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

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Message-ID: <zoe23ugsqyqqz5edpxa6nsppqocwrxq56ekpd76r4ptnz2p5aq@iwnrpjuu47pk>
Date: Wed, 8 Oct 2025 06:13:58 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Bryan O'Donoghue <bod@...nel.org>
Cc: Bryan O'Donoghue <bod.linux@...w.ie>,
        Charan Teja Kalla <charan.kalla@....qualcomm.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        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 Wed, Oct 08, 2025 at 06:10:26AM +0300, Dmitry Baryshkov wrote:
> On Tue, Oct 07, 2025 at 11:10:28PM +0100, Bryan O'Donoghue wrote:
> > On 07/10/2025 20:40, Dmitry Baryshkov wrote:
> > > > Surely we could do
> > > > 
> > > >       #iommu-cells = <4>;
> > > Because #iommu-cells is a part of the apps_smmu: device rather than a
> > > part ofthe iris/venus/GPU/display/etc.
> > 
> > What's to stop us extending the definition for qcom platforms ?
> > 
> > Rather than jumping through hoops in drivers, we can just encode the data in
> > the DT.
> 
> The IOMMU driver or a ARM SMMU device itself has nothing to do with the
> way individual devices use it. As such, I don't think we should be
> extending #iommu-cells in the SMMU device.

... and I don't think that we should be encoding IOMMUs or other
definitions inside the driver, if we can express them clearly in DT.

-- 
With best wishes
Dmitry