Re: [PATCH 05/39] drm/imx: dc: Rework dc_subdev_get_id() to drop ARRAY_SIZE() use

[Liu Ying <victor.liu@nxp.com>]

On 10/15/2025, Frank Li wrote:
> On Wed, Oct 15, 2025 at 05:14:02PM +0800, Liu Ying wrote:
>> On 10/14/2025, Marek Vasut wrote:
>>> On 10/14/25 5:11 PM, Frank Li wrote:
>>>> On Tue, Oct 14, 2025 at 04:03:37PM +0200, Marek Vasut wrote:
>>>>> On 10/13/25 6:56 PM, Frank Li wrote:
>>>>>> On Sat, Oct 11, 2025 at 06:51:20PM +0200, Marek Vasut wrote:
>>>>>>> Rework dc_subdev_get_id() to drop ARRAY_SIZE() use and use empty trailing
>>>>>>> entry in each ID look up array instead. This allows passing of those arrays
>>>>>>> around as OF match data, which will be useful when using this pipeline on
>>>>>>> i.MX95, which has different address-to-ID mapping.
>>>>>>>
>>>>>>> Signed-off-by: Marek Vasut <marek.vasut@mailbox.org>
>>>>>>
>>>>>> This change is okay. but my questions is why need map register to id.
>>>>>
>>>>> This seems to be a recurring pattern in the driver, where some components
>>>>> need to find other components to link with them. The mapping is fixed, and
>>>>> since the DT does not encode link IDs, the resolution of the mapping has to
>>>>> happen by mapping the component base addresses to the IDs first.
>>>>
>>>> In graphic link, port@<n>, n should be id? why not use it?
>>> I suspect you could model the relationships between the DC blocks using OF
>>> graph, yes. I also suspect that description would be very complex in
>>> DT, considering the amount of blocks and links this device contains. I
>>> suspect this is why there is no such DT description using OF graph.
>>
>> Yes.  The design decision was made to avoid using OF graph to describe
>> links between DC blocks due to the complexity.
> 
> Any previous discuission? Using registers base address to determiate ID

Yes, you may find the discussion in
https://patchwork.freedesktop.org/series/135786/

> is not solution.

Well it is, based on the discussion.  And it's also used by MSM DPU,
see drivers/gpu/drm/msm/disp/dpu1/catalog/*.h, though IIRC someone said
it's not the best solution for MSM DPU.

> 
> Frank
> 
>>
>>>
>>> I think it might also be good to talk to Liu directly about the original design
>>> decision and why this id mapping was done the way it was done,
>>> they should know better than me.
>>
>>
>> --
>> Regards,
>> Liu Ying


-- 
Regards,
Liu Ying