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Date:   Mon, 21 Mar 2022 17:17:14 +0000
From:   Alyssa Rosenzweig <alyssa@rosenzweig.io>
To:     Sven Peter <sven@svenpeter.dev>
Cc:     Hector Martin <marcan@marcan.st>, Rob Herring <robh+dt@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Keith Busch <kbusch@kernel.org>,
        Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Marc Zyngier <maz@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-nvme@lists.infradead.org
Subject: Re: [PATCH 4/9] soc: apple: Add SART driver
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References: <20220321165049.35985-1-sven@svenpeter.dev>
 <20220321165049.35985-5-sven@svenpeter.dev>
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> +/*
> + * Adds the region [paddr, paddr+size] to the DMA allow list.
> + *
> + * @sart: SART reference
> + * @paddr: Start address of the region to be used for DMA
> + * @size: Size of the region to be used for DMA.
> + */
> +int apple_sart_add_allowed_region(struct apple_sart *sart, phys_addr_t paddr,
> +				  size_t size);
> +
> +/*
> + * Removes the region [paddr, paddr+size] from the DMA allow list.
> + *
> + * Note that exact same paddr and size used for apple_sart_add_allowed_region
> + * have to be passed.
> + *
> + * @sart: SART reference
> + * @paddr: Start address of the region no longer used for DMA
> + * @size: Size of the region no longer used for DMA.
> + */
> +int apple_sart_remove_allowed_region(struct apple_sart *sart, phys_addr_t paddr,
> +				     size_t size);

Might it be simpler for add_allowed_region to return a handle that
remove_allowed_region takes instead of paddr+size? Then
remove_allowed_region doesn't have to walk anything, and the requirement
to use the same paddr/size is implicit.