[PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from aspeed or etnaviv
david at redhat.com
Thu Apr 8 22:00:48 AEST 2021
On 08.04.21 13:44, Arnd Bergmann wrote:
> On Thu, Apr 8, 2021 at 1:00 PM David Hildenbrand <david at redhat.com> wrote:
>>> It is a somewhat awkward way to say "prevent this symbol from
>>> being =y if the dependency is =m".
>> What would be the right thing to do in the case here then to achieve the
>> "if DRMA_ASPEED_GFX is enabled, also enable DMA_CMA id possible"?
>> One approach could be to have for DMA_CMA
>> default y if DRMA_ASPEED_GFX
>> but it feels like the wrong way to tackle this.
> I'm still not sure what you are trying to achieve. Is the idea only to provide
> a useful default for DMA_CMA depending on which drivers are enabled?
"Random drivers should not override a user configuration of core knobs
Let's assume I'm a distribution and want to set CONFIG_CMA=n or want to
set CONFIG_DMA_CMA=n with CONFIG_CMA=y; there is no way to do that with
e.g., DRMA_ASPEED_GFX=y because it will always override my (user!)
setting -- even though it doesn't really always need it. Using "select"
is the problem here.
> This is something you could do using a hidden helper symbol like
> config DRMA_ASPEED_GFX
> bool "Aspeed display driver"
> select DRM_WANT_CMA
> config DRM_WANT_CMA
> Select this from any driver that benefits from CMA being enabled
> config DMA_CMA
> bool "Use CMA helpers for DRM"
> default DRM_WANT_CMA
That's precisely what I had first, with an additional "WANT_CMA" -- but
looking at the number of such existing options (I was able to spot 1 !)
I wondered if there is a better approach to achieve the same; "imply"
sounded like a good candidate.
David / dhildenb
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