Re: [PATCH v2 1/2] dt-bindings: staging: iio: cdc: ad7746: add binding documentation for AD7746

From: Lars-Peter Clausen
Date: Thu Apr 22 2021 - 16:56:46 EST

On 4/22/21 9:16 PM, Lucas Stankus wrote:
On Tue, Apr 20, 2021 at 4:37 PM Rob Herring <robh@xxxxxxxxxx> wrote:
On Sun, Apr 18, 2021 at 07:49:51PM -0300, Lucas Stankus wrote:
Add device tree binding documentation for AD7746 cdc in YAML format.

Signed-off-by: Lucas Stankus <lucas.p.stankus@xxxxxxxxx>

A minor note about the adi,excitation-vdd-permille property. Jonathan
suggested the name to be adi,excitation-vdd-milicent, but I was unsure of
the milicent naming. With a quick search I found out that the common way to
call a thousandth is 'per mille'[1], but I didn't find any use of it in the
kernel documentation. Any thoughts about it?
Seems okay to me.


.../bindings/iio/cdc/adi,ad7746.yaml | 73 +++++++++++++++++++
1 file changed, 73 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml

diff --git a/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
new file mode 100644
index 000000000000..a2a7eee674ba
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
@@ -0,0 +1,73 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+title: AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
+ - Michael Hennerich <michael.hennerich@xxxxxxxxxx>
+description: |
+ AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
+ Specifications about the part can be found at:
+ compatible:
+ enum:
+ - adi,ad7745
+ - adi,ad7746
+ - adi,ad7747
+ reg:
+ maxItems: 1
+ adi,excitation-vdd-permille:
+ description: |
+ Set VDD per mille to be used as the excitation voltage.
+ $ref: /schemas/types.yaml#/definitions/uint32
+ enum: [125, 250, 375, 500]
+ adi,exca-output-en:
+ description: Enables the EXCA pin as the excitation output.
+ type: boolean
+ adi,exca-output-invert:
+ description: Inverts the excitation output in the EXCA pin.
+ type: boolean
'invert' assumes I know what the non-inverted signal is. Sometimes that
makes sense, but if you can define in terms of the inverse that would be
better. For example, for a normally active low signal, name the property
Thanks for the feedback!
From reading the data sheet I couldn't quite grasp what would be an inverted
excitation output, but I don't have a lot of experience with CDCs. Maybe someone
with more experience could help out with a better suggestion.

This is the only thing I could find

The datasheet also says that only at most one of them should be inverted. So maybe only a single property which selects which of the two is inverted.