Date: Mon, 06 Jun 2016 05:59:32 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Warner Losh <wlosh@bsdimp.com> Cc: KILOREUX Emperex <kiloreux@gmail.com>, Koop Mast <kwm@freebsd.org>, eadler@freebsd.org, =?utf-8?Q?Jean-S=C3=A9bastien_P=C3=A9dron?= <dumbbell@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: API to link sysctl nodes to devices Message-ID: <22384.1465192772@critter.freebsd.dk> In-Reply-To: <070D3C32-9631-49AD-85FB-53A4865AFA08@bsdimp.com> References: <CAN1JrQ2dd0WZi0_aaNdqH9xdy292tP2DYLxvKV9bfK93vYFLXw@mail.gmail.com> <13621.1465030369@critter.freebsd.dk> <CAN1JrQ1eSr3%2BrPuF5d6USX=V_cTjzuAG=VXd7pFphO%2BEk2gE%2BQ@mail.gmail.com> <070D3C32-9631-49AD-85FB-53A4865AFA08@bsdimp.com>
next in thread | previous in thread | raw e-mail | index | archive | help
-------- In message <070D3C32-9631-49AD-85FB-53A4865AFA08@bsdimp.com>, Warner Losh = write s: >One way to do this would be dev.uftdi.0.%devnodes: ttyU2 ttyU3, >which would require some new APIs for adding a dev_t to a device_t. >But that might be backwards. Many years ago I hacked up a "newbusfs" prototype, which cdevs under a device_t named tree in /device, sort of like what Sun did: /device/nexus0/acpi0/pcib1/xhci0/usbus0/uhub0/uhub3/ucom0 -> /dev/ucom0 I didn't particularly like it, and it doesn't solve the problem IMO, but it could be one way of doing it. The opposite would be plan-9 inspiration: Pair all cdevs with a partner offering the information: /dev/cuaU0 has /dev/cuaU0.info containing some lines of text with device_t linkage, serial numbers etc. >Of course, having a stronger coupling between device_t and dev_t would = >allow us to detect when /dev/foo isn't destroyed when the = >device_t created it gets detached. The device_t:dev_t mapping is [0...N]:[0...M], (people tend to forget things like multihomed disks) so that doesn't really work. >As for sysctl, there's already a sysctl tree that's = >tightly coupled to a device instance that any device can take advantage = >of. I'm not sure what you need here, unless it's what I = >described in the last paragraph. I think sysctl needs backpressure, it has exploded from a specialized place for "root only handles" to a general dumping ground. In particular it has a useless "all or nothing" attitude to jails. -- = Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe = Never attribute to malice what can adequately be explained by incompetence= .
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?22384.1465192772>