Re: [PATCH 003/117] Staging: hv: Add struct hv_vmbus_device_id to mod_devicetable.h

Greg KH
2011-08-24T03:08:57Z

On Wed, Aug 24, 2011 at 12:44:38AM +0000, KY Srinivasan wrote:
>
>
> > -----Original Message-----
> > From: Greg KH [mailto:greg@kroah.com]
> > Sent: Tuesday, August 23, 2011 6:42 PM
> > To: KY Srinivasan
> > Cc: gregkh@suse.de; linux-kernel@vger.kernel.org;
> > devel@linuxdriverproject.org; virtualization@lists.osdl.org; Haiyang Zhang
> > Subject: Re: [PATCH 003/117] Staging: hv: Add struct hv_vmbus_device_id to
> > mod_devicetable.h
> >
> > On Fri, Jul 15, 2011 at 10:45:51AM -0700, K. Y. Srinivasan wrote:
> > > In preparation for implementing vmbus aliases for auto-loading
> > > Hyper-V drivers, define vmbus specific device ID.
> > >
> > > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> > > ---
> > > include/linux/mod_devicetable.h | 7 +++++++
> > > 1 files changed, 7 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/include/linux/mod_devicetable.h
> > b/include/linux/mod_devicetable.h
> > > index ae28e93..5a12377 100644
> > > --- a/include/linux/mod_devicetable.h
> > > +++ b/include/linux/mod_devicetable.h
> > > @@ -405,6 +405,13 @@ struct virtio_device_id {
> > > };
> > > #define VIRTIO_DEV_ANY_ID 0xffffffff
> > >
> > > +/*
> > > + * For Hyper-V devices we use the device guid as the id.
> > > + */
> > > +struct hv_vmbus_device_id {
> > > + __u8 guid[16];
> > > +};
> >
> > Why do you not need a driver_data pointer here? Are you sure you aren't
> > ever going to need it in the future? Hint, I think you will...
>
> I am not sure I am following you here; the guid is the device ID and it is
> guaranteed to remain the same. What is the driver _data pointer here
> you are referring to here. While some device id have the _data pointer,
> there are others that don't - for instance struct virtio_device_id. In
> our case, I am not sure how I would use this private pointer.

You use it like all other drivers use it, only if needed.

Hint, I think you need to use it in your hv_utils driver, it would
reduce the size of your code and simplify your logic.

And yes, not all bus types use it, but most do, for good reason.

greg k-h