On Fri, Apr 9, 2021 at 1:20 PM David Hildenbrand david@redhat.com wrote:
Random drivers should not override a user configuration of core knobs (e.g., CONFIG_DMA_CMA=n). Applicable drivers would like to use DMA_CMA, which depends on CMA, if possible; however, these drivers also have to tolerate if DMA_CMA is not available/functioning, for example, if no CMA area for DMA_CMA use has been setup via "cma=X". In the worst case, the driver cannot do it's job properly in some configurations.
Looks good to me. At least a lot better than what we have. Reviewed-by: Linus Walleij linus.walleij@linaro.org
Let's see if this approach is better for soft dependencies (and if we actually have some hard dependencies in there). This is the follow-up of https://lkml.kernel.org/r/20210408092011.52763-1-david@redhat.com https://lkml.kernel.org/r/20210408100523.63356-1-david@redhat.com
You can just add these to the commit message with Link: when applying so people can easily find the discussion from the commit.
I was wondering if it would make sense in some drivers to warn if either CONFIG_DMA_CMA is not available or if DRM_CMA has not been configured properly - just to give people a heads up that something might more likely go wrong; that would, however, be future work.
I think the frameworks (DRM_*_CMA_HELPER) should pr_info something about it so the individual drivers don't have to sanity check their entire world.
Yours, Linus Walleij