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

[Alex Williamson <alex.williamson@redhat.com>]

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,

Alex