Re: nasty device_delete_child interaction

[John Wehle <john@xxxxxxxxx>]

> Don't do that.  You are duplicating the storage of children in two
> places.  If you need to cache a copy of a child, that's fine.
> However, don't delete it explicitly in xxx_detach.
> 
> I'd say that these drivers are wrong and should be fixed.

What's the correct approach?

Currently (at least in FreeBSD 4.9) if_xl.c uses device_add_child
in the attach routine to add on miibus.  It then calls device_delete_child
in the detach routine to delete miibus (creating a nice symmetry).

Should if_xl.c still call device_add_child in the attach and simply
not call device_delete_child?  Then who's responsible for deleting
miibus when if_xl is unloaded?

>: > It seems to me that any driver which calls device_delete_child
>: > as part of detaching must also implement something like:
>
> No.  They should avoid the problem by using newbus correctly.  This
> sort of solution just adds code to no good purpose.

If the driver has cached a copy of a child, then doesn't
xxx_child_detached still need to be implemented so the driver
knows when the cached copy is invalid?

-- John
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