On 08.04.21 12:27, David Hildenbrand wrote:
On 08.04.21 12:20, Arnd Bergmann wrote:
On Thu, Apr 8, 2021 at 11:22 AM David Hildenbrand <david@xxxxxxxxxx> 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.
I thought that was the case with "select" :)
In particular, it does not prevent a configuration with 'DRM_CMA=m'
I assume you meant "DRM_CMA=n" ? DRM_CMA cannot be built as a module.
and 'DRMA_ASPEED_GFX=y', or any build failures from such
a configuration.
I don't follow. "DRM_CMA=n" and 'DRMA_ASPEED_GFX=y' is supposed to work
just fine (e.g., without HAVE_DMA_CONTIGUOUS) or what am I missing?
If you want this kind of soft dependency, you need
'depends on DRM_CMA || !DRM_CMA'.
Seriously? I think the point of imply is "please enable if possible and
not prevented by someone else". Your example looks more like a NOP - no?
Or will it have the same effect?
I just tried (remove CONFIG_DMA_CMA from .config followed by make) and
the default will be set to "N" (when querying the user). So it indeed
looks like a NOP - unless I am missing something.
--
Thanks,
David / dhildenb
