Re: [Intel-gfx] [PATCH v3 11/12] iommufd: Define IOMMUFD_INVALID_ID in uapi

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Wednesday, April 5, 2023 11:13 PM
> 
> On Wed, 5 Apr 2023 09:31:39 +0000
> "Liu, Yi L" <yi.l.liu@intel.com> wrote:
> 
> > > From: Alex Williamson <alex.williamson@redhat.com>
> > > Sent: Wednesday, April 5, 2023 5:01 AM
> > >
> > > On Sat,  1 Apr 2023 07:44:28 -0700
> > > Yi Liu <yi.l.liu@intel.com> wrote:
> > >
> > > > as there are IOMMUFD users that want to know check if an ID generated
> > > > by IOMMUFD is valid or not. e.g. vfio-pci optionaly returns invalid
> > > > dev_id to user in the VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl. User
> > > > needs to check if the ID is valid or not.
> > > >
> > > > IOMMUFD_INVALID_ID is defined as 0 since the IDs generated by IOMMUFD
> > > > starts from 0.
> > > >
> > > > Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> > > > ---
> > > >  include/uapi/linux/iommufd.h | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> > > > index 98ebba80cfa1..aeae73a93833 100644
> > > > --- a/include/uapi/linux/iommufd.h
> > > > +++ b/include/uapi/linux/iommufd.h
> > > > @@ -9,6 +9,9 @@
> > > >
> > > >  #define IOMMUFD_TYPE (';')
> > > >
> > > > +/* IDs allocated by IOMMUFD starts from 0 */
> > > > +#define IOMMUFD_INVALID_ID 0
> > > > +
> > > >  /**
> > > >   * DOC: General ioctl format
> > > >   *
> > >
> > > If allocation "starts from 0" then 0 is a valid id, no?  Does allocation
> > > start from 1, ie. skip 0?  Thanks,
> >
> > yes, it starts from 1, that's why we can use 0 as invalid id.
> 
> So the comment is wrong, correct?

yes.

Regards
Yi Liu