linux-kernel - Re: [PATCH 2/7] OF: Simplify DMA range calculations

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Message-ID: <20231130004603.GB1394392@ziepe.ca>
Date:   Wed, 29 Nov 2023 20:46:03 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Joerg Roedel <joro@...tes.org>, Christoph Hellwig <hch@....de>,
        Vineet Gupta <vgupta@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-acpi@...r.kernel.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/7] OF: Simplify DMA range calculations

On Wed, Nov 29, 2023 at 05:42:59PM +0000, Robin Murphy wrote:
> Juggling start, end, and size values for a range is somewhat redundant
> and a little hard to follow. Consolidate down to just using inclusive
> start and end, which saves us worrying about size overflows for full
> 64-bit ranges (note that passing a potentially-overflowed value through
> to arch_setup_dma_ops() is benign for all current implementations, and
> this is working towards removing that anyway).

In iommu code I've been trying to use consistent language with other
parts of the kernel like interval tree and maple tree:

 * In this file the term 'last' indicates an inclusive and closed interval, eg
 * [0,0] refers to a single PFN. 'end' means an open range, eg [0,0) refers to
 * no PFNs.

Here I think you've swapped end to mean last?

Regardless the change looks correct

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason