Re: [RFC PATCH 1/5] hw/mem/nvdimm: Use Kconfig 'imply' instead of 'depends on'

[Paolo Bonzini]

On 12/05/21 09:02, David Gibson wrote:
> > But with "imply" you could end up with a PSERIES that does not have NVDIMM
> > when also using --without-default-devices, couldn't you? Why don't you use
> > "select" instead of "imply" ?
> Oh.. clearly I misunderstand the semantics of "imply".  If we don't
> need NVDIMM for PSERIES, why does there need to be any Kconfig
> connection between them at all?

Because you still want it in the binary by default (i.e. unless 
--without-default-devices).

Basically,

config PSERIES
    imply NVDIMM

is the same as

config NVDIMM
    default y if PSERIES

Both of them are a way to say "PSERIES can work with NVDIMM so you want 
to include it unless you want some fine tuning".  In Linux "imply" is 
very rarely used, while in QEMU it's quite common because it keeps the 
many per-board defaults close together.

Paolo