> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Thursday, July 27, 2023 10:43 PM
>
> On Thu, Jul 27, 2023 at 07:57:57AM +0000, Tian, Kevin wrote:
> > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > > Sent: Monday, July 24, 2023 7:00 PM
> > >
> > > @@ -252,11 +258,20 @@ struct iommu_iotlb_gather {
> > > * @remove_dev_pasid: Remove any translation configurations of a
> specific
> > > * pasid, so that any DMA transactions with this pasid
> > > * will be blocked by the hardware.
> > > + * @hw_info_type: One of enum iommu_hw_info_type defined in
> > > + * include/uapi/linux/iommufd.h. It is used to tag the type
> > > + * of data returned by .hw_info callback. The drivers that
> > > + * support .hw_info callback should define a unique type
> > > + * in include/uapi/linux/iommufd.h. For the drivers that do
> > > + * not implement .hw_info callback, this field is
> > > + * IOMMU_HW_INFO_TYPE_NONE which is 0. Hence, such
> drivers
> > > + * do not need to care this field.
> >
> > every time looking at this field the same question came out why it is
> required
> > (and looks I forgot your previous response).
> >
> > e.g. why cannot the type be returned in @hw_info():
> >
> > void *(*hw_info)(struct device *dev, u32 *length, int *type);
>
> u32 *type
>
> > NULL callback implies IOMMU_HW_INFO_TYPE_NONE.
>
> If every one of these queries has its own type it makes sense
>
> Though, is it not possible that we can have a type for the entire
> driver?
>
sure. I just prefer to introducing new field only when it's strictly
necessary.
