Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 8 Apr 2021 12:20:50 +0200 | Subject | Re: [PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from aspeed or etnaviv |
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On Thu, Apr 8, 2021 at 11:22 AM David Hildenbrand <david@redhat.com> wrote: > > Random drivers should not override a user configuration of core knobs > (e.g., CONFIG_DMA_CMA=n). Use "imply" instead, to still respect > dependencies and manual overrides. > > "This is similar to "select" as it enforces a lower limit on another > symbol except that the "implied" symbol's value may still be set to n > from a direct dependency or with a visible prompt." > > Implying DRM_CMA should be sufficient, as that depends on CMA. > > Note: If this is a real dependency, we should use "depends on DMA_CMA" > instead - but I assume the driver can work without CMA just fine -- > esp. when we wouldn't have HAVE_DMA_CONTIGUOUS right now.
'imply' is almost never the right solution, and it tends to cause more problems than it solves.
In particular, it does not prevent a configuration with 'DRM_CMA=m' and 'DRMA_ASPEED_GFX=y', or any build failures from such a configuration.
If you want this kind of soft dependency, you need 'depends on DRM_CMA || !DRM_CMA'.
Arnd
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