linux-kernel - Re: [PATCH 1/2] dt-bindings: thermal: correct thermal zone node name limit

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Date: Wed, 3 Jan 2024 17:29:30 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Rob Herring <robh+dt@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Liviu Dudau <liviu.dudau@....com>,
 Sudeep Holla <sudeep.holla@....com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Amit Kucheria <amit.kucheria@...aro.org>, linux-pm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: thermal: correct thermal zone node name
 limit

On 03/01/2024 16:12, Rob Herring wrote:
> On Wed, Jan 3, 2024 at 7:20 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>>
>> Linux kernel uses thermal zone node name during registering thermal
>> zones and has a hard-coded limit of 20 characters, including terminating
>> NUL byte.  The bindings expect node names to finish with '-thermal'
>> which is eight bytes long, thus we have only 11 characters for the reset
>> of the node name, not 12.
>>
>> Reported-by: Rob Herring <robh@...nel.org>
>> Closes: https://lore.kernel.org/all/CAL_JsqKogbT_4DPd1n94xqeHaU_J8ve5K09WOyVsRX3jxxUW3w@mail.gmail.com/
>> Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for thermal zones")
>> Cc: <stable@...r.kernel.org>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> ---
>>  Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> index 4a8dabc48170..bbc883fd4044 100644
>> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> @@ -49,7 +49,7 @@ properties:
>>        to take when the temperature crosses those thresholds.
>>
>>  patternProperties:
>> -  "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
>> +  "^[a-zA-Z][a-zA-Z0-9\\-]{1,11}-thermal$":
> 
> Now off by 1 instead of 2. It should be 1 starting char, 1-10 chars,
> and 8 chars for "-thermal".

Why off by 2? prefix can be up to 11 bytes, plus 8 bytes for "-thermal"
and 1 byte for NUL. This gives 11+8+1=20, exactly the size used in Linux
kernel.

> 
> Can you also add a comment that this length is due to the kernel.

Sure

Best regards,
Krzysztof