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

[Greg KH]

On Wed, Aug 24, 2011 at 12:44:38AM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Greg KH [mailto:greg@xxxxxxxxx]
> > Sent: Tuesday, August 23, 2011 6:42 PM
> > To: KY Srinivasan
> > Cc: gregkh@xxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > devel@xxxxxxxxxxxxxxxxxxxxxx; virtualization@xxxxxxxxxxxxxx; 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@xxxxxxxxxxxxx>
> > > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > > ---
> > >  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
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