[PATCH 1/3] dt-bindings: iio: adc: stm32: add support for diff channels

On Sat, 21 Oct 2017 18:54:01 +0100
Jonathan Cameron [off-list ref] wrote:

On Tue, 17 Oct 2017 15:15:43 +0200
Fabrice Gasnier [off-list ref] wrote:

quoted

STM32H7 ADC channels may be configured either as single-ended or
differential.
Add 'st,adc-diff-channels' property to support differential channels.
Differential channels are defined as a pair of positive and negative
inputs: vinp & vinn.

Signed-off-by: Fabrice Gasnier <redacted>  

Hmm. Fair enough.  Sometimes we support both types of channels
and leave it to userspace, but in many cases that makes little sense
- particularly if like I think is going on here, we aren't combining channels
that can be separately read but rather the negative pin is simply unused
when we are in single channel mode... (did I understand that right?)

I clearly didn't understand.  This is same as other devices
in that we are picking a pair from the channels that can otherwise be
used as single end channels. (I think). 

For this binding I think I'd like to see an example added showing how
this works...

Thanks,

Jonathan

Jonathan

quoted

---
 Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
index 48bfcaa3..c3c8de1 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt

@@ -62,6 +62,12 @@ Required properties:
 - st,adc-channels: List of single-ended channels muxed for this ADC.
   It can have up to 16 channels on stm32f4 or 20 channels on stm32h7, numbered
   from 0 to 15 or 19 (resp. for in0..in15 or in0..in19).
+- st,adc-diff-channels: List of differential channels muxed for this ADC.
+  Depending on part used, some channels can be configured as differential
+  instead of single-ended (e.g. stm32h7). List here positive and negative
+  inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered
+  from 0 to 19 on stm32h7)
+  Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is required.
 - #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
   Documentation/devicetree/bindings/iio/iio-bindings.txt
   

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