From: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v2 00/21] Allow compile-testing NO_DMA (drivers)
Date: Wed, 4 Apr 2018 19:32:53 -0500
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Cc: Ulf Hansson <ulf.hansson-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>,
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To: Geert Uytterhoeven <geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org>
In-Reply-To: <1521208314-4783-1-git-send-email-geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org>
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On Fri, Mar 16, 2018 at 8:51 AM, Geert Uytterhoeven
<geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org> wrote:
>         Hi all,
>
> If NO_DMA=y, get_dma_ops() returns a reference to the non-existing
> symbol bad_dma_ops, thus causing a link failure if it is ever used.
>
> The intention of this is twofold:
>   1. To catch users of the DMA API on systems that do no support the DMA
>      mapping API,
>   2. To avoid building drivers that cannot work on such systems anyway.
>
> However, the disadvantage is that we have to keep on adding dependencies
> on HAS_DMA all over the place.
>
> Thanks to the COMPILE_TEST symbol, lots of drivers now depend on one or
> more platform dependencies (that imply HAS_DMA) || COMPILE_TEST, thus
> already covering intention #2.  Having to add an explicit dependency on
> HAS_DMA here is cumbersome, and hinders compile-testing.

The same can be said for CONFIG_IOMEM and CONFIG_OF. Any plans to
remove those too? CONFIG_IOMEM is mostly just a !CONFIG_UM option.

Rob