From: Kevin Wolf <kwolf@redhat.com>
To: Wen Congyang <wency@cn.fujitsu.com>
Cc: qemu-block@nongnu.org, Fam Zheng <famz@redhat.com>,
qemu-devl <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] Question about block driver
Date: Thu, 30 Apr 2015 11:52:01 +0200 [thread overview]
Message-ID: <20150430095201.GB3368@noname.redhat.com> (raw)
In-Reply-To: <5541F934.8010100@cn.fujitsu.com>
Am 30.04.2015 um 11:43 hat Wen Congyang geschrieben:
> On 04/30/2015 05:33 PM, Kevin Wolf wrote:
> > [Cc: qemu-block]
> >
> > Am 30.04.2015 um 11:11 hat Wen Congyang geschrieben:
> >> Some drivers use bdrv_open, while the other dirvers use bdrv_file_open().
> >> What is the difference between bdrv_open() and bdrv_file_open()?
> >
> > bdrv_file_open() is used by protocol drivers that don't need any other
> > driver to work (e.g. raw-posix), bdrv_open() is used by format drivers
> > that need a bs->file (e.g. raw or qcow2).
> >
> > They used to have different parameters originally, but nowadays that's
> > the only difference.
>
> So, if the driver wants to open bs->file itself, it should use bdrv_file_open(),
> and the driver wants bs->file has already been opened before its open, it should
> use bdrv_open(). Is it right?
Yes, that's how it works, even though I don't think a driver exists that
opens bs->file by itself.
Kevin
next prev parent reply other threads:[~2015-04-30 9:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-30 9:11 [Qemu-devel] Question about block driver Wen Congyang
2015-04-30 9:33 ` Kevin Wolf
2015-04-30 9:43 ` Wen Congyang
2015-04-30 9:52 ` Kevin Wolf [this message]
2015-04-30 15:46 ` Stefan Hajnoczi
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