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From: mangler@cit-vax.Caltech.Edu (System Mangler)
Newsgroups: net.unix-wizards
Subject: Re: readv(), writev()
Message-ID: <1037@cit-vax.Caltech.Edu>
Date: Sun, 12-Oct-86 03:37:53 EDT
Article-I.D.: cit-vax.1037
Posted: Sun Oct 12 03:37:53 1986
Date-Received: Sun, 12-Oct-86 13:42:47 EDT
References: <4251@brl-smoke.ARPA> <1035@cit-vax.Caltech.Edu>
Organization: California Institute of Technology
Lines: 12
Summary: readv, writev broken on raw device

In article <1035@cit-vax.Caltech.Edu>, I write:
> On raw devices, physio() generates a physical I/O for each element
> of a readv() or writev().

I was wrong; only one I/O is generated, because readv() and writev()
on the raw device won't do more than a single iovec, due to bugs in
physio().  4.3bsd fixes one of the bugs, but there's still at least
one bug left:  writev() fails on the second iovec, with errno=ENXIO.

If readv() and writev() were useful, someone would have fixed this.

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers}!cit-vax!speck