In practical terms, it will be easier to keep the freezer where it is
for now. This is because prepare() requires drivers to change their
behavior; they aren't allowed to register new children any more.
But if userspace isn't frozen then user programs can interact with
drivers in a way that does cause new children to be created. For
example this happens in USB, where opening an audio device and
selecting its bitrate causes a new set of endpoints to be realized,
along with their representations in sysfs.
Thus, in addition to making all the interface changes implied by the
new callbacks, drivers would also have to change the way they interact
with userspace. Yes, this will have to be done eventually in any case,
as the freezer goes away -- but it shouldn't have to be done right now.
Alan Stern
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