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([2600:8803:e7e4:500:d4c1:7681:5df:9500]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-44cbe84f609sm1119946fac.1.2026.07.01.15.07.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Jul 2026 15:07:10 -0700 (PDT) Message-ID: Date: Wed, 1 Jul 2026 17:07:09 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/8] dt-bindings: iio: adc: Add excitation current sources properties To: Jonathan Cameron Cc: =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Chris Hall , Patrick Edwards , Kurt Borja , Nguyen Minh Tien , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260625-iio-adc-ti-ads122c14-v2-0-ceb9b0b561cb@baylibre.com> <20260625-iio-adc-ti-ads122c14-v2-2-ceb9b0b561cb@baylibre.com> <20260701203932.20e688db@jic23-huawei> Content-Language: en-US From: David Lechner In-Reply-To: <20260701203932.20e688db@jic23-huawei> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/1/26 2:39 PM, Jonathan Cameron wrote: > On Thu, 25 Jun 2026 16:55:04 -0500 > David Lechner wrote: > >> From: Kurt Borja >> >> Some ADCs incorporate current sources that provide excitation current to >> resistive temperature devices (RTDs), thermistors, diodes and other >> resistive sensors that require constant current biasing. >> >> Signed-off-by: Kurt Borja >> Signed-off-by: David Lechner (TI) >> --- >> v2 changes (compared to Kurt's RFC v2): >> * Make units nanoamps instead of microamps to fit known devices. >> * Drop bit about allowing single value for multiple channels. >> * Add bit about semantics of the array index. >> --- >> Documentation/devicetree/bindings/iio/adc/adc.yaml | 20 ++++++++++++++++++++ >> 1 file changed, 20 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/iio/adc/adc.yaml b/Documentation/devicetree/bindings/iio/adc/adc.yaml >> index 12800737d4fb..860601ec5334 100644 >> --- a/Documentation/devicetree/bindings/iio/adc/adc.yaml >> +++ b/Documentation/devicetree/bindings/iio/adc/adc.yaml >> @@ -81,6 +81,26 @@ properties: >> ADCs usually allow choosing between internal reference sources or a pair >> of external pins. >> >> + excitation-channels: > > How would this apply if a device provided excitation on pins that didn't correspond > to channels? i.e. some extra ones. Perhaps such a device that also supports > configuration (rather than a static set up) would just need a different binding. > Feels like I'm creating a corner case we may never see :) > We could have e.g. a ti,current-output flag to say that this is just a current output channel if we really needed this. In that case, I think we would use single-channel to specify the pin and not have excitation-channels or excitation-current-nanoamp. But as you guessed, this not something we would expect anyone to actually do with these chips, so we'll leave that out.