On 08.04.21 13:44, Arnd Bergmann wrote:
On Thu, Apr 8, 2021 at 1:00 PM David Hildenbrand <david@xxxxxxxxxx> 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
(e.g., CONFIG_DMA_CMA=n)."
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
bool
help
Select this from any driver that benefits from CMA being enabled
config DMA_CMA
bool "Use CMA helpers for DRM"
default DRM_WANT_CMA
Arnd
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.
--
Thanks,
David / dhildenb
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