Date: Tue, 21 Feb 2012 11:08:21 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Juli Mallett <jmallett@freebsd.org> Cc: Marcel Moolenaar <marcel@xcllnt.net>, Adrian Chadd <adrian@freebsd.org>, Brooks Davis <brooks@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it>, net@freebsd.org Subject: Re: Abstracting struct ifnet Message-ID: <20120221090821.GE55074@deviant.kiev.zoral.com.ua> In-Reply-To: <CACVs6=9efUMQHTr9RH9SHm=Apo0PV7NeKcwFyV%2B2k9HCFNjS9g@mail.gmail.com> References: <338757D1-6B1E-49CF-983F-5D5851066FD3@xcllnt.net> <20120220231601.GA51310@lor.one-eyed-alien.net> <20120221001552.GA60050@onelab2.iet.unipi.it> <CAJ-Vmoni1DHpxet08=JWSDGLFBP7MHO4-WDBLwX9vGxibR=EDA@mail.gmail.com> <CACVs6=_kTVC7tnsPJqgRq3VtUaSefkunVU8JetTdsXjGCmUT7A@mail.gmail.com> <CAJ-Vmo=T28t0XBmzmkNjOEA6wJ-Ub3Bc9DiWu1upDpBt8bM=XA@mail.gmail.com> <CACVs6=9efUMQHTr9RH9SHm=Apo0PV7NeKcwFyV%2B2k9HCFNjS9g@mail.gmail.com>
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--4Epv4kl9IRBfg3rk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 20, 2012 at 06:42:15PM -0800, Juli Mallett wrote: > On Mon, Feb 20, 2012 at 18:34, Adrian Chadd <adrian@freebsd.org> wrote: > > Is the target though _binary_ compatibility? Just having a blessed > > method of doing accessor method things will buy more source > > flexibility. The KBI can stay the same in the default case and IMHO > > this kind of thing gives developers more power to do smart invariant > > and debugging things. >=20 > KBI compatibility requires very little discipline and makes loadable > modules for network drivers much less hellish. Inlines, macros and > full visibility of ifnet in -current may be useful, but unless there's > a performance reason for doing so, retaining KBI compatibility *and* > the ability to merge ifnet changes to -stable sounds pretty nice to > me. >=20 > > Being able to say "inform me every time an interface flag changes" > > would actually be kind of nice when debugging some of the issues i've > > been facing with ath. I've been half tempted to do this -inside- the > > ath driver, partially to restore the OS portability it once tried to > > achieve. >=20 > I think that it is rare that this is useful in debugging, and > something of a red herring. Even invariants are almost a red herring: > really, we shouldn't be using these individual methods to tweak > structure fields, either, we should have a way of describing a network > driver more semantically, such that the invariants are richer and also > not as complicated, and also more comprehensive. >=20 > Source compatibility is the biggest win, but a little self-discipline > to win what measure of binary compatibility we can seems perfectly > sensible. >=20 > (And at some point, we could even replace ifnet with something that's > less of a strange grab bag assortment that's awkward to explain to new > driver writers, and keep both source and binary compatibility for a > reasonable period in doing so. Unlikely to happen in the near term, > but wouldn't it be nice? You could take a look how mutexes or vm_page_locks are handled, giving inlines for kernel proper and stable KBI for modules. --4Epv4kl9IRBfg3rk Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk9DXwUACgkQC3+MBN1Mb4hsFwCgr0yi86G8vk6twSzE8mOuIVNU f4AAoIYmqYiON5SYsi8i4//VuYsrEN37 =xETU -----END PGP SIGNATURE----- --4Epv4kl9IRBfg3rk--
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