Date: Wed, 11 Jul 2012 23:47:50 -0400 From: Arnaud Lacombe <lacombar@gmail.com> To: Warner Losh <imp@bsdimp.com> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: newbus' ivar's limitation.. Message-ID: <CACqU3MVZmuavxcLZ8LGqP5Ze0yW4bkd5NfSFUfUK_Q6wbzDs8Q@mail.gmail.com> In-Reply-To: <CACqU3MVVDSo8fNmCcCm0dyq6skOf%2BJ_9bUWmxpBi137FD=efyg@mail.gmail.com> References: <CACqU3MVh6shncm2Vtqj9oe_HxowWscCZ1eJf0q2F%2B=t_xKKBfQ@mail.gmail.com> <31A0DCE7-3B93-41BC-805A-E0B163892112@bsdimp.com> <CACqU3MVy65ck%2Bb8TKXwfXnBV9iuFzj%2ButRBH4Ecg6XDz3Vg5kQ@mail.gmail.com> <5C18109D-E7A8-4868-BEA9-26B63360BB24@bsdimp.com> <CACqU3MUcbozpyqRLUS91p-%2BXANsisLoHzYpbQ8KjCr02=kMHYg@mail.gmail.com> <8048FFC5-6952-49FC-849D-EA1A5675ACBE@bsdimp.com> <CACqU3MVVDSo8fNmCcCm0dyq6skOf%2BJ_9bUWmxpBi137FD=efyg@mail.gmail.com>
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Hi, On Mon, Jul 9, 2012 at 1:17 AM, Arnaud Lacombe <lacombar@gmail.com> wrote: > Hi, > > On Mon, Jul 9, 2012 at 12:37 AM, Warner Losh <imp@bsdimp.com> wrote: >> >> On Jul 8, 2012, at 9:46 PM, Arnaud Lacombe wrote: >> >>> On Sun, Jul 8, 2012 at 11:31 PM, Warner Losh <imp@bsdimp.com> wrote: >>>> >>>> On Jul 8, 2012, at 9:26 PM, Arnaud Lacombe wrote: >>>> >>>>> Hi, >>>>> >>>>> On Sun, Jul 8, 2012 at 10:07 PM, Warner Losh <imp@bsdimp.com> wrote: >>>>>> >>>>>> On Jul 8, 2012, at 7:22 PM, Arnaud Lacombe wrote: >>>>>>> Ok, yet another Newbus' limitation. Assuming a device exports more >>>>>>> than one interface, and one of its child has need to use more than = one >>>>>>> interface, each interfaces cannot register, concurrently, its own >>>>>>> ivar. While I try to always have a single child per >>>>>>> interface/resource, I need to keep some compatibility with the old = way >>>>>>> of doing thing (POLA wrt. drivers I cannot/will not convert and >>>>>>> userland). So, it would have been nice if ivar had been per-interfa= ce, >>>>>>> not global and unique to one device. >>>>>> >>>>>> There's one pointer for the ivars. The bus code gets to determine w= hat the ivar looks like, because the interface is totally private to the bu= s. So long as it returns the right thing for any key that's presented, it = doesn't matter quite how things are done. >>>>>> >>>>>> So I'm not sure I understand what you are saying here. >>>>>> >>>>> dev0 implements two interfaces: A and B. dev1, child of dev0, needs t= o >>>>> use both interfaces. There is no generic way for dev0 to export >>>>> independent ivars for both interface. For now, I restricted the >>>>> function of the second interface not to need ivar, but that's kind of >>>>> hackish. >>>> >>>> Only if the IVARs for interface A and interface B have overlapping val= ues. If the Ivar keys don't overlap, then there's no problems at all. Cer= tainly less hackish than not using them at all. Since dev0 knows the layou= t of the ivar that it set on its child, this presents no problems at all. = It would return the values from A from the right part of the ivar, and thos= e from B in the right part. Apart from the coordination of Ivar numbers, a= s I outlined in my last post, there's no issue here. >>>> >>> I think we should not be talking about the same API here. I have no >>> idea what you mean by "the key to value translation", nor "Ivar >>> numbers". What I refer to is that device_set_ivars() / >>> device_get_ivars() acts on a single instance variables from `struct >>> device': `ivars'. In that case, I do not really see how to set that >>> specific field to two distinct values for each interfaces. >> >> We are talking about the ivar interface. You are just misunderstanding = how it is used. >> > yes I indeed did... silly, silly me :-) > Actually, no. I wasn't that silly, neither was I misunderstanding anything beside how *you* wanted it to be used, which is, I sorry to say, unacceptable. The last thing I want is to pollute an interface with a single-purpose, hand-crafted, bus. I was to just throw away all that ivar stuff and go into hinted child configuration for now, waiting for FDT... but of course, I figured out after a few hours that hinted child attachment requires `bus_hinted_child' to be set in the parent, as does bus_enumerate_hinted_children() / bus_generic_attach() to explicitly pollute my code. All this stuff should be done implicitly to support N:1 interfaces/client relationship. N *independent* interfaces being provided by a single driver; of course, I'm not even going back to require those interface being provided by multiple drivers, it is already a dead end. I am not even sure any driver in the tree provides more than one interface.= .. For whatever reason, I am more and more thinking that this all new-bus[0] stuff is *way* overkill, static, bloated at will, and missing critical features; a huge PITA to use, for the intended purpose. /me pissed. - Arnaud [0]: damn, why is it even called "newbus", this stuff is 14 years old. It really belongs to a museum, not production code...
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