Re: [PATCH RFC v4 1/4] media: dt-bindings: Add Amlogic V4L2 video decoder

[Krzysztof Kozlowski]

On 13/02/2026 09:31, Zhentao Guo wrote:
>>>>> +  power-domains:
>>>>> +    maxItems: 2
>>>>> +
>>>>> +  power-domain-names:
>>>>> +    items:
>>>>> +      - const: vdec
>>>>> +      - const: hevc
>>>>> +
>>>>> +  resets:
>>>>> +    maxItems: 1
>>>>> +
>>>>> +  amlogic,canvas:
>>>>> +    description: should point to a canvas provider node
>>>> Why? What for?
>>>>
>>>> What is canvas provider?
>>> The canvas provider is: drivers/soc/amlogic/meson-canvas.c
>> What is this "canvas" device.
> You can think of canvas as the agent through which the decoder hardware 
> accesses DDR.

AGAIN:

What is the canvas device. Describe or point me to bindings describing
it. Your current bindings say that canvas is "a collection of metadata
that describes a pixel buffer" so there is no way it handles DDR access.

NAK

>>> In short, canvas is a hardware IP inside the Amlogic SoC. The decoder IP
>>> needs to access DDR through canvas IP, so we need to reference the
>> Why decoder cannot access DDR directly?
> The internal topology of the S4 chip is designed this way, we don't know 
> why our VLSI colleauges designed like this. But similar designs have 
> been removed in subsequent chips, eliminating the need to rely on a 
> common hardware IP.

Quite poor explanation. Based on this, this as well could be entry in
device reg lists.

Anyway, I am done guessing, explain properly the hardware instead of
answering with half-baked responses just so I will go away.


Best regards,
Krzysztof