When to burn those bridges

[M. Warner Losh]

In message: <XFMail.20030911105053.jhb at FreeBSD.org>
            John Baldwin <jhb at freebsd.org> writes:
: I have thought about this as well, but instead of a placeholder flag,
: just doing this for any driver that returned a probe value != 0.
: This relies on very simple probes however, since ideally you would
: want to execute the new driver's probe and if it matches better, then
: you detach the old driver and attach the new one.   This requires
: that the new driver's probe not try to alloc resources or dink with
: the hardware though.

I've thought seriously about just detatching the older driver, if
possible.  If that succeeds, we reprobe.  This has the advantage of
being easy to implement, but does cause a fair amount of churn.

Besides, proble routines on self enumerating devices should look at
the IDs that anybody can look at at any time.  However, there are some
issues with some drivers that have old/new versions or that need to
ask the hardware what kind of thing it really is before making the
call.  These drivers are rare, thankfully, and even rarer are those
that have different levels.  owi/wi is the only one I know of that
fits this bill, and the only reason owi is there is to help fix wi, so
I don't think we should necessarily design to make this sort of thing
too easy....

Warner