Date: Sat, 21 Jan 2012 13:02:59 +0100 From: Stefan Bethke <stb@lassitu.de> To: Warner Losh <imp@bsdimp.com> Cc: FreeBSD-arch <freebsd-arch@FreeBSD.org> Subject: Re: Extending sys/dev/mii Message-ID: <0759FAC9-D4CD-444D-A7A4-545383709631@lassitu.de> In-Reply-To: <8EF24110-C985-400F-ADDF-B1D63C4E304B@bsdimp.com> References: <8D025847-4BE4-4B2C-87D7-97E72CC9D325@lassitu.de> <20120104215930.GM90831@alchemy.franken.de> <47ABA638-7E08-4350-A03C-3D4A23BF2D7E@lassitu.de> <1763C3FF-1EA0-4DC0-891D-63816EBF4A04@lassitu.de> <20120106182756.GA88161@alchemy.franken.de> <95372FB3-406F-46C2-8684-4FDB672D9FCF@lassitu.de> <20120106214741.GB88161@alchemy.franken.de> <F60B2B70-049F-4497-BBA8-3C421088C1EA@lassitu.de> <20120108130039.GG88161@alchemy.franken.de> <23477898-8D85-498C-8E30-192810BD68A8@lassitu.de> <20120111193738.GB44286@alchemy.franken.de> <66DDA0A2-F878-43FF-8824-54868F493B18@lassitu.de> <8EF24110-C985-400F-ADDF-B1D63C4E304B@bsdimp.com>
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Am 21.01.2012 um 02:43 schrieb Warner Losh: >=20 > On Jan 20, 2012, at 5:08 PM, Stefan Bethke wrote: >> The second problem is that there's currently no way to express a = dependency between two devices other than a parent-child relationship. = I would be interested to learn why this appears to be so uncommon that I = could not find any discussion of such a feature. Has it really never = before come up? >=20 > Sure there is: you can do it by name. I wrote a driver that attached = to the ISA bus, but also needed to talk to the ppbus that was attached = to the printer. My solution was to have a post-attach name-lookup so = that it could then call methods on the other driver's device_t. I = wonder why we can't do that here? That was my first approach, but the attachment sequence foiled it: arge0 = is probed and attached before the device that provides the MDIO bus = arge0 needs to attach the miibus and phy. As far as I can tell, there = is no way to express (via code or hints or otherwise) that a device = should be attached only after some other device has been attached. The solution for me was to write miiproxy which contains code that waits = for both devices to attach, and then calls a callback on arge0 to = complete the interface attachment (attaches miibus, makes the interface = available). =46rom a driver writers point of view, it would be desirable to be able = to say "attach this only after 'foo0' has been attached", so the attach = method can still be a single, linear piece of code. Stefan --=20 Stefan Bethke <stb@lassitu.de> Fon +49 151 14070811
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