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Re: [libvirt] [PATCH 4/9] Public API Implementation



On Tue, Jan 19, 2010 at 07:40:14PM +0000, Daniel P. Berrange wrote:
> On Thu, Jan 14, 2010 at 10:42:41AM -0700, Jim Fehlig wrote:
> > Implementation of public API for virDomain{Attach,Detach}DeviceFlags.
> > ---
> >  src/libvirt.c |  106 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
> >  1 files changed, 98 insertions(+), 8 deletions(-)
> > 
> > diff --git a/src/libvirt.c b/src/libvirt.c
> > index 1145561..77f76bc 100644
> > --- a/src/libvirt.c
> > +++ b/src/libvirt.c
> > @@ -5129,7 +5129,6 @@ error:
> >  int
> >  virDomainAttachDevice(virDomainPtr domain, const char *xml)
> >  {
> > -    virConnectPtr conn;
> >      DEBUG("domain=%p, xml=%s", domain, xml);
> >  
> >      virResetLastError();
> > @@ -5147,17 +5146,63 @@ virDomainAttachDevice(virDomainPtr domain, const char *xml)
> >          virLibDomainError(domain, VIR_ERR_OPERATION_INVALID, __FUNCTION__);
> >          goto error;
> >      }
> > +
> > +    return virDomainAttachDeviceFlags(domain, xml,
> > +                                      VIR_DOMAIN_DEVICE_MODIFY_LIVE);
> > +
> > +error:
> > +    virDispatchError(domain->conn);
> > +    return -1;
> > +}
> 
> This looks safe, but there's a subtle problem with changing the existing
> virDomainAttachDevice() entry point to call virDomainAttachDeviceFlags().
> It will break compatability with old libvirtd, even though the old
> libvirtd supports the virDomainAttachDevice() code. So we need to keep
> the distinct paths in the public API & driver definitions. The eventual
> low level hypervisor drivers can of course just turn their existing
> impl into a thin wrapper to the new method..

There's one other option actually - we could put compatability code in
the remote driver client instead. Either, make it always invoke the old
RPC call if flags == VIR_DOMAIN_DEVICE_MODIFY_LIVE, or have it invoke
the new RPC call & fallback to the old RPC call if it gets an error
indicating the new one doesn't exist.

Daniel
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