> From: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Sent: Wednesday, April 5, 2023 5:01 AM
>
> On Sat, 1 Apr 2023 07:44:28 -0700
> Yi Liu <yi.l.liu@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> > 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.
Regards,
Yi Liu
