On Tue, 27 Mar 2018 16:45:02 +0200 Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> wrote: > On 27/03/2018 13:17, Cornelia Huck wrote: > > On Thu, 15 Mar 2018 13:25:25 -0400 > > Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote: > > > >> On 03/15/2018 09:25 AM, Pierre Morel wrote: > >>> On 14/03/2018 19:25, Tony Krowiak wrote: > >>>> +config VFIO_AP > >>>> + def_tristate m > >>> not sure it must be module by default. > >>> I would not set it by default. > >> Connie also asked about this in the last review, so I will go ahead > >> and change it. > >>> > >>>> + prompt "VFIO support for AP devices" > >>>> + depends on ZCRYPT && VFIO_MDEV_DEVICE > >>> VFIO_MDEV_DEVICE is a general feature *needed* by VFIO_AP > >>> and has no use case by its own. If it is set it is obviously because some > >>> mediated device drivers needs it. > >>> while ZCRYPT is a Z feature which may be set without VFIO_AP. > >>> > >>> So you need: > >>> > >>> config VFIO_AP > >>> def_tristate n > >>> prompt "VFIO support for AP devices" > >>> depends on ZCRYPT > >>> select VFIO_MDEV > >>> select VFIO_MDEV_DEVICE > >>> ... > >> I was thinking the same just yesterday and I agree, this makes sense. > > OTOH, nobody else seems to do a select on these symbols so far. > > > > If you decide to go that route, you'll also need to depend on VFIO > > I think a select is better (again). > > > (otherwise you could end up selecting symbols with unmet dependencies). > > All in all, I prefer the 'depends' approach. > > > Why do you prefer this approach? Hm, I thought I had already written a mail, but apparently I didn't.... > I can tell you why I prefer a mixed approach: > > We have two tools, depends and select. > > It seems to me that depends should be used for things we can not choose > to be there or not, but things that just are there, like hardware > dependencies. For example MMU, CPU type, CRYPTO hardware... > > Select on the other hand is useful to choose things that we need like > libraries, VFIO, VIRTIO, crypto libraries etc. > > Using this policy is clear and makes easy to choose functionalities and > get the utilities automatically. > > On the other hand, only using depends makes things to hide the > functionalities behind the utilities. My view is the following: - select is useful for library functionality or for enabling architecture-specific optimizations (the HAVE_xxx symbols), especially things you don't want the user to deal with. If you select something, you need to take care of any dependencies yourself. - depends is useful for more complex dependencies, and especially things you don't want automagically enabled. [In modern menuconfig, it is easy to figure out any missing dependencies for a config option anyway.] The mdev infrastructure is too complex to be considered a simple library IMO (cf. the missing VFIO dependency).
