Re: [PATCH v2 00/21] Allow compile-testing NO_DMA (drivers)

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Rob Herring <robherring2@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
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Subject: Re: [PATCH v2 00/21] Allow compile-testing NO_DMA (drivers)
Date: Tue, 17 Apr 2018 19:48:01 +0200	[thread overview]
Message-ID: <CAMuHMdUrLW7gdsUfKQ5FHBHh1t5ecYBSy-6ZKxPSJoP6TQzXvw@mail.gmail.com> (raw)
In-Reply-To: <CAL_JsqJMppYaz31Gg8BH2OaAxs56dnjZ4y+nzBBp-Tt2odaqCw@mail.gmail.com>

Hi Rob,

On Thu, Apr 5, 2018 at 2:32 AM, Rob Herring <robherring2@gmail.com> wrote:
> On Fri, Mar 16, 2018 at 8:51 AM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> 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.

Perhaps, if time permits...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds