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Fri, 17 Jul 2026 09:07:17 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wkl5o-00000004hEV-4513; Fri, 17 Jul 2026 13:07:16 -0300 Date: Fri, 17 Jul 2026 13:07:16 -0300 From: Jason Gunthorpe To: Konrad Dybcio Cc: Krzysztof Kozlowski , Vishnu Reddy , Rob Herring , Krzysztof Kozlowski , Conor Dooley , devicetree@vger.kernel.org, Vikash Garodia , Robin Murphy , joro@8bytes.org, will@kernel.org, m.szyprowski@samsung.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, dikshita.agarwal@oss.qualcomm.com, Bjorn Andersson , Dmitry Baryshkov , Robin Clark , Akhil P Oommen , Srinivas Kandagatla , Ekansh Gupta , Loic Poulain Subject: Re: [PATCH] dma-iommu: Introduce API to reserve IOVA regions for dynamically created devices Message-ID: <20260717160716.GA701389@ziepe.ca> References: <20260612172649.GM1066031@ziepe.ca> <20260615125257.GS1066031@ziepe.ca> <20260617194038.GC231643@ziepe.ca> <20260618151745.GD231643@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jul 17, 2026 at 12:44:54PM +0200, Konrad Dybcio wrote: > I was kinda hoping there would be more buy-in to follow what PCIe > does, but to my understanding you're opposed to it because "vpu_bus" > is not dynamically discoverable. PCIe allows describing devices in DT. What this weird vpu_bus thing seems to be about is to actively avoid describing the devices in DT while simultaenously treating them like devices. I think it makes no sense.. IMHO the approach inverts the thing, you start the main driver then use vpu_bus to dynamically create a bunch of struct device DMA handles for the main driver to use. I think it is much better if you start the main driver, use the new component stuff: https://docs.kernel.org/driver-api/component.html To aggregate a driver from the struct device DMA handles that DT will create automatically. ie the reversed flow, the struct devices pre-exist created by DT instead of being created by code in your driver. Jason