxxxxxx
> +Description:
> +		Reading this attribute returns a space-separated list of all
> +		available operation modes for the ADL8113 device. The modes
> +		control the signal path and determine whether the signal passes
> +		through the internal amplifier or various bypass paths.