linux-kernel - Re: [PATCH v2 1/6] dt-bindings: Remove unused compatible strings

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Date:   Mon, 08 Jul 2019 23:18:19 -0400
From:   Paul Cercueil <paul@...pouillou.net>
To:     Rob Herring <robh@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Mark Rutland <mark.rutland@....com>, od@...c.me,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] dt-bindings: Remove unused compatible strings



Le lun. 8 juil. 2019 à 22:04, Rob Herring <robh@...nel.org> a écrit :
> On Fri, Jun 07, 2019 at 05:44:05PM +0200, Paul Cercueil wrote:
>>  Right now none of the Ingenic-based boards probe this driver from
>>  devicetree. This driver defined three compatible strings for the 
>> exact
>>  same behaviour. Before these strings are used, we can remove two of
>>  them.
>> 
>>  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>  ---
>> 
>>  Notes:
>>      v2: Rebase on v5.2-rc3
>> 
>>   Documentation/devicetree/bindings/pwm/ingenic,jz47xx-pwm.txt | 5 
>> +----
>>   1 file changed, 1 insertion(+), 4 deletions(-)
>> 
>>  diff --git 
>> a/Documentation/devicetree/bindings/pwm/ingenic,jz47xx-pwm.txt 
>> b/Documentation/devicetree/bindings/pwm/ingenic,jz47xx-pwm.txt
>>  index 7d9d3f90641b..493bec80d59b 100644
>>  --- a/Documentation/devicetree/bindings/pwm/ingenic,jz47xx-pwm.txt
>>  +++ b/Documentation/devicetree/bindings/pwm/ingenic,jz47xx-pwm.txt
>>  @@ -2,10 +2,7 @@ Ingenic JZ47xx PWM Controller
>>   =============================
>> 
>>   Required properties:
>>  -- compatible: One of:
>>  -  * "ingenic,jz4740-pwm"
>>  -  * "ingenic,jz4770-pwm"
>>  -  * "ingenic,jz4780-pwm"
>>  +- compatible: Should be "ingenic,jz4740-pwm"
> 
> Are you sure all 3 chips are exactly the same features and bugs?

The hardware on these chips have tiny differences, but the current
driver code works on all the SoCs.


> The correct thing to do here generally is the 4770 and 4780 would also
> have ingenic,jz4740-pwm as a fallback compatible. Then the driver can
> match on that until you find some difference and can use the more
> specific compatible.

Why not just update the devicetree with the new compatible string when
a difference is found?


>>   - #pwm-cells: Should be 3. See pwm.txt in this directory for a 
>> description
>>     of the cells format.
>>   - clocks : phandle to the external clock.
>>  --
>>  2.21.0.593.g511ec345e18
>>