Date: Fri, 12 Sep 2003 14:26:30 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Doug Rabson <dfr@nlsystems.com> Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: When to burn those bridges Message-ID: <XFMail.20030912142630.jhb@FreeBSD.org> In-Reply-To: <1063353880.5536.6.camel@herring.nlsystems.com>
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On 12-Sep-2003 Doug Rabson wrote: > 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. Yes, I wish we had better drivers so we didn't have to do that, but that might be the best for now. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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