linux-kernel - Re: [PATCH] media: dt-bindings: qcom,sm8550-iris: Do not reference legacy venus properties

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Message-ID: <20250825113734.iekrgyvctamhb5y7@hu-mojha-hyd.qualcomm.com>
Date: Mon, 25 Aug 2025 17:07:34 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: dt-bindings: qcom,sm8550-iris: Do not reference
 legacy venus properties

On Sat, Aug 23, 2025 at 05:53:50PM +0200, Krzysztof Kozlowski wrote:
> The Qualcomm SoC Iris video codec is an evolution of previous Venus and
> it comes with its own Iris Linux drivers.  These new drivers were
> accepted under condition they actually improve state of afairs, instead
> of duplicating old, legacy solutions.
> 
> Unfortunately binding still references common parts of Venus without
> actual need and benefit.  For example Iris does not use fake
> "video-firmware" device node (fake because there is no actual device
> underlying it and it was added only to work around some Linux issues
> with IOMMU mappings).
> 
> Stop referencing venus-common schema in the new Qualcomm Iris bindings
> and move all necessary properties, except unused "video-firmware" (no
> driver usage, no DTS).
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>  .../devicetree/bindings/media/qcom,sm8550-iris.yaml | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> index c79bf2101812..320227f437a1 100644
> --- a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> +++ b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> @@ -26,6 +26,9 @@ properties:
>            - qcom,sm8550-iris
>            - qcom,sm8650-iris
>  
> +  reg:
> +    maxItems: 1
> +
>    power-domains:
>      maxItems: 4
>  
> @@ -45,6 +48,12 @@ properties:
>        - const: core
>        - const: vcodec0_core
>  
> +  firmware-name:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
>    interconnects:
>      maxItems: 2
>  
> @@ -69,6 +78,9 @@ properties:
>  
>    dma-coherent: true
>  
> +  memory-region:
> +    maxItems: 1
> +
>    operating-points-v2: true
>  
>    opp-table:
> @@ -85,7 +97,6 @@ required:
>    - dma-coherent
>  
>  allOf:
> -  - $ref: qcom,venus-common.yaml#
>    - if:

Saw your reply on 
https://lore.kernel.org/lkml/59951c47-1015-4598-a885-25f8f1a27c64@kernel.org/

Just trying to understand ABI here, how all of a sudden we remove a binding
for a hardware just because it did not get noticed until yet that as it is
not a real device and we always say device tree binding should not depend on
drivers but the device but we are saying Iris does not use fake "video-firmware"
device node for removal. I am a bit confused.

Whether removing will not break any ABI as initial binding enables the IRIS
related code to use video-firmware, now we are removing it.
I believe, removing binding always break ABI ? or is it depend on driver
code not using it ?


>        properties:
>          compatible:
> -- 
> 2.48.1
> 

-- 
-Mukesh Ojha