DRM Format Modifiers in v4l2

[Nicolas Dufresne]

Le jeudi 31 août 2017 à 17:28 +0300, Laurent Pinchart a écrit :
> > e.g. if I have two devices which support MODIFIER_FOO, I could attempt
> > to share a buffer between them which uses MODIFIER_FOO without
> > necessarily knowing exactly what it is/does.
> 
> Userspace could certainly set modifiers blindly, but the point of modifiers is 
> to generate side effects benefitial to the use case at hand (for instance by 
> optimizing the memory access pattern). To use them meaningfully userspace 
> would need to have at least an idea of the side effects they generate.

Generic userspace will basically pick some random combination. To allow
generically picking the optimal configuration we could indeed rely on
the application knowledge, but we could also enhance the spec so that
the order in the enumeration becomes meaningful.

regards,
Nicolas
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