Date: Sat, 14 Jul 2001 16:00:05 -0700 From: Peter Wemm <peter@wemm.org> To: mjacob@feral.com Cc: Bruce Evans <bde@zeta.org.au>, Jim Bryant <kc5vdj@yahoo.com>, scsi@FreeBSD.ORG Subject: Re: oddity with dump(8) or sa(4) in -current Message-ID: <20010714230005.14DC6380B@overcee.netplex.com.au> In-Reply-To: <Pine.BSF.4.21.0107130934370.74809-100000@beppo>
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Matthew Jacob wrote:
>
>
> On Fri, 13 Jul 2001, Bruce Evans wrote:
>
> > On Thu, 12 Jul 2001, Matthew Jacob wrote:
> >
> > > On Thu, 12 Jul 2001, Jim Bryant wrote:
> > > > On a side note, what happened to the "raw" device nodes [/dev/*rsa*]? I
'm guessing that the lack of "raw" nodes doesn't make a diff,
> > > > as /dev/*sa* are all character-mode devices.
> > >
> > > No, all devices are block devices now. Linux has no raw, FreeBSD has no
> > > cooked. Feh.
> >
> > No. No devices are block devices now (or yesterday; block devices
> > went away in 4.0). Linux has no character disk devices; FreeBSD has
> > no block disk devices. Feh. Tapes are a little different from disks.
>
> Really? I'll have to tell the ANSI SCSI committee!
He means *buffered* devices (aka block, using bdevsw, and the buffer cache)
went away. Raw devices (aka character, using cdevsw, but going direct to
the device) are what we kept. Raw devices are accessible depending on the
backing device.. eg: must be block sized transfers/seeks/etc for things
like tapes/disks/etc, but can be any for things like frame buffers.
Buffered (block, cached) can be written on any size/alignment and can be
seeked for disks. We have not had the gross B_TAPE flag for some time that
was used to stop the buffer cache getting too creative with the tape
strategy routines (ie: doing random IO).
Unix stat(2) calls raw devices "character" and buffered devices "block",
even though raw devices can be both block or byte addressable and
buffered devices enabled character/byte IO. :-) Hence the tangled up
terminology.
Cheers,
-Peter
--
Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
"All of this is for nothing if we don't go to the stars" - JMS/B5
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