Re: [Qemu-devel] [PATCH] block/raw-posix: use a character device if a block device is given

[Christoph Egger]

On 05/24/11 11:10, Kevin Wolf wrote:
> Am 24.05.2011 10:36, schrieb Christoph Egger:
> > On 05/23/11 16:11, Kevin Wolf wrote:
> > > Am 23.05.2011 14:34, schrieb Christoph Egger:
> > > > if given a block device, use the character device instead.
> > > >
> > > > From: Manuel Bouyer<address@hidden>
> > > > Signed-off-by: Christoph Egger<address@hidden>
> > >
> > > A useful commit message would explain why you're doing that.
> >
> > How about this:
> >
> > On NetBSD, the PV backend has to use the block device; but a
> > userland process is better with the character device interface. In
> > addition, a block device can't be opened twice; if the backend opens
> > it qemu can't and vice-versa.
>
> Hm, what PV backend? Are you talking about Xen? If so, let's make this
> clear:

Yes, it is about Xen.

> On NetBSD a userland process is better with the character device
> interface. In addition, a block device can't be opened twice; if a Xen
> backend opens it, qemu can't and vice-versa.
>
> > > > diff --git a/block/raw-posix.c b/block/raw-posix.c
> > > > index 6b72470..d05f373 100644
> > > > --- a/block/raw-posix.c
> > > > +++ b/block/raw-posix.c
> > > > @@ -136,11 +143,45 @@ static int64_t raw_getlength(BlockDriverState *bs);
> > > >     static int cdrom_reopen(BlockDriverState *bs);
> > > >     #endif
> > > >
> > > > +#if defined(__NetBSD__)
> > > > +static const char *raw_get_rawdevice(const char *filename)
> > > > +{
> > > > +    static char namebuf[PATH_MAX];
> > > > +    const char *dp = strrchr(filename, '/');
> > > > +
> > > > +    if (dp == NULL) {
> > > > +        snprintf(namebuf, PATH_MAX, "r%s", filename);
> > > > +    } else {
> > > > +        snprintf(namebuf, PATH_MAX, "%.*s/r%s",
> > > > +            (int)(dp - filename), filename, dp + 1);
> > > > +    }
> > > > +    fprintf(stderr, "%s is a block device", filename);
> > > > +    filename = namebuf;
> > > > +    fprintf(stderr, ", using %s\n", filename);
> > >
> > > Not sure if fprintf is a good idea here, but ok.
> >
> > I want to make it clear what file the qemu process has been
> > using. this is what log files are for, isn't it ?
>
> Yeah, while I don't like fprintfs in block driver code, I do agree that
> it makes some sense here.
>
> Kevin


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