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([2600:8803:e7e4:1d00:fcf8:116:11db:fbac]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-61bebfb34f2sm488110eaf.10.2025.08.16.11.55.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 16 Aug 2025 11:55:32 -0700 (PDT) Message-ID: <66063382-78c6-4d93-be25-46e972e390f4@baylibre.com> Date: Sat, 16 Aug 2025 13:55:31 -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 1/5] dt-bindings: iio: mcp9600: Add compatible for microchip,mcp9601 To: Jonathan Cameron , Ben Collins Cc: =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Andrew Hepp , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250815164627.22002-1-bcollins@watter.com> <20250815164627.22002-2-bcollins@watter.com> <20250816105825.35e69652@jic23-huawei> Content-Language: en-US From: David Lechner In-Reply-To: <20250816105825.35e69652@jic23-huawei> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/16/25 4:58 AM, Jonathan Cameron wrote: > On Fri, 15 Aug 2025 16:46:03 +0000 > Ben Collins wrote: > >> The mcp9600 driver supports the mcp9601 chip, but complains about not >> recognizing the device id on probe. A separate patch... >> >> iio: mcp9600: Recognize chip id for mcp9601 >> >> ...addresses this. This patch updates the dt-bindings for this chip to >> reflect the change to allow explicitly setting microchip,mcp9601 as >> the expected chip type. >> >> The mcp9601 also supports features not found on the mcp9600, so this >> will also allow the driver to differentiate the support of these >> features. > > If it's additional features only then you can still use a fallback > compatible. Intent being that a new DT vs old kernel still 'works'. > > Then for the driver on new kernels we match on the new compatible and > support those new features. Old kernel users get to keep the ID > mismatch warning - they can upgrade if they want that to go away ;) > > Krzysztof raised the same point on v2 but I'm not seeing it addressed > in that discussion. One could make the argument that these are not entirely fallback compatible since bit 4 of the STATUS register has a different meaning depending on if the chip is MCP9601/L01/RL01 or not. Interestingly, the existing bindings include interrupts for open circuit and short circuit alert pins. But these pins also only exist on MCP9601/L01/RL01. If we decide these aren't fallback compatible, then those properties should have the proper constraints added as well. > > Jonathan > >> >> Signed-off-by: Ben Collins >> --- >> .../bindings/iio/temperature/microchip,mcp9600.yaml | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9600.yaml b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9600.yaml >> index d2cafa38a5442..d8af0912ce886 100644 >> --- a/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9600.yaml >> +++ b/Documentation/devicetree/bindings/iio/temperature/microchip,mcp9600.yaml >> @@ -4,7 +4,7 @@ >> $id: http://devicetree.org/schemas/iio/temperature/microchip,mcp9600.yaml# >> $schema: http://devicetree.org/meta-schemas/core.yaml# >> >> -title: Microchip MCP9600 thermocouple EMF converter >> +title: Microchip MCP9600 and similar thermocouple EMF converters >> >> maintainers: >> - Andrew Hepp >> @@ -14,7 +14,9 @@ description: >> >> properties: >> compatible: >> - const: microchip,mcp9600 >> + enum: >> + - microchip,mcp9600 >> + - microchip,mcp9601 >> >> reg: >> maxItems: 1 >