linux-kernel - Re: [PATCH RFC 1/6] dt-bindings: dma: qcom,gpi: Retire passing the protocol ID

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Message-ID: <20250730234631.GA1899887-robh@kernel.org>
Date: Wed, 30 Jul 2025 18:46:31 -0500
From: Rob Herring <robh@...nel.org>
To: Konrad Dybcio <konradybcio@...nel.org>
Cc: Vinod Koul <vkoul@...nel.org>, Sven Peter <sven@...nel.org>,
	Janne Grunau <j@...nau.net>,
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	Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH RFC 1/6] dt-bindings: dma: qcom,gpi: Retire passing the
 protocol ID

On Wed, Jul 30, 2025 at 11:33:28AM +0200, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> 
> This is a software construct that has no business being expressed in
> dt-bindings. Drivers can be constructed to retrieve the protocol ID at
> runtime or hardcode them per protocol.
> 
> Remove it, as a pre-requisite for further simplifying the GENI
> bindings.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> ---
>  Documentation/devicetree/bindings/dma/qcom,gpi.yaml | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/qcom,gpi.yaml b/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
> index bbe4da2a11054f0d272017ddf5d5f7e47cf7a443..745613b93b210afd38946030f7477e91e08c907a 100644
> --- a/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
> +++ b/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
> @@ -61,14 +61,13 @@ properties:
>      maxItems: 13
>  
>    "#dma-cells":
> -    const: 3
> +    const: 2

I think you need to keep 3 and note it is deprecated. Does an existing 
kernel support this being 2 already. If not, ABI break...

>      description: >
>        DMA clients must use the format described in dma.txt, giving a phandle
>        to the DMA controller plus the following 3 integer cells:
>        - channel: if set to 0xffffffff, any available channel will be allocated
>          for the client. Otherwise, the exact channel specified will be used.
>        - seid: serial id of the client as defined in the SoC documentation.
> -      - client: type of the client as defined in dt-bindings/dma/qcom-gpi.h
>  
>    iommus:
>      maxItems: 1
> @@ -98,7 +97,7 @@ examples:
>      #include <dt-bindings/dma/qcom-gpi.h>
>      gpi_dma0: dma-controller@...000 {
>          compatible = "qcom,sdm845-gpi-dma";
> -        #dma-cells = <3>;
> +        #dma-cells = <2>;
>          reg = <0x00800000 0x60000>;
>          iommus = <&apps_smmu 0x0016 0x0>;
>          dma-channels = <13>;
> 
> -- 
> 2.50.1
>