Date: Mon, 26 Jun 2006 08:41:36 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: freebsd-arch@freebsd.org Subject: Re: Accessing disks via their serial numbers. Message-ID: <20060626064136.GD8499@garage.freebsd.pl> In-Reply-To: <20060625.174838.2140534929.imp@bsdimp.com> References: <20060624174331.GB2134@garage.freebsd.pl> <20060625.174838.2140534929.imp@bsdimp.com>
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On Sun, Jun 25, 2006 at 05:48:38PM -0600, M. Warner Losh wrote:
> In message: <20060624174331.GB2134@garage.freebsd.pl>
> Pawel Jakub Dawidek <pjd@freebsd.org> writes:
> : I'd like to extend glabel(8) to create providers related to disks based
> : on their serial numbers and everntually driver name.
> : For example disk ad0 could also be accessed via /dev/disk/ata/3JX0LMGA
> : (/dev/disk/<driver>/<serial> or /dev/disk/<serial>).
>=20
> /dev/disk/ad/3JX0LMGA or /dev/disk/da/3JX0LMGA is the only thing
> you'll be able to do. There's no mapping from the dev_t -> device_t,
> so you have no way of knowing what the parent of the disk's dev_t.
> All the I/O in the system is done with dev_t's.
Some drivers use disk(9) for their own, so we could have:
/dev/disk/{ad,da,aac,amr,ida,ips,mlx,pst,twe,mfi}/<serial>
(if I understand things right)
But I'm not convinced about driver's name. If I've two controllers in
the system and will connect the same disk to a different driver I'd like
to be able to access it using the same name. That's the whole point,
right?
> If all the dev_t's had a device_t, then we could hang this information
> off of devd. It could create whatever links you wanted when the
> device appeared, and remove them when it disappeared. There'd really
> be no need to have geom involved at all :-).
>=20
> : It could be eventually useful to be able to ask the disk which
> : attributes it has, so we can fetch them in a loop. With BIO_GETATTR we
> : don't know which attributes provider can return.
>=20
> device_t's already have a number of bundles of attributes. It would
> seem a shame to reinvent another mechnamism.
And what if I'd like to export a serial from gmirror, which has no
device_t nor dev_t (at least not controlled by me)?
--=20
Pawel Jakub Dawidek http://www.wheel.pl
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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