Date: Sun, 29 Jan 2012 00:05:50 -0700 From: Warner Losh <imp@bsdimp.com> To: Juli Mallett <jmallett@FreeBSD.org> Cc: Aleksandr Rybalko <ray@ddteam.net>, Stefan Bethke <stb@lassitu.de>, freebsd-net@FreeBSD.org, Adrian Chadd <adrian@FreeBSD.org>, Aleksandr Rybalko <ray@FreeBSD.org>, freebsd-arch@FreeBSD.org Subject: Re: Ethernet Switch Framework Message-ID: <DBAB0C5C-5B2D-4430-8096-9E4DC7233961@bsdimp.com> In-Reply-To: <CACVs6=-U9rr7cpeJ%2BVUgP3Xq1yRB=Xk1GjuzEOuXiEUoqGFq_Q@mail.gmail.com> References: <20120120221319.ca8b631f.ray@freebsd.org> <30A45A1E-CA13-4AC8-86FB-F8E06301D1F6@lassitu.de> <20120122195130.360261ce.ray@freebsd.org> <CAJ-VmokTh2q0ZH=kwU6GzJm5Mr4k7geJiFsoX_A9hcLhMZNxsg@mail.gmail.com> <0E31FEC4-963D-4AC8-9AB7-EE6D6D7F86EE@lassitu.de> <CAJ-Vmo=GRKRf%2BYsFqNm9d_T3Tq583uV_pabMV6ozuaytSRLivg@mail.gmail.com> <20120129001251.7e4cfe83.ray@ddteam.net> <CACVs6=-U9rr7cpeJ%2BVUgP3Xq1yRB=Xk1GjuzEOuXiEUoqGFq_Q@mail.gmail.com>
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On Jan 28, 2012, at 4:00 PM, Juli Mallett wrote: > It makes me wonder if the understanding of the relationship in FreeBSD > isn't backwards. Yes, the MAC sits on a bus and is memory-mapped, but > you can conceptualize of it as a child of the PHY, rather than the > parent of it, especially in systems with switch chipsets. Especially > in systems where there is a switch chipset attached to multiple MACs. >=20 > In that model, it makes sense to semi-generically attach a > CPU-to-switch port's pseudo-PHY (or actual PHY, depending on hardware) > to a MAC generically, but that doesn't meant that the switch itself is > attached generically to the MAC. I think that the main issue here is that we have an assumption that we = have a tree structure. However, it is more of a DAG across different = domains. The hierarchy works well when each device owns all the devices = below it and only interacted with them. Most devices are that way. = However, in the embedded world, there's lots of reach-accrosses that are = expected that break the model. Plus, MDIO is more than what we call mii/phy, so there's an imperfect = match there. Warner
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