linux-kernel - Re: [PATCH v21 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs and transfer-mode properties

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Message-ID: <93a2ff5f-2f8e-494b-9652-b93bc243c229@kernel.org>
Date: Mon, 27 Oct 2025 20:14:45 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ryan Chen <ryan_chen@...eedtech.com>, bmc-sw@...eedtech.com,
 benh@...nel.crashing.org, joel@....id.au, andi.shyti@...nel.org,
 jk@...econstruct.com.au, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, andrew@...econstruct.com.au, p.zabel@...gutronix.de,
 andriy.shevchenko@...ux.intel.com, naresh.solanki@...ements.com,
 linux-i2c@...r.kernel.org, openbmc@...ts.ozlabs.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v21 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add
 global-regs and transfer-mode properties

On 27/10/2025 07:12, Ryan Chen wrote:
> The AST2600 I2C controller supports three transfer modes: byte,
> buffer, and DMA. To allow board designers and firmware to
> explicitly select the preferred transfer mode for each controller
> instance. "aspeed,transfer-mode" to allow device tree to specify
> the desired transfer method used by each I2C controller instance.
> 
> And AST2600 i2c controller have two register mode, one is legacy
> register layout which is mix controller/target register control
> together, another is new mode which is separate controller/target
> register control.
> 

This implies your "reg" properties have now completely different meaning
and this would be quite an ABI break. We discussed this probably 15
revisions ago. Where did you document the resolution of that discussion?

>  
>  unevaluatedProperties: false
>  
> @@ -57,10 +85,12 @@ examples:
>        #address-cells = <1>;
>        #size-cells = <0>;
>        compatible = "aspeed,ast2600-i2c-bus";
> -      reg = <0x40 0x40>;
> +      reg = <0x80 0x80>, <0xc00 0x20>;

Not relevant to this patch. You just added this line in patch #1, so did
you add incorrect code just to fix it right away?

No, fix your example when creating it.


Best regards,
Krzysztof