Date: 12 Sep 2003 09:04:40 +0100 From: Doug Rabson <dfr@nlsystems.com> To: "M. Warner Losh" <imp@bsdimp.com> Cc: arch@freebsd.org Subject: Re: When to burn those bridges Message-ID: <1063353880.5536.6.camel@herring.nlsystems.com> In-Reply-To: <20030912.013911.13774129.imp@bsdimp.com> References: <20030911.153929.44983352.imp@bsdimp.com> <XFMail.20030912013027.jhb@FreeBSD.org> <20030912.013911.13774129.imp@bsdimp.com>
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On Fri, 2003-09-12 at 08:39, M. Warner Losh wrote: > In message: <XFMail.20030912013027.jhb@FreeBSD.org> > John Baldwin <jhb@freebsd.org> writes: > : How do you know which drivers to detach? Are you going to detach > : the generic PCI ATA driver on every kldload? Are you going to > : detach the generic PCI-PCI bridge driver for PCI-PCI bridges on > : add-on cards for every kldload of a PCI driver? That would be > : freaking insane. The problem is that you don't know what devices > : a new driver might be more suitable for than existing drivers. > > This does suck. > > : > 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.... > : > : rl(4) and re(4)? Several drivers still allocate resources in probe(), > : which would break things. > > yea, but that's a bit of a pathological case. first, rl/re attach to > a specific driver, and not override. So maybe we could mandate that > drivers that are generic and return negative return values should be > constrained to only look at the plug and play info and are not allowed > to look at resources. owi/wi is the only pair that does this > evilness. This is why I was thinking about a device flag which a driver would set if it is just a placeholder which can be pre-empted safely.
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