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

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Message-ID: <5085c857-f6e8-4faf-b61a-a9ee562ccf06@kernel.org>
Date: Thu, 9 Oct 2025 10:04:24 +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 09:55, Bryan O'Donoghue wrote:
> On 09/10/2025 01:47, Krzysztof Kozlowski wrote:
>>> 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.
> 
> But at least as I understand it, you can have multiple SID entries that 
> need to map to a FUNCTION_ID which means you need to encode that 
> inferred indexing in your driver.

Yes.

> 
> So you can't have the iommu code just know what to do.. it has to be 
> driver specific.

Yes.

> 
> The iommu description for this platform basically lacks the data that 
> _should_ be there -> FUNCTION_ID.

No. The index tells that already.

> 
> The rule is that the DT should really describe the hardware right ?

It already does. Same as I wrote on IRC, DT already has all the
information. Entry 0 has function ID-foo. Entry 1 has function ID-bar.
Entry 2 has function ID-bar or whatever.

Best regards,
Krzysztof