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Date: Tue, 6 Jun 2023 16:22:01 +0200
From: Petr =?UTF-8?B?VGVzYcWZw61r?= <petr@tesarici.cz>
To: iommu@lists.linux.dev
Subject: Scatter-gather DMA
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Hi all,

while looking through the kernel code, I've noticed multiple places
which try to convert a DMA address to a struct page pointer just
because a struct page is required by the scatterlist library.

Of course, most of them do the wrong thing (e.g. amba-pl011 simply calls
phys_to_page() on the DMA address), but I wonder if this is merely a
limitation of the API. I mean, some DMA addresses are not even backed
by physical RAM, and then there is generally no struct page, but such
addresses may still be perfectly usable for scatter-gather DMA
transfers.

Is there any reason to use struct page except that the SG list API is
based on page lists?

Any comments welcome.

Petr Tesarik