Date: Thu, 29 Jan 2004 14:59:02 -0500 (EST) From: John Wehle <john@feith.com> To: imp@bsdimp.com Cc: jhb@FreeBSD.org Subject: Re: nasty device_delete_child interaction Message-ID: <200401291959.i0TJx2m25103@jwlab.FEITH.COM>
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> 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 ------------------------------------------------------------------------- | Feith Systems | Voice: 1-215-646-8000 | Email: john@feith.com | | John Wehle | Fax: 1-215-540-5495 | | -------------------------------------------------------------------------
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