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