linux-kernel - Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video node

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Message-ID: <a0dc93ec-e35c-409b-8dfb-1642c92a9f0c@kernel.org>
Date: Thu, 9 Oct 2025 09:47:01 +0900
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Bryan O'Donoghue <bod@...nel.org>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Charan Teja Kalla <charan.kalla@....qualcomm.com>,
 Bryan O'Donoghue <bod.linux@...w.ie>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Vikash Garodia <quic_vgarodia@...cinc.com>,
 Dikshita Agarwal <quic_dikshita@...cinc.com>,
 Abhinav Kumar <abhinav.kumar@...ux.dev>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video
 node

On 09/10/2025 09:43, Bryan O'Donoghue wrote:
> On 09/10/2025 01:32, Krzysztof Kozlowski wrote:
>>>> Since it is the smmu device property , this suggestion expects all the
>>>> devices, not just video, to define additional argument. Does this look
>>>> valid?
>>> If it is legitimate meta-data for the SMMU setup then why_shouldn't_ it
>>> go into the DT ?
>>>
>> We talked about this two or three months ago. I don't understand why you
>> just ignored that entire part and come with new binding just to not
>> touch iommu code. List of entries in iommu must have strict order, just
>> like for every other list, and you should rely on that.
> 
> I don't know if you mean me here.

I meant Qualcomm. Anyway this was already proposed and received the same
feedback from Rob, so you are a bit duplicating the discussion here.

> 
> Just to clarify my point is; the FUNCTION_ID is just as legitimate as 
> the SID to specify in the DT.
> 
> It shouldn't be in driver platform data. It perfectly valid to add 
> another field to the iommu and then modify the iommu code to parse that 
> additional field we have added.
> 
> There has been some suggestion of an inferred index, I'm not sure how 
> that could really work.
> 
> The right thing to do is:
> 
> - Add FUNCTION_ID to the iommu entries
> - Modify the iommu code to consume that data.
> 
> Maybe it would be possible to also use an inferred FUNCTION_ID somehow 
> though TBH I think that's a work-around.

Three months ago I gave you the answer for that - it is inferred by
index on the list.


Best regards,
Krzysztof